Friday, December 14, 2012

Small-sided games: what’s new?
Fradua and colleagues from the University of Granada, Spain, recently published a study in the Journal of Sports Science (2012) the findings of which may have practical applications for training. Four 1st Spanish league matches involving five different teams were analyzed during the 2002-3 season using a match analysis system. The length and width of the rectangle that included all outfield players was defined with a software. Briefly, the rectangles were composed by two vertical lines parallel to the goal and two parallel lines to the touchlines. The field was divided in six zones. Zone 1 was the closest to the goal of the team in possession of the ball and zone 6 was the nearest to the opponent’s goal. The individual area of the small-sided games was calculated by dividing the pitch size by 20 (the number of outfield players).

What they found
  • Individual playing area ranged from 79 to 94 m2 and varied with the playing zone.
  • Length to width ratio of the areas ranged between 1:1 and 1:1.3. Length to width ratio was 1:1 in zones 1, 2, 5 & 6 and 1:1.3 in zones 3 and 4.

These findings may help the coaches to apply more specific small-sided games that will more closely mimic real game situations.

Points to remember
These finding have been derived from 1) four matches with five teams only, 2) teams with a specific style of play.

Fradua et al. Designing small-sided games for training tactical aspects in soccer: extrapolating pitch sizes from full-size professional matches. Journal of Sport Science, 2012; Nov 28. [Epub ahead of print]

Monday, November 26, 2012

How to evaluate the recovery ability of your players
As discussed in the last week’s post the ability to recover fast after a match or a training session is critical to the player’s career pathway as well as to the team’s performance. Ideally, we are looking for players who can perform at the highest level during the match & recover fast so they are ready to perform high in the next match.
Practical steps to define your players’ ability & speed up recovery
1)      Identify the recovery pattern of your player. To do so you must evaluate certain parameters before and several hours/days after a match. There are many performance (sprints, vertical jumps, football specific endurance tests etc.) and non-performance related tests used in the literature (CK levels, mood state, sleep quality, delayed-onset muscle soreness questionnaires etc.).
2)      Better to follow a holistic approach. Answer the “why” before you choose the tests.
3)      Discuss with players and other staff in the club and develop a recovery strategy. From the variety of methods adopt those that
a.       Are science based
b.      Your players like the most
4)      Re-evaluate your players as you did in stage 1. Try to do that under similar, if possible, conditions. Then you will be able to make a conclusion on which method is more effective for your player.
5)      Look more to the individual rather than to the team as a whole. Try to find out what is suitable for every player. If you improve the player you will finally improve the team.

Saturday, November 17, 2012

Is the 3-4 days recovery time between matches sufficient to restore performance?

In elite soccer, the number of matches per year, including domestic league and cup and international matches is very high. The number increases for the players of the national team. At certain periods, it is common for the teams to compete every 72-96 hours. As a result players may experience fatigue and be at a higher risk for a muscle injury.
Is that true?
There are at least two studies which have examined the role of the number of matches played on performance and injury rate. Dupont and colleagues (2010) from Lille University, France, and Celtic Lab, analyzed the effect of 2 matches per week on physical performance and injury rate in elite soccer players. The authors monitored match-related physical performance and injuries during 2 seasons for 32 professional players. Total distance covered, high-intensity distance, sprints number and distance was not affected by the number of matches per week (1 versus 2). However, the injury rate was about 6-fold higher when players played 2 matches per week.
In another study, Ekstrand and colleagues (2004) grouped the national team players according to the number of matches played during the 10 weeks before the World Cup 2002. The performance of the players during the World Cup was evaluated by a group of 3 international experts. The analysis showed that the players who underperformed played more matches during the 10 weeks before the World Cup than those who performed better than expected. This is of course contradictory to the previous study and underlines the need for more research and critical thinking.
At high level, the 72-96 hours of recovery between 2 matches might be sufficient to maintain physical performance. However, football performance might be negatively affected. To things to remind 1) It is worth noting that the results of both studies mentioned above are with elite players 2) results might have been affected by several factors such as the recovery techniques etc.
Practical applications
  • The higher the level of the players and hence their fitness level the greater the chances to play 2 matches every 72-96 hours without a significant decline in their physical performance.
  • We don’t know if this holds for lower level players.
  • Although physical performance might not be affected it seems that football performance might be lower than expected with high number of games. Again, this was observed during the World Cup which normally is being held at the end of the season and this should be kept in mind before making conclusions.
  • The ability to recover fast is crucial especially at the high level. This ability seems to be positively affected by a number of factors, among others:
    • high aerobic fitness
    • effective recovery techniques which include proper diet, sleep, physical and mental regeneration
It seems that the rate of recovery is affected by many parameters and is a very much an individual issue. Hence, first task is to develop the individual pattern of recovery after the match!

Dupont et al. Effect of 2 soccer matches in a week on physical performance and injury rate. Am J Sports Med 38:1752-1758, 2010.
Ekstrand et al. A congested football calendar and the wellbeing of players: correlation between match exposure of European footballers before the World Cup 2002 and their injuries and performances during that World Cup. Br J Sports Med 38: 493-497, 2004.

Saturday, November 10, 2012

Preparation for the World Cup 2022

World Cup 2022 is not far ahead. Qatar will be the first country from the Middle East to host such a big event. The preparation has already started! Watch the videos presenting the vision of the State of Qatar to host the best event ever.

Saturday, October 27, 2012

Hamstring injuries prevention: an update

Last week I had the opportunity to attend the presentation by Professor Roald Bahr on recent evidence on hamstrings injury prevention. Professor Bahr is a leading sports medicine physician in the area with a lot of clinical and research work. I have coded the key points of his presentation by giving answers to the questions I assume most of us would have.
Is hamstrings injury an important issue in football (soccer)?
Yes, it is. Injury of the hamstrings is the most common injury type in football (12-16% of all injuries). Re-injury rate is relatively high and this should be taken into account in screening as well as during rehabilitation.
What is the mechanism of hamstrings injury?
From the video analysis studies, it appears that hamstring injuries usually occur during rapid acceleration, deceleration, change of direction or during the last part of the swing phase of gait. This phase is where hamstrings are working eccentrically.
Which are the main risk factors for hamstring injuries?
Although not clear, many factors are involved in the aetiology of the hamstrings injuries. These are grouped into intrinsic (age, previous injury history, fatigue etc) and extrinsic factors (lack or inappropriate warm-up, surface, temperature etc). There is strong evidence in the literature that players with advanced age and/or previous hamstrings injury are at a higher risk for hamstrings injury in the future. There might also be factors we still don’t know or we know very little involved in this type of injury occurrence.
Are low flexibility and large muscle imbalances associated with increased hamstring injury risk?
It is not clear so far. While some studies show a relationship between greater flexibility and lower injury risk others have failed to replicate these findings. The same holds for muscle imbalances. It is not to say that players do not need to improve their range of motion. It seems however, that above a threshold there is no additional protection for future injuries with improvements in flexibility.
Which is the recommended injury prevention programme by Prof Bahr and his team?
Prof Bahr and his group have done a lot of research on the Nordic exercise effect on hamstrings injury prevention. Their studies have shown that training the muscles regularly with this exercise has reduced the hamstrings injury occurrence.

Some details and recommendations for the programme
According to Prof Bahr it is important that the exercise is executed in the right way. Right execution of this exercise requires the coach to push the player downward at the start of exercise. At this stage the players execute resistance. Players should start with few repetitions once or twice a week and increase the training load and/or frequency progressively. Data have shown that players feel no pain the day after the Nordic exercise training provided the overload principle is followed.
Is Nordic exercise suitable for youth players?
Professor Bahr answered that although there is no related research, Nordic exercise could be used by 15 years and older players in order to better prepare them for the future training loads.
Some remarks
Nordic exercise is only an example of easy-to-use exercise for hamstrings injuries prevention. Strength & conditioning coaches should follow a holistic approach and bear in mind that players need to be trained for other muscle groups too. From the sports science perspective, fitness training for injury prevention should take into account, among others, the:
  • Injury history each player
  • Individual characteristics

Take-home messages (by the blog owner)
Nordic exercise is a good tool for hamstrings injury prevention. Coaches should follow a holistic approach and include evidence-based exercises that fit the group and the individual needs.
For more reading
Arnason et al. Risk factors for injuries in football. Am J Sports Med 32: 5S-16S, 2004.
Croisier et al. Strength imbalances and prevention of hamstring injury in professional soccer players: a prospective study. Am J Sports Med 36: 1469-1475, 2008.
Engebretsen et al. Intrinsic risk factors for hamstring injuries among male soccer players: a prospective cohort study. Am J Sports Med 38: 1147-1153, 2010.
Petersen et al. Preventive effect of eccentric training on acute hamstring injuries in men's soccer: a cluster-randomized controlled trial. Am J Sports Med 2011 Nov;39(11):2296-303
van Beijsterveldt et al. Risk factors for hamstring injuries in male soccer players: a systematic review of prospective studies. Scand J Med Sci Sports 2012 Jun 21. doi: 10.1111/j.1600-0838.2012.01487.x. [Epub ahead of print].
Witvrouw et al. Muscle flexibility as a risk factor for developing muscle injuries in male professional soccer players. A prospective study. Am J Sports Med 31: 41-46, 2003.

Friday, October 19, 2012

What do you leave behind?

Laliza, Ioannina

Watch the video from an inspirational talk by Professor Tim Noakes at TEDxCape

Friday, October 5, 2012

Sports Science and Football: what's new?
Today, I would like to present some abstracts from the last Congress of the European College of Sports Science (Belgium, July 2012). In general, many studies, more than 2000 participants and a nice city (Bruges). What I have tried to do below is to group the most interesting studies into:
  • ·         Physiology
  • ·         hot methods & new equipment
  • ·         Injury prevention
  • ·         High intensity intermittent training

Ring-Dimitriou et al
University of Salzburg

Beside exercise prescription single-nucleotide polymorphism (SNP) in genes important for mitochondria function such as PPARGC1A and PPARD have been reported to affect the change in anaerobic threshold in a retrospective study (Stefan et al., 2007). Therefore we prospectively investigated a 10-wk training response of men with SNP in these genes. Methods Genotyping (TaqMan, ABI7900HT) was performed in 838 sedentary males for SNP in PPARGC1A (rs8192678) and PPARD (rs2267668). After intervention (supervised 10 wks cycling, 3x 60 min, HR@70-90% VO2peak) n=28 remained for post tests (59±7 yrs, 27.6±4.1 kg/m² BMI, 36.3±6.9 ml/kg/min VO2peak). Subjects were assigned to wild type (WT=13), SNP1 (minor risk allele for PPARGC1A, WT for PPARD, n=6), and SNP2 (risk alleles for both genes, n=9). Trainability was determined as the relative change in work rate P@VT (point of optimal respiration), P@AT (anaerobic threshold), and P@RCP (respiratory compensation point) based on gas exchange analyses (ZAN680, nSpire Health, US) during incremental cycling (Ergoline, Schiller). Mean differences within and between groups were determined by ANOVA with p<0.05. The study was approved by the Salzburg Ethics Committee and funded by National Bank of Austria (J14156). Results Significant differences were found within WT in P@VT (99±21 vs. 122±19 W, p=.005) and @RCP (155±25 vs. 185±29 W, p=.009) only. P@RCP was significantly lowest in SNP1 compared to SNP2 and WT (%, 3±9 vs. 12±5 vs. 20±15; F=4.6, p=.02). VO2@VT and @RCP were significantly lower in SNP1 and SNP2 compared to WT (%, 2±10 vs. 4±13 vs. 18±15, F=3.6, p=.04, and 0±8 vs. 6±5 vs. 17±16 vs., F=4.8, p=.02, respectively). Discussion In line with the findings of Stefan et al. (2007), we found a diminished exercise effect at sub maximal performance level of untrained males with SNPs. The short-term response at these levels of >15% in WT was sufficient compared to other reports (Skinner et al., 2001) and could probably serve as trainability markers regarding to Vollaard et al. (2009). Although the power of our study is limited due to sample size and sex selection, our data indicate that the trainability of aerobic performance could be affected by gene variants.

Parise, G.
McMaster University, Canada

The role of muscle stem cells (satellite cells) in promoting muscle growth and adaptation in humans has largely been understudied. Nonetheless, excellent work has been reported by groups from around the world. The fact that a satellite cell response is triggered following an acute bout of exercise is generally accepted as fact. What remains a significant point of contention is whether or not satellite cells play a role in promoting growth in adulthood. Additionally, very little is known about the regulatory mechanisms that govern satellite cell function and fate. Over the last five years we and others have made a significant effort to reveal regulatory mechanisms that may govern satellite cell activation, proliferation and differentiation in humans. Modest progress has been made, however the regulatory mechanisms that drive the satellite cell response in humans are now being revealed. To date we have identified key roles for myostatin in
the activation of satellite cells following exercise and IL6 in the proliferation of satellite cells. We have also identified how these factors are affected by age in their ability to promote satellite cell activation and proliferation. Collectively, we are just beginning to appreciate the complex regulatory mechanisms that govern human satellite cell function.

Ando, S.
Fukuoka University

Vision is one of the most important sensory modalities in humans. The visual field is defined as the area perceived by the eyes while people fixate on a point, and is composed of the central and peripheral visual fields. Many sports require high-level visual perceptual skills under conditions of physiological stress. In sports such as football, players gather visual information from the periphery of the visual field to see other players and objects beyond the central visual field. Thus, peripheral visual perception may play an important role in sports performance. In recent years, increasing empirical evidence suggests that acute exercise affects peripheral visual perception. A behavioral study has shown that peripheral visual perception may be vulnerable to exercise as compared with central visual perception (Ando et al. 2008). The following study suggested that the detrimental effects of exercise on peripheral visual perception are not primarily ascribed to low visual resolution, but to the impaired top-down control of visual attention (Ando et al. 2012). During incremental exercise, peripheral visual perception was impaired when engaged at exercise at high workloads above the ventilatory threshold (Ando et al. 2005). Furthermore, high aerobic capacity attenuated the increase in peripheral visual reaction time during strenuous exercise, suggesting that oxygen availability play a role in peripheral visual perception (Ando et al. 2005). Peripheral visual perception was impaired to some extent during exercise under mild hypoxia relative to normoxia although the differences between normoxia and hypoxia failed to reach statistical significance (Ando et al. 2010). Further analysis demonstrated that decreases in cerebral oxygenation were closely associated with the impairment in peripheral visual perception during exercise (Ando et al. 2010). In contrast, peripheral visual perception was not impaired even during strenuous exercise under hyperoxia where oxygen availability was elevated (Ando et al. 2009). These findings suggest that a decrease in cerebral oxygenation is associated with impairment in peripheral visual perception during strenuous exercise. The decrease in cerebral oxygenation during exercise means that oxygen availability may be insufficient to meet metabolic demand. It is plausible that decreases in cerebral oxygenation have detrimental effects on visual perceptual performance during exercise.

Novel methods/equipments
Poppendieck et al.
Saarland University, Saarbrücken, Germany

Cooling after exercise has been suggested as a method to improve recovery during intensive training periods or competitions lasting several days to weeks. It has been investigated in various studies and has also found its way into practice. However, many existing studies include untrained subjects to induce a higher degree of muscle soreness and fatigue due to a reduced fitness level. It is not clear if the results of those studies can be transferred to trained athletes. Although recent review articles on the topic of cooling and recovery exist, none of those has focused especially on trained athletes [Halson, 2011; Leeder et al., 2011]. The purpose of this work was to fill this gap. Methods A literature search was conducted using the following databases: PubMed, ISI Web of Science, AMED and EMBASE. Inclusion criteria were: a) explicit analysis of trained subjects, b) cooling after exercise, c) performance measurement, d) existence of a control group or condition, e) performance evaluation at least 2 h after cooling to exclude potential precooling effects. In total, 14 studies with 153 subjects were located and analyzed. For all studies, the effect of cooling on performance was determined, and effect sizes (Hedges’ g) were calculated. In order to determine under which circumstances cooling may be most beneficial, several parameters of the study design were more closely examined. Regarding performance measurement, the best effects were found for endurance parameters (3 studies/30 subjects, 3.7%, g=0.35), while for jump (3/35, 3.4%, g=0.13), strength (10/113, 2.4%, g=0.12) and sprint performance (4/46, 2.7%, g=0.10), effects were smaller. The effects were most pronounced when performance was evaluated 48 h after exercise (7/71, 5.0%, g=0.34). With respect to the exercise which was used to induce fatigue, effects after strength training (4/39, 3.6%, g=0.18) were slightly larger than after endurance-type exercise (10/114, 2.2%, g=0.16). Cold water immersion (10/117, 2.9%, g=0.19) and cryogenic chambers (2/18, 3.8%, g=0.14) seemed to be more beneficial than cooling packs (2/18, 0.3%, g=0.00). Overall, the effects of cooling on recovery were rather small (2.8%, g=0.17). Under appropriate conditions, however, cooling after exercise may have relevant positive effects on performance recovery of trained athletes.

Halson et al.
AIS Performance Recovery (Canberra, Australia)

Although cold water immersion is beneficial for recovery between bouts of high-intensity exercise, it may impair long term performance by attenuating the stimuli responsible for adaptation to training. Here we report a comparison of effects of cold-water immersion and passive rest on performance over a 39-day training block. Methods Thirty-four male endurance-trained competitive cyclists were randomized to cold water immersion or control (no recovery) groups for a simulated cycling grand tour consisting of 7 d of baseline training, 21 d of intense training, and an 11-d taper. Criteria for completion of training and testing were satisfied by 10 cyclists in the cold-water immersion group (age, 20.2 ± 1.7 y; mass, 70.9 ± 6.5 kg; maximal aerobic power, 5.13 ± 0.21 W/kg) and 11 in the control group (19.8 ± 1.7 y; 68.9 ± 8.0 kg; 5.01 ± 0.41 W/kg). Cyclists completed two sets of performance tests each week: a combination cycling test consisting of 6-s sprints (MMP1s), a series of varying intervals, and a 10-min time trial on one day, and two 4-min bouts separated by 30 min of recovery (2xMMP4m) the next day. Cold-water immersion was performed 4 times per week for 15 min at 15°C following training and testing sessions. Uncertainty in mean differences between groups in the changes in mean performance power between tests following baseline and taper periods was estimated as 90% confidence limits and evaluated probabilistically in relation to a smallest important effect on mean power of 1%. Results Cyclists in the cold water group had an unclear change in overall 4-min power relative to control (2.7%, ±5.7%); however when subtracting the power in the first effort from the second effort, the cold water group showed a clear likely beneficial effect compared with control (3.0%, ±3.8%). The change in MMP1s in the cold water group also demonstrated a clear likely beneficial effect compared to control (4.4%, ±4.2%). Observed differences between groups for the 10-min time trial were trivial but the effect was unclear (-0.4%, ±4.3%). Discussion The primary objective of this study was to evaluate whether cold water immersion during a 3-wk phase of rigorous cycling training (simulating aspects of a Grand Tour) would impair cycling performance. In summary, data from this study do not support recent speculation that cold-water immersion is detrimental to adaptations to 3 weeks of increased training load in competitive cyclists.

Faulkner et al.
Loughborough University, UK

Elevations in muscle temperature (Tm) have been shown to be important for enhancing maximal muscle power output during short duration, sprint based activities, hence the completion of a warm up prior to many exercise types. In many sporting competitions it is not uncommon for there to be delays between warm up completion and performance execution, during which time activity levels may be insufficient to maintain elevations in Tm. Excessive decline in Tm may lead to sub-optimal contractile conditions and impaired exercise performance. Therefore, the aim of the present study was to determine to what extent a delay between warm up and competition might influence Tm and performance and whether this may be attenuated using an insulated athletic trouser with optional heating. On three separate occasions, 11 male cyclists (24 ± 5yrs; 182.4 ± 7.6cm; 77.4 ± 10.0kg) completed a standardized 15 min intermittent sprint-based warm up on a cycle ergometer, followed by a 30 min passive recovery period before completing a 30 sec maximal sprint test. Tm of the vastus lateralis was measured at depths of 1, 2 and 3 cm prior to and following the warm up and immediately before the sprint test. Measures of absolute and relative peak power output were taken. During the recovery period subjects wore a tracksuit top and (in a balanced order) either i) a standard tracksuit ensemble (CONT), ii) a pair of insulated athletic trousers (INS) or iii) insulated athletics trouser with inbuilt electric heating elements around the thighs (HEAT). The warm up increased Tm at all depths by ~2.5°C, with no differences between conditions. Following the recovery period Tm declined in both CONT (1cm 36.3 ± 0.4°C; 2cm 36.6 ± 0.3°C; 3cm 36.9 ± 0.2°C) and INS (1cm 36.5 ± 0.6°C; 2cm 36.8 ± 0.4°C; 3cm 37.0 ± 0.3°C), whereas Tm for HEAT remained elevated at all depths compared to both INS and CONT (1cm 37.4 ± 0.3°C; 2cm 37.3 ± 0.2°C; 3cm 37.3 ± 0.2°C; p<0.01). Peak power output was higher in HEAT (20.9 ± 1.6 W/kg) than both CONT (19.2 ± 1.7 W/Kg; 9%, p<0.05) and INS (20.3 ± 2.3 W/Kg; 3%, p<0.05). Though insulated trousers alone were not effective, the use of an insulated athletic trouser with the addition of electric heating elements around the thighs was able to reduce the decline in Tm that is associated with forced periods of inactivity between warm up completion and competition. Furthermore, the prevention of the decline in Tm improved subsequent sprint performance compared to when passive heating is not used.

Stahn et al.
Center for Space Medicine, Charité (Berlin, Germany)

Hyperthermia has been suggested to control central fatigue by a threshold temperature (critical limiting temperature, CLT) and/or selective brain cooling, having a neuroprotective effect against lethal heat stress. Recently, however, the role of these mechanisms has been questioned (Marino 2011). Previous studies in this field have been limited to small sample sizes due to technical difficulties and inconveniences associated with core body temperature measurements such as rectal or esophageal recordings. In addition, present temperature monitoring technologies might not accurately reflect brain temperature, and specifically temperature in the hypothalamus where the center of thermoregulation is located. We therefore introduced a new non-invasive heatflux technology for determining core body temperature at the forehead (Gunga et al. 2009; Stahn et al. 2011). The aim of the present study was therefore to investigate whether there is a consistent CLT determined close to the hypothalamus during intense exercise in a large sample of young men and women with varying degrees of maximal aerobic capacity. A total of 64 young subjects (43 men, 21women) completed a graded maximal exercise until volitional exhaustion on a bicycle ergometer. In addition to oxygen uptake (breath-by-breath) core body temperature was continuously determined using a new non-invasive heatflux sensor (Double Sensor) positioned at the forehead. Average CBT at the time of exhaustion was 40.2 °C with men displaying slightly, but significantly higher CBT than women (40.3 vs. 39.9°C, P < 0.05). ANCOVA revealed that this difference could be attributed to higher maximal aerobic capacity in men. Comparing high and low fit subjects irrespective of gender demonstrated that CBT was significantly higher at submaximal (60% and 80% VO2max) and maximal exercise (40.6 vs. 39.7 °C, P < 0.001). In addition, CBT demonstrated a linear increase as a function of maximal aerobic capacity (r = 0.53; P < 0.001). While volitional exhaustion was reached around 40 °C irrespective of initial CBT and its rate of increase, suggesting a consistent CLT there was considerable variation in CBT between subjects. In addition this variation was characterized by a positive linear relationship between CBT during maximal exercise and maximal aerobic capacity. These data suggest that either subjects may adapt to higher levels of heat stress by increasing CLT or that neuroprotection from heat stress might not be the primary cause per se for the discontinuation of vigorous physical activity (Marino 2011).

Injury prevention
Impellizzeri et al.
Schulthess Clinic (Zurich, Switzerland)

To develop an injury prevention program that can be easily implemented in the everyday training routine (especially at amateur level), the FIFA Medical Assessment and Research Centre (F-MARC) has developed an advanced version of a previous prevention program: “The 11+”. A cluster randomized controlled trial has recently shown that “The 11+” is effective in reducing injuries (Soligard et al. 2008). “The 11+” is a warm-up routine designed for training some physical components: core stability, neuromuscular control and balance, eccentric training of the hamstrings, plyometric and agility. The aim of this study was to examine whether “The 11+” can improve neuromuscular control, strength and performance in amateur soccer players. Eighty-four male amateur players from 6 teams participated to this parallel, two groups, pre-post, randomized controlled trial. They were allocated to “The 11+”(n=42) and control (n=39) group using a restricted blocked randomization where each block corresponded to a team. The players had to complete the warm-up routines 3 times a week for 9 weeks. Outcome measures were: eccentric and concentric strength of flexors and extensors, star excursion balance test, time-to-stabilization, core-stability of the trunk, vertical jump, sprint, agility. Analysis was performed using mixed models and magnitude of inferences. No differences between groups were found in training load and training components (0.146 < p <0.680). Both groups completed an average of 2.1 sessions a week. After controlling for confounders and baseline values, possible worthwhile differences (47 to 72%) in favor of the 11+ group were found for flexors concentric strength at 60°/s (3.2%, 95% CI 0.6 to 5.9%; ANCOVA p level=0.046) and 180°/s (4.6%, 95%CI 1.0 to 8.3%;p=0.038), flexors eccentric strength (3.8%, 95%CI 1.4 to 6.2%;p=0.010), sprint (-0.9%, 95%CI -1.9 to 0.1%;p=0.123), agility (-1.1%, 95%CI -2.6 to 0.1%;p=0.265). Likely worthwhile differences (93-95%) in favor of “the 11+” group were found for Time-to-stabilization (-2.8%, 95%CI –4.4 to -1.2%;p=0.005) and core-stability (-8.9%, 95%CI -15 to -3%;p=0.012).The results of this study showed that nine weeks implementing “The 11+” as a routine warm-up can induce substantial improvement in neuromuscular control and possible worthwhile changes in flexors strength. Therefore, the 11+ not only can prevent injuries but can also induce positive effects on important physical components in amateur players.

High intensity intermittent training  and health
Benefits of High Intensity Intermittent Training (HIIT) in Untrained and Diseased People

Gibala, M.
McMaster University

High-intensity interval training (HIT) can serve as an effective alternate to traditional endurance-based training, inducing similar or even superior physiological adaptations in healthy individuals and diseased populations, at least when compared on a matched-work basis. While less well studied, low-volume HIT can also stimulate physiological remodeling comparable to moderate-intensity continuous training despite a substantially lower time commitment and reduced total exercise volume (1). For example, as little as six sessions of HIT over 2 wk, totaling 􀗽15 min of “all out” cycle exercise within a total training time commitment of ~2 h, increases the maximal activity of mitochondrial enzymes and improves performance during tasks that rely heavily on aerobic energy provision. These data suggest that HIT may be a potent and time-efficient strategy to induce skeletal muscle metabolic adaptations that are linked to improved health. Many low-volume HIT studies have employed relatively extreme variable-load exercise interventions (e.g., repeated Wingate Tests) that may not be safe or well tolerated by certain individuals. Recent work has shown that short-term training using a more “practical” model of HIT (e.g., 10 x 1 min repeats at 􀗽90% maximal aerobic work capacity, interspersed by 1 min of recovery) increased muscle oxidative capacity and improved endurance performance (2). Low-volume HIT studies in persons who might be at risk for cardiometabolic disorders or patients with chronic disease are very limited. However, it was recently demonstrated that low-volume HIT was effective and well tolerated in people with type 2 diabetes (3). Two weeks of HIT reduced average 24-h blood glucose concentration and postprandial glucose excursions, measured via continuous glucose monitoring under standardized diet but otherwise free-living conditions. Given that “lack of time” is the most commonly cited barrier to regular exercise participation, it is tempting to speculate that low-volume HIT may represent a time-efficient alternative to traditional endurance training. While the preliminary evidence from small, short-term studies are intriguing, large-scale studies are clearly needed to resolve whether low-volume HIT is a realistic, time-efficient exercise alternative to improve health and reduce the risk of cardiometabolic disease.

Spriet, L.
University of Gelph

It is now well established that models of high intensity intermittent training (HIIT) produce robust increases in mitochondrial volume. Mitochondrial biogenesis occurs rapidly with this training model with increased mitochondrial protein content observed after as little as 3-4 training sessions in humans. The HIIT models ask subjects to perform short bouts of exercise anywhere from ~90% VO2max for 1-4 min to all out sprints at power outputs as high as 300% of what is needed to elicit VO2max for 30 sec. These workouts are usually completed every other day. The ability to exercise at high aerobic intensities (~90% VO2max) is not surprisingly drastically improved following HIIT. Interestingly, when subjects are asked to exercise at ~60-65% of the pre-training VO2max following HIIT, the reliance on fat as a fuel in also increased. This is similar to what is seen following the classical endurance training protocols where subjects exercise for 1-2 hours/day at ~60% VO2max, 5 times a week. These results demonstrate that the HIIT exercise stress is able to activate the molecular machinery to produce the many proteins needed to increase mitochondrial volume and capacity. Numerous studies have assessed these adaptations by directly measuring either the activity and/or the protein content of enzymes and intermediates involved in the major mitochondrial pathways, including citrate synthase from the TCA cycle, cyctochrome IV from the electron transport chain, betahydroxylacyl dehydrogenase from the beta-oxidation pathway, enzymes of the electron transport shuttle into the mitochondria, and pyruvate dehydrogenase or regulatory elements of this complex. An impressive aspect of these adaptations is how rapid they occur where increases have been shown after as little as 3 HIIT workouts. HIIT also increased the amount of mitochondrial and plasma membrane fat transport proteins in human skeletal muscle. Hormone sensitive lipase activity was increased by 13% and the use of intramuscular triacylglycerol was increased by 35% during 1 hour of submaximal exercise, but these changes were not significant. The important conclusion seems to be that the high intensity exercise bouts during HIIT maximally or near-maximally activate the aerobic system at the onset of exercise and also the various molecular signals that lead to increased production of mitochondrial fat-metabolizing proteins. This leads to rapid upregulation of the pathways that metabolize fat resulting in an increase in the capacity to oxidize fat during submaximal exercise following HIIT.

Perry, C.G.R.
University of Guelph, Guelph, Ontario

Contraction signals a plethora of genomic events designed to increase the efficiency by which muscle responds to future energetic challenges. Central to this improved metabolic regulation is an increase in mitochondrial content described by Holloszy 45 years ago. This mitochondrial biogenesis is linked to lower substrate phosphorylation, carbohydrate sparing and increased fat oxidation, all of which contribute to improved endurance performance. Furthermore, Dudley et al demonstrated in the 1980’s that the rate and magnitude of mitochondrial protein accumulation during training is proportional to the training intensity. Multiple breakthroughs were then made ~15-20 years ago establishing nuclear genomic expression as the critical link between contraction and improvements in glucose uptake which later led to similar nuclear/mitochondrial genomic links for exercise-induced mitochondrial biogenesis. Initial explorations into contraction/exercise-induced gene expression by Neufer, Wasserman and others were followed by an explosion in research into the regulation of contraction-induced gene expression by transcription factors and co-activators. Most notably, the discovery of the PPAR, NRF, and PGC1 family of transcriptional regulators (and others) drastically improved our understanding throughout the last ~15 years of exercise-induced transcriptional regulation of mitochondrial biogenesis. In the past ~5 years, these same questions have been applied to HIIT in human muscle. We now possess a detailed understanding that the fast increases in mitochondrial content in human muscle during HIIT are likely mediated by multiple transcriptional regulators. Several groups have demonstrated that HIIT activates a variety of signaling cascades sensing specific signals generated during exercise which then activate transcription factors (PPARs, NRFs, etc) that are likely co-ordinated by co-activators (eg. PGC1s). These transcriptional regulators also increase in content at a rapid rate which precedes increases in mitochondrial proteins. This process requires repeated exercise sessions in order to accumulate sufficient genomic messages (mRNA) to drive translation of mitochondrial proteins at a level that sustains a greater mitochondrial content. Future studies should examine if the balance between net transcriptional repression (RIP140, etc) and activation (PGC1 regulators, etc) determines 1) the rate of mitochondrial biogenesis and 2) the onset of plateaus in protein content and performance improvements during training, with no single factor being essential but rather all cooperating to maximize the rate of adaptation. It is now clear that HIIT invokes rapid improvements in muscle energy homeostasis via a coordinated expression of multiple transcriptional programs controlling substrate uptake and catabolism. These molecular responses underscore the impressive efficacy of HIIT as a tool to stimulate robust increases in endurance performance and metabolic health in humans.

Friday, September 21, 2012

Interventions to prevent ACL injuries-Recent studies in football (Part III)

Recent studies in football –Part III
Abstracts modified from PubMed
Gagnier JJ, Morgenstern H, Chess L. Interventions Designed to Prevent Anterior Cruciate Ligament Injuries in Adolescents and Adults: A Systematic Review and Meta-analysis. Am J Sports Med. 2012 Sep 12. [Epub ahead of print]
Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, Michigan.
Anterior cruciate ligament (ACL) injuries are common, result in significant morbidity, and are expensive to repair surgically and to rehabilitate. Several randomized and observational studies have tested neuromuscular interventions as preventive measures for these injuries. The aim of this study was to conduct a systematic review and meta-analysis of all known comparative studies for estimating and testing the effect of neuromuscular and educational interventions on the incidence of ACL injuries in adolescents and adults, both male and female. Several databases were used to identify eligible studies through July 4, 2011: MEDLINE, EMBASE, SPORTDiscus, Cumulative Index to Nursing and Allied Health Literature, the Cochrane Central Register of Controlled Trials, and Health Technology Assessment. Eligible studies were assessed for risk of bias, and meta-analyses were performed on the estimated intervention effect (log incidence rate ratio) using inverse-variance weighting, subgroup analysis, and random-effects meta-regression to estimate the overall (pooled) effect and explore heterogeneity of effect across studies (measured by I(2) and tested with the Q statistic). Eight cohort (observational) studies and 6 randomized trials were included, involving a total of approximately 27,000 participants. The random-effects meta-analysis yielded a pooled rate-ratio estimate of 0.485 (95% confidence interval [CI], 0.299-0.788; P = .003), indicating a lower ACL rate in the intervention groups, but there was appreciable heterogeneity of the estimated effect across studies (I(2) = 64%; P = .001). In the meta-regressions, the estimated effect was stronger for studies that were not randomized, performed in the United States, conducted in soccer players, had a longer duration of follow-up (more than 1 season), and had more hours of training per week in the intervention group, better compliance, and no dropouts. Nevertheless, residual heterogeneity was still observed within subgroups of those variables (I(2) > 50%; P < .10).

Conclusion: Various types of neuromuscular and educational interventions appear to reduce the incidence rate of ACL injuries by approximately 50%, but the estimated effect varied appreciably among studies and was not able to explain most of that variability.

Hoier B, Nordsborg N, Andersen S, Jensen L, Nybo L, Bangsbo J, Hellsten Y. Pro- and anti-angiogenic factors in human skeletal muscle in response to acute exercise and training. J Physiol. 2012 Feb 1;590(Pt 3):595-606. Epub 2011 Dec 12.
Department of Exercise and Sport Sciences, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen, Denmark.
This study examined the effect of acute exercise and 4 weeks of aerobic training on skeletal muscle gene and protein expression of pro- and anti-angiogenic factors in 14 young male subjects. Training consisted of 60 min of cycling (60% of ), 3 times/week. Biopsies were obtained from vastus lateralis muscle before and after training. Muscle interstitial fluid was collected during cycling at weeks 0 and 4. Training increased (P < 0.05) the capillary: fibre ratio and capillary density by 23% and 12%, respectively. The concentration of interstitial vascular endothelial growth factor (VEGF) in response to acute exercise increased similarly (>6-fold; P < 0.05) before and after training. Resting protein levels of soluble VEGF receptor-1 in interstitial fluid, and of VEGF, thrombospondin-1 (TSP-1) and tissue inhibitor of matrix metalloproteinase-1 (TIMP1) in muscle were unaffected by training, whereas endothelial nitric oxide synthase protein levels in muscle increased by 50% (P < 0.05). Before and after training, acute exercise induced a similar increase (P < 0.05) in the mRNA level of angiopoietin 2, matrix metalloproteinase 9 and TSP-1. After training, TIMP1 mRNA content increased with exercise (P < 0.05).

Conclusions: Acute exercise induced a similar increase in the gene-expression of both pro- and anti-angiogenic factors in untrained and trained muscle. We propose that the increase in anti-angiogenic factors with exercise is important for modulation of angiogenesis. The lack of effect of training on basal muscle VEGF protein levels and VEGF secretion during exercise suggests that increased VEGF levels are not a prerequisite for exercise-induced capillary growth in healthy muscle.

Hoier B, Passos M, Bangsbo J, Hellsten Y. Intense intermittent exercise provides weak stimulus for VEGF secretion and capillary growth in skeletal muscle. Exp Physiol. 2012 Sep 7. [Epub ahead of print]

University of Copenhagen, Copenhagen, Denmark;
The effect of acute intense intermittent exercise compared to moderate intensity exercise, on angiogenic factors and the effect of four weeks of intense intermittent training on capillary growth were examined in nine young healthy males, pre-conditioned by moderate intensity endurance training. The intense training consisted of 24 one-min cycling bouts at an initial work rate of 316 ± 19W (~117% of pre VO2 max), performed 3 times/week. Skeletal muscle biopsies and muscle microdialysates were otained from m.v. lateralis before, during, and after acute exercise performed at either moderate or high intensity. Comparison of the response in angiogenic factors to acute moderate versus high intensity exercise, performed prior to the intense training intervention, revealed that intense exercise resulted in a markedly lower (~60%; P < 0.05) increase in interstitial VEGF than did moderate intensity exercise. Muscle interstitial fluid obtained during moderate intensity exercise increased endothelial cell proliferation in vitro more than interstitial fluid obtained during intense exercise (6-fold vs. 2.5-fold, respectively; P < 0.05). The four weeks of high intensity training did not lead to an increased capillarization in the muscle but abolished the exercise induced increase in mRNA for several angiogenic factors, increased the eNOS protein levels, lowered TSP-1 protein levels in muscle but increased interstitial TSP-1 protein levels.
Conclusions: Intense intermittent exercise provides a weak stimulus for VEGF secretion and endothelial cell proliferation and that intense intermittent training does not induce a sufficient angiogenic stimulus to induce capillary growth in muscle previously conditioned by moderate intensity exercise.

Gunnarsson TP, Christensen PM, Holse K, Christiansen D, Bangsbo J. Effect of additional speed endurance training on performance and muscle adaptations. Med Sci Sports Exerc. 2012 Oct;44(10):1942-8.
Department of Exercise and Sport Sciences, Section of Human Physiology, University of Copenhagen, DENMARK.
The present study examined the effect of additional speed endurance training (SET) during the season on muscle adaptations and performance of trained soccer players. Eighteen sub-elite soccer players performed one session with six to nine 30-s intervals at an intensity of 90%-95% of maximal intensity (SET) a week for 5 wk (SET intervention). Before and after the SET intervention, the players carried out the Yo-Yo intermittent recovery level 2 (Yo-Yo IR2) test, a sprint test (10 and 30 m), and an agility test. In addition, seven of the players had a resting muscle biopsy specimen taken and they carried out a running protocol on a motorized treadmill before and after the SET intervention. After the SET intervention, the Yo-Yo IR2 test (n = 13) performance was 11% better (P < 0.05), whereas sprint (n = 15) and agility (n = 13) performances were unchanged. The expression of the monocarboxylate transporter 1 (n = 6) was 9% higher (P < 0.05). and the expression of the Na/K pump subunit β1 (n = 6) was 13% lower (P < 0.05) after the SET intervention. The Na/K pump subunits α1, α2, as well as the monocarboxylate transporter 4 and the Na/H exchanger 1 (n = 6) were unchanged. After the SET intervention, the relative number of Type IIx fibers and oxygen consumption at 10 km·h were lower (P < 0.05), whereas V˙O2max was unchanged.
Conclusions:  Adding 30 min of SET once a week during the season for trained soccer players did lead to an improved ability to perform repeated high-intensity exercise, with a concomitant increase in the expression of monocarboxylate transporter 1 and an improved running economy.

Scott BR, Lockie RG, Knight TJ, Clark AC, Janse de Jonge X AK. A Comparison of Methods to Quantify the In-Season Training Load of Professional Soccer Players. Int J Sports Physiol Perform. 2012 Sep 5. [Epub ahead of print]
Exercise and Sport Science, Faculty of Science and Information Technology, University of Newcastle, Ourimbah, New South Wales, Australia.
The aim of the study was to compare various measures of training load (TL), derived from physiological (heart rate [HR]), perceptual (rating of perceived exertion [RPE]) and physical (global positioning system [GPS] and accelerometer) data, during in-season field-based training for professional soccer. Fifteen professional male soccer players (age: 24.9 ± 5.4 yr, body mass: 77.6 ± 7.5 kg, height: 181.1 ± 6.9 cm) were assessed in-season, across 97 individual training sessions. Measures of external-TL (total distance [TD], the volume of low-speed activity [LSA; <14.4km·h-1], high-speed running [HSR; >14.4 km·h-1] and very high-speed running [VHSR; >19.8 km·h-1], and Player Load™), HR and session-RPE (sRPE) scores were recorded. Internal-TL scores (HR-based and sRPE-based) were calculated, and their relationships with measures of external-TL were quantified using Pearson's product moment correlations. Physical measures of TD, LSA volume and Player Load™ provided large, significant (r = 0.71-0.84; P < 0.01) correlations with the HR-based and sRPE-based methods. Volume of HSR and VHSR provided moderate to large, significant (r = 0.40-0.67; P < 0.01) correlations with measures of internal-TL.
Conclusions:  Whilst the volume of HSR and VHSR provided significant relationships with internal-TL, physical performance measures of TD, LSA volume and Player Load™ appear to be more acceptable indicators of external-TL, due to the greater magnitude of their correlations with measures of internal-TL.

Bradley PS, Bendiksen M, Dellal A, Mohr M, Wilkie A, Datson N, Orntoft C, Zebis M, Gomez-Diaz A, Bangsbo J, Krustrup P. The Application of the Yo-Yo Intermittent Endurance Level 2 Test to Elite Female Soccer Populations. Scand J Med Sci Sports. 2012 Jun 19. doi: 10.1111/j.1600-0838.2012.01483.x. [Epub ahead of print]

Department of Sport and Exercise, University of Sunderland, Sunderland, UK.
The aim of this study was to evaluate the application of the Yo-Yo intermittent endurance test level 2 (Yo-Yo IE2) to elite female soccer populations. Elite senior (n = 92), youth (n = 42), domestic (n = 46) and sub-elite female soccer players (n = 19) carried out the Yo-Yo IE2 test on numerous occasions across the season. Test-retest coefficient of variation (CV) in Yo-Yo IE2 test performance in domestic female players was 4.5%. Elite senior female players' Yo-Yo IE2 test performances were better (P < 0.01) than elite youth, domestic and sub-elite players (mean ± standard deviation; 1774 ± 532 vs 1490 ± 447, 1261 ± 449, and 994 ± 373 m). For elite senior female players, wide midfielders (2057 ± 550 m) had a higher Yo-Yo IE2 test performance (P < 0.05) than central defenders (1588 ± 534 m) and attackers (1516 ± 401 m), but not central midfielders (1764 ± 473 m) or full-backs (1964 ± 522 m). Large correlations were observed between Yo-Yo IE2 test performance and the total and high-intensity distance covered (r = 0.55; P < 0.05) during elite senior soccer matches (r = 0.70; P < 0.01). A large correlation was also obtained between Yo-Yo IE2 test performance and (r = 0.68; P < 0.01). Performances in the Yo-Yo IE2 test were greater (P < 0.05) in the middle and the end of the season compared with the preparation period for elite youth female players (1767 ± 539 and 1742 ± 503 vs 1564 ± 504 m) and in elite senior female players, Yo-Yo IE2 test performance increased by 14% (P < 0.01) after completing 4 weeks of intense training prior to the FIFA Women's World Cup Finals (2049 ± 283 vs 1803 ± 342 m).
Conclusions: The Yo-Yo IE2 test is reproducible and is an indicator of the match-specific physical capacity of female soccer players. Furthermore, the Yo-Yo IE2 test illustrates sensitivity by differentiating intermittent exercise performance of female players in various competitive levels, stages of the season and playing positions.

Hulton AT, Edwards JP, Gregson W, Maclaren D, Doran DA. Effect of Fat and CHO Meals on Intermittent Exercise in Soccer Players. Int J Sports Med. 2012 Sep 12. [Epub ahead of print]
Research Institute for Sport & Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
Pre-exercise meals containing carbohydrates (CHO) are recommended to athletes, although there is evidence to suggest that a high fat meal prior to exercise increases utilisation of fats yet may not adversely affect performance. This study investigated the effect of a high fat and high CHO pre-exercise meal prior to high intensity intermittent exercise. Ten male recreational soccer players performed a soccer specific protocol followed by a 1 km time trial 3 ½ h after ingesting one of 2 test meals, high fat meal (HFM) or a high CHO meal (HCM). Blood glucose, fatty acids (FA), glycerol, β-hydroxybutyrate, lactate and insulin were assessed prior to the meal, pre-exercise, half-time, and post-exercise, whilst rates of CHO and fat oxidation were determined at 4 time points during the exercise as well as heart rate (HR) and rating of perceived exertion (RPE). Significant increases in FA, glycerol, β-hydroxybutyrate and fat oxidation after the HFM were observed, while CHO oxidation was significantly higher following the HCM (P<0.05). No performance effect was found for the 1 km time trial (HFM: 228.6+14.4 s; HCM: 229.4+26.5 s) (mean+SD).
Conclusions: The type of meal ingested prior to soccer simulated exercise has an impact on metabolism, but not on the subsequent performance.