Wednesday, June 29, 2011


These days most of us get ready for the new season. Here are some tests for football players’ pre-season testing. The criteria for their inclusion in the list are 1) specificity to football, 2) validity, reliability, 3) they are easy to conduct in terms of time and resources.

Body composition, growth  
-Body fat (skinfolds)
Skinfold caliper, scales, tape
length asymmetries
-Legs length

Sit & reach
Specific device or ruler
Reaction time
Photocells or stopwatch
Counter-movement jump
Contact mat or force plate

Squat jump

Drop jumps

505 test
Photocells or stopwatch

Illinois test
Photocells or stopwatch

Ajax shuttle test
Photocells or stopwatch
Anaerobic power
Repetitive jumps test
Contact mat or force plate
Anaerobic lactic acid capacity
-7reps of 35m with 25sec of active recovery
-10 reps X 20m

Photocells or stopwatch
Aerobic capacity
-20m endurance shuttle run
-Yo-Yo intermittent recovery test
CD player
Leg muscle strength asymmetries
Countermovement jump
Force plate
Maturity indices (for young players)
-hand and wrist X-ray

Monday, June 27, 2011


Repeated sprints training is a very popular one, especially in football. Coaches use different combinations, like 5 to 10 repetitions of 20-40m with 10-25 sec of active, passive or free recovery. What is the appropriate number of repetitions?

In the literature, a very large variability in fatigue induced with this kind of training exists. Fatigue indices range from 6-27% in different studies as well as for relatively similar level players within the same study. This means that training with a standard number of repetitions results in different fatigue level among players and thus different adaptations.

  1. Test players with the same protocol as training (10-15x30m with 25sec active recovery)
  2. Calculate fatigue index [FI= (worst time-best time/best time) * 100] for sprints 1-7, 1-10, 1-15
  3. Create an equation for FI with number of sprints for each player
  4. Decide the FI level you want to work for this period (6-10% is a good one)
  5. Estimate the number of sprints for each player

Saturday, June 25, 2011

MRI brain scan of a cyclist while exercising

The first study on brain activity during exercise up to VO2max is a reality. The study has been conducted at the Medical Research Council/UCT Research Unit for Exercise Science and Sports Medicine, University of Cape Town, South Africa.

Please watch the video

Thursday, June 23, 2011

Say it in a different way: the power of words

Today, I am posting this link to emphasize the importance of communication. Good, clear way of communication can improve our lives.

No more words!

I hope you enjoy the video.

Wednesday, June 22, 2011

Do strength asymmetries increase the risk for muscle injury?

Today, I am going to discuss the findings of a study published in this month’s issue of the British Journal of Sports Medicine (Fousekis et al., 2011). Muscle strength, flexibility, proprioception, anthropometry and knee stability were evaluated pre-season in 100 football players. The history of previous injuries was also recorded and players were followed for 10 months for injuries occurrence. Asymmetries were defined according to standard criteria. The main findings were
  •      Players with eccentric hamstring strength asymmetries and functional leg length asymmetries presented a higher risk for a hamstring muscle strain during the season.
  •         Previous injury did not affect hamstring injury occurrence.
  •          Players with high body mass, with eccentric strength and flexibility asymmetries presented a higher risk for quadriceps muscle strain.

The new thing with this study is that it examines most of the intrinsic risk factors at the same time. However, there are also some points to consider before applying these findings to other players
  • Sample size was small for this kind of research
  • Participants were not of high level and this limits the findings’ generalization.

To my opinion, however, the key messages from this study are
  1. To evaluate the risk of muscle injury in a player we must consider as many factors as possible at the same time
  2. Muscle strength and in particular eccentric strength seems to be related with hamstring and quadriceps muscle strain, at least in non-elite players. The question of whether it is the same in elite level players remains to be answered.

Fousekis et al. Br J Sports Med 45(9):709-714, 2011.

Tuesday, June 21, 2011

Training periodization: Is it applicable to football?

We are now at the stage that everybody is thinking and planning on the new season. Phases, targets, plans and more. Can we adopt a periodization model in football?

To my opinion, this is extremely difficult at the elite level. At this level, there is a 5-7 weeks preparation period before the official matches start, followed by a period of almost 4 months in which the team usually plays 2 matches per week. So, how can we plan periodization? In young players, I think that periodization must be the case. At these ages, players’ development must be the main target and not team performance and win on weekend match.

There are mainly 2 approaches in training periodization
  1. The traditional training planning: According to this many different aspects of physical, technical and tactical attributes are all the target of a certain period. It is a rather “mixed” model which might cause some “conflicts” and overload the players.
  2. The block periodization: this is the modern approach in which planning includes the consecutive development, at certain “blocks”, of each ability. The advantage of this model is clarity of objective, flexibility and variety of activities at each block. Another important aspect is that training intensity can remain high since it is concentrated at the improvement of a single factor each time.

Which approach is your favorite one? Please feel free to comment.


Are hyperthermia and dehydration causes of fatigue in football? Yes, they are when match or training is performed in a warm environment.

WHAT IS A WARM ENVIRONMENT? It is the combination of dry temperature and relative humidity that cause thermal stress to the human body. Generally, a warm environment is defined at a temperature higher than 28 oC with moderate relative humidity. At this environment, fatigue arrives before muscle glycogen and blood glucose are lowered below a critical level.

WHAT IS THE MECHANISM OF FATIGUE IN SUCH ENVIRONMENT? Players sweat a lot for thermoregulation. This results in body fluids loss and, if not replaced, to dehydration. Dehydration and thermal stress due to the warm environment result in inside body temperature elevation. When body’s core temperature becomes higher than 38.5 oC in non-elite and higher than 39 oC in elite players, physical and mental performance decline. Indeed, studies in football players show that both distance covered and skill performance decline with hyperthermia and dehydration.

Studies with brain scanning techniques show that hyperthermia negatively affects blood supply and function of certain areas of the brain that are associated with motor unit recruitment and decision-making. Based on this indirect evidence, it is reasonable to speculate that hyperthermia might affect technical and tactical decisions during the match in football players.

  1. Avoid training during the warm hours of day.
  2. Adopt pre-cooling strategies before training/match and in half time. In the literature, several strategies are proposed like cold water immersion, ice placement on the legs, cooling vests.
  3. Drink as much fluid as you can before and during training/matches. Fluid taken should not exceed losses due to sweating. Fluids should be isotonic with a low carbohydrate concentration (2-5%). Water drinking is also effective in minimizing dehydration and hyperthermia.
  4. Acclimatization to heat will alleviate the symptoms in 3-10 days.
  5. Response to playing and training in the heat is different from player to player.

For more reading
Grantham et al. Scand J Med Sci Sports Suppl 3: 161-167, 2010
McGregor et al. J Sports Sci 17:895-903, 1999
Nassis & Geladas. Eur J Appl Physiol 88:227-233, 2002

Sunday, June 19, 2011


To answer the title question one needs to measure a physical parameter, let say aerobic fitness, and match performance for the same players in a period of 7-10 days. Match performance can be evaluated either with the performance analysis systems or with GPS devices. Multi-camera systems are more expensive whereas GPS are more available.

Aerobic fitness is usually evaluated in the lab or in the field. The most popular tests in the field are: Yo-Yo intermittent recovery, multistage shuttle run and the Hoff test. In the first two, aerobic fitness is evaluated with repeated 20-m shuttle runs whereas in the latter, the player runs in a larger space with the ball.

The association between these tests and the match performance in elite young players is shown below. The main conclusions are
  • Yo-Yo intermittent recovery run 1 (IR1) and multistage shuttle run test (MSRT) are both associated with distance covered at high intensity during the game
  • Distance covered in the multistage shuttle run test is positively related with total distance covered during the match
  • Hoff test IS NOT associated with total distance and distance covered at high intensity during the match

Table. Association between different tests and match performance.
Match activity
Yo-Yo IR1
Total distance
Very weak
Very weak
High intensity distance
Very weak
 Source: Castagna et al., 2010.

Both Yo-Yo intermittent run 1 and multistage shuttle run tests can be used for the evaluation of aerobic fitness in young players.

For more reading
Castagna et al. J Strength & Cond Res 24:3227-3233, 2010
Nassis et al. J Strength & Cond Res 24:2693-2697, 2010

Wednesday, June 15, 2011


Looking at the data from the 2 studies on elite players mentioned in my articles this week, it is worth noting that there is a large variation in the size of improvement after training.

Let me remind you that in the study with the elite champions league players (probably from FC Barcelona) aerobic fitness, strength and explosiveness were evaluated after the 8-week pre-season training period (Helgerud et al., 2011). Maximal oxygen uptake improved by 8.6% whereas half-squat maximal strength by 51.7%. If one looks more closely to the data
  • Maximal oxygen uptake improved by 3-5% in 3 players and 15% in 1 player. Interestingly, the player with 15% improvement had already a high initial value (64 ml/kg/min)
  • In maximal strength test, there were players that improved by only 10% and 1 player that improved by 2.5-fold.

In the study with elite players from Italian Serie A (Castagna et al., 2011) time devoted in high intensity training ranged from 120-205 min per week. However, improvements in aerobic fitness ranged from 0 (!) to almost 20%. Another observation: for the same time spend at high intensity training (160 min) 1 player improved by 4%, 1 players improved by 7%, another 1 by 9% and the last one presented NO IMPROVEMENT AT ALL!

It seems, therefore, that
  1. Players respond differently with the same training load
  2. This happens even at the elite level

The explanation for these results is not clear. Age, initial fitness level and genes (and other, not discovered yet factors) may interact to affect training adaptations.

Whatever the reason, these results highlight the importance of the individualized programs to improve certain aspects of fitness.


Today, I would like to share with you my thoughts on the OPTIMAL training intensity for aerobic fitness improvement in elite players? What is the range of intensities needed in the pre-season period? How much time should we spend at high intensity?

These questions were set by Castagna and colleagues (2011) who recorded the 6-week pre-season training of the 1st team squad of PALERMO football club. The players came back to training after a post-championship period of 4 weeks. Last season the team had finished 5th in the Italian premier league (Serie A).

Following pre-start testing in the lab, these elite level players followed their typical training program to develop fitness, technical and tactical aspects of game. In general, they
  • Performed aerobic training sessions using ball drills
  • Did circuit training at 80-90% 1RM for strength improvement
  • Performed 10-30m sprints (2 times per week)

The ratio between the time spend in anaerobic and aerobic training was 1:10.

The main findings with practical applications were
  1. Improvement in aerobic fitness was associated with time spend at high-intensity only (Heart rate >90% of max)
  2. It seems, based on these results, that in elite level players high-intensity training should account for at LEAST 8% OF TOTAL WEEKLY TRAINING TIME

These results emphasize the role of high-intensity training in improving physical aspects of match play at elite football players.

Monday, June 13, 2011


This is an interesting question for coaches and sport scientists. Although there some data in the literature, they mostly refer to moderate level players. In the study by Helgerund et al. (2011) 21 elite players, all from a successful team in the Champions League, performed strength training for maximal strength improvement 2 times per week for the pre-season 8-week period. They did 4 sets at loads equal to 4 maximal repetitions of half-squat with emphasis on the concentric action. No specific sprint training was performed apart from drills in small sided games. Similarly, no jump training was executed. Training hours and relative intensities in a week were
  • Stretching, 1.5 hr
  • Endurance training (without ball) 1.5 h (90-95% max heart rate)
  • Small sided games, 2.5 hr (85-90% heart rate max)
  • Technical training, 2 hr
  • Strength training, 1 hr
  • Match play, 1.5 hr (85-90% heart rate max)

After 8 weeks, countermovement jump (CMJ) was improved by 5.2% (from 57.2 to 60.2 cm) and 10m run by 3.2 % (from 1.87 to 1.81 sec). Although, absolute changes might make the difference at elite level, we can notice that
  • This is an improvement worth noting given that players were elite level
  • Improvements in half-squat maximal strength were associated with improvement in legs’ explosiveness
  • A big improvement in max strength (52%) resulted only in a small improvement in CMJ and 10m run. This highlights the need for more specific exercises to transfer gains in strength from the gym into the match activities.

Friday, June 10, 2011


Strength and endurance are important components of physical fitness. Classic knowledge suggests that simultaneous training for strength and endurance will diminish adaptations. However, these studies have been in normal, healthy subjects and not elite athletes. Besides that the reality is that both training modes are usually incorporated in the modern training programs. What is the truth?

Another issue is related on the effect of training without ball on physical performance in elite players. There is always the question on how we can improve physical fitness in a short, limited time. What is the most effective method in elite football players?

A nice study was published few days ago that addressed these questions in elite football players (Helgerud et al., 2011). One of the co-author was Dr Rodas from Barcelona FC Medical department. In this study, elite Champion League players performed strength training (4x4 reps maximum, only half-squat) and endurance training (4X4min running at 90-95% of maximal heart rate). Training was performed twice a week in the mornings over the 8-weeks pre-season period. As you realize no control group was included in this study due to its nature.

The results showed almost 9% increase in maximal oxygen uptake (from 60.5 to 67 ml/kg/min). Maximal strength, in half-squat, increased 52% following training. 

Wednesday, June 8, 2011


The answer to the first question comes from the recent study by Ekstrand et al (2011) which has showed that muscle injuries incidence increases with age. In this study, professional players were placed in 3 age categories (16-21 yrs, 22-30 yrs & >30 yrs). The analysis showed 35% greater incidence for muscle injury in training in players aged below 22 years old compared with aged >30 years old. No difference was observed between the intermediate groups. During a match, young players had a significantly lower incidence compared with the other 2 categories. These results suggest that the incidence of muscle injury increases with age in professional players.

The next question is: is this associated with a delayed recovery rate with age? There is a limited number of studies on this issue and these are not in football players but athletes in extreme sports (mountain running). One study has shown that recovery rate is slower with age (Easthope et al., 2010). In another study, recovery rate was similar in young and non-young runners after a long race (Nassis et al., unpublished data). In the latter study, athletes in the 2 age-groups had similar training history and thus any difference could be attributed to the biological process of recovery. It seems, therefore, that recovery rate might not be different with age when athletes are of similar training level. More data are needed specific on football players.

Easthope et al. European Journal of Applied Physiology 110: 1107-1116, 2010.
Ekstrand et al. American Journal of Sports Medicine, 39 (6): 1226-32, 2011.
Nassis et al. under review

Tuesday, June 7, 2011


A comparison of the match related injury incidence when playing on artificial turf versus natural grass was performed by Ekstrand and colleagues (2011) in professional football players. Their results showed a lower incidence of muscle injuries when playing on new-generation artificial turf (artificial turf: 6.1; natural grass: 9.58 injuries/1000hours of total exposure).

Ekstrand et al. American Journal of Sports Medicine, 39 (6): 1226-32, 2011.

Monday, June 6, 2011


This is one of the major findings of the study published in the American Journal of Sports Medicine this month by Ekstrand and colleagues. 52 football teams [best 24 European Clubs (UCL), 15 teams from the Swedish first League and another 15 European teams] were followed during the period 2001-9. The main findings were:
  • Muscle injuries constituted 31% of all injuries.
  • 92% of all muscle injuries affected the lower extremities; hamstrings (37%), adductors (23%), quadriceps (19%) and calf muscles (13%).
  • 16% of the muscle injuries were reinjuries. Rate was lower in the UCL teams (13%) and higher in the Swedish league teams. This was attributed, at least in part, to the greater medical and physio support in UCL teams.
  • Reinjuries caused 30% longer absences than first-time injuries (average: 17.8 vs 13.8 days, respectively).
  • As in previous studies, muscle injuries tended to occur more frequently in the last quarter of each half.
  • The incidence of all muscle injuries increased with age (age groups: 16-21 yrs, 22-30 yrs & >30 yrs).
  • The incidence of calf strains during the match increased with age. There was no difference between age groups in the incidence of hamstrings, quadriceps and adductors.
These results may help in designing more effective injury prevention programs and improve injury rehabilitation.

Ekstrand et al. American Journal of Sports Medicine, 39 (6): 1226-32, 2011.


Recently, I have read a nice study from the US Navy which examined blood protein biomarkers that distinguish superior performers under psychological stress. This is an innovative approach that I think might have applications for elite players’ selection in the near future.

As I said before the study was conducted by Naval Aerospace Research Laboratory in collaboration with the Mississippi State University and Indiana University of Pennsylvania and was supported by a grant from USDA. The rationale behind the study was to identify biomarkers of performance under stress in an effort to improve selection of the SUPERIOR PERFORMERS to naval aviation. This would save the navy millions of dollars since late stage navy aviator training failures are estimated to cost >1,000,000 dollars, according to the authors of the paper.

The researchers evaluated blood using high-throughput proteomics to get biomarkers. Following this stage, they used a very sophisticated mathematical approach (Ingenuity Pathways Analysis) to identify physiological processes related to performance under stress. They found 175 differentially expressed proteins concentrated in two physiological processes. They concluded that blood protein biomarkers are promising complementary tests to select superior performers under stress.

In elite football we search also for superior performers under high psychological stress. No doubt that this is the start of the story. Looking at the data of the paper I must say that there are still some points that need further clarification regarding the experimental design and the methodology. In addition, a mechanism that explains the link between the protein biomarkers and from these the modeled physiological processes with physical performance need to be established.

 However, I must say that there is no perfect study. What this study presents is an novel, complementary approach to improve superior performers' selection. This makes these results of great value to other fields as well. I can speculate that, in the near future, we might be in a position to effectively select the best players by using also certain biomarkers in the blood or, who knows, in saliva.

Cooksey et al. Identifying blood biomarkers and physiological processes that distinguish humans with superior performance under psychological stress. PLoS One 2009 18;4(12); e8371

Thursday, June 2, 2011


On June 1st,  a nice paper was published by Dvorak and colleagues (2011) describing the incidence of injuries in the 2010 FIFA world cup. Major findings are
  • 2 injuries per match. 65% of them were due to contact with another player.
  • Injury rate increased with match time being almost 5-times higher at 76-90 min compared with 1-15 min of the match.
  • Half of the injuries resulted in absence from sport of 1-3 days, 8% in absence of 4-7 days and 2.7% resulted in absence of 10 days.
  • 104 injuries occurred during training (7.9 per 1000 player hours). Most of them were classified as overuse.
  • The most frequent diagnosis, for both match and training injuries, was contusion of thigh and lower leg and thigh strain.
  • Match injuries incidence was lower compared with previous world cups since 1998 (1998: 2.4, 2002: 2.7, 2006: 2.3 & 2010: 2 injuries per match).
Dvorak et al. British Journal of Sports Medicine 45:626-630, 2011.