Monday, November 11, 2013

Training loads and injuries (FREE downloads)

Gabbett TJ. Reductions in pre-season training loads reduce training injury rates in rugby league players. Br J Sports Med. 2004 Dec;38(6):743-9.

Johnson A, Doherty PJ, Freemont A. Investigation of growth, development, and factors associated with injury in elite schoolboy footballers: prospective study. BMJ. 2009, 338: b490

Saturday, November 9, 2013

What's new on small-sided games?

A number of interesting papers have been published on small-sided games. Without ignoring the importance of each one of them, I would like to focus more on the paper published by Fradua and colleagues in the Journal of Sports Sciences (Fradua et al., 2013).

The aim of the study was to examine, among others, the individual playing area and length and width of the rectangles during professional football (soccer) matches.

Matches from 5 different 1st Spanish division teams were analysed and the main findings were:
  • The individual playing area ranged from 79 to 94 m2.
  • Rectangle length and width varied at different playing zones (1-6; zone 1 was the zone nearest the goal of the team in possession of the ball & zone 6 was the one nearest the opponent's goal).

Practical implications
  • Pitch sizes should vary and range between 80 (zone 3 & 4) and 90 m2 (zones 1, 2, 5 & 6)
  • Length to width ratio should also be adjusted to 1:1 (zones 1, 2, 5 & 6) and 1:1.3 (zone 3 & 4)

Fradua, Zubillaga, Caro, Fernandez-Garcia, Ruiz-Ruiz, Tenga (2013). Designing small-sided games for training practical aspects in soccer: extrapolating pitch sizes from full-size professional matches. J Sports Sci 31(6): 573-581

Thursday, November 7, 2013

What's new in sport science?

Training and game loads and injury risk in elite Australian footballers

Rogalski B, Dawson B, Heasman J, Gabbett T (2013). J Sci Med Sport  16(6): 499-503

Tohe aim was to examine the relationship between combined training and game loads and injury risk in elite Australian footballers. Prospective cohort study. Forty-six elite Australian footballers (mean±SD age of 22.2±2.9 y) from one club were involved in a one-season study. Training and game loads (session-RPE multiplied by duration in min) and injuries were recorded each time an athlete exerted an exercise load. Rolling weekly sums and week-to-week changes in load were then modelled against injury data using a logistic regression model. Odds ratios (OR) were reported against a reference group of the lowest training load range. Larger 1 weekly (>1750AU, OR=2.44–3.38), 2 weekly (>4000AU, OR=4.74) and previous to current week changes in load (>1250AU, OR=2.58) significantly related (p<0.05) to a larger injury risk throughout the in-season phase. Players with 2–3 and 4–6 years of experience had a significantly lower injury risk compared to 7+ years players (OR=0.22, OR=0.28) when the previous to current week change in load was more than 1000AU. No significant relationships were found between all derived load values and injury risk during the pre-season phase. In-season, as the amount of 1–2 weekly load or previous to current week increment in load increases, so does the risk of injury in elite Australian footballers. To reduce the risk of injury, derived training and game load values of weekly loads and previous week-to-week load changes should be individually monitored in elite Australian footballers.

The physiological response, time-motion characteristics and reproducibility of various speed endurance drills in elite youth soccer players: small sided games vs generic running.
Ade, Harley, Bradley (2013). Br J Sports Med 47(17): v-e4     
The aim of the study was to quantify the physiological responses, time-motion characteristics and reproducibility of various speed endurance production (SEP) and speed endurance maintenance (SEM) drills. Twenty-one elite male youth soccer players completed four drills: (1) SEP 1 v 1 small sided game, (2) SEP running drill, (3) SEM 2 v 2 small sided game and (4) SEM running drill. The SEP drills consisted of eight bouts of 30 s with 120 s recovery (1:4 exercise to rest ratio) whilst SEM drills encompassed eight bouts of 60 s with 60 s recovery (1:1 exercise to rest ratio). Heart rate response, blood lactate concentration, rating of perceived exertion and time-motion characteristics were recorded for each drill. The SEP and SEM running drills elicited greater (P<0.05) heart rate responses, blood lactate concentrations and subjective ratings of perceived exertion than the equivalent small sided games (ES: 1.1-1.4 & 1.0-3.2). Players covered less (P<0.01) total distance, high-, very high-speed running and sprint distance in the SEP and SEM small sided game's compared to the equivalent running drills (ES: 6.0-22.1 & 3.0-18.4). Greater distances (P<0.01) were covered in high and maximum acceleration/deceleration bands during the SEP and SEM small sided game's compared to the equivalent running drills (ES: 2.6-4.6 and 2.3-4.8). Small-moderate test-retest variability was observed for heart rate response (CV: 0.9-1.9%), ratings of perceived exertion (CV: 2.9-5.7%) and blood lactate concentration (CV: 9.9-14.4%); Moderate-large test-retest variability was observed for high-intensity running parameters (CV: >11.3%) and the majority of acceleration/deceleration distances (CV: >9.8%) for all small sided games and running drills. The data demonstrate the differential response of SEP and SEM training for taxing various energy systems and the superior acceleration/deceleration profiles of small sided games compared to generic running drills.

Effects of small-sided game and change-of-direction training on reactive agility and change-of-direction speed.

Young, Rogers (2013). J Sports Sci Sep 9 [Epub ahead of print]

The purpose of this study was to determine the effects of training change-of-direction speed and small-sided games on performance in the Planned-AFL agility test and reactive agility. Twenty-five elite-standard U-18 Australian Rules football players were randomly allocated either to a change-of-direction group or a small-sided games group. Players participated in one or two 15-min sessions per week with 11 sessions conducted over a 7-week period during the season. Tests conducted immediately before and after the training period included the Planned-AFL agility test and a video-based reactive agility test specific to Australian Rules football. The reactive agility test variables were total time, decision time and movement response time. The small-sided games group improved total time (P = 0.008, effect size = 0.93), which was entirely attributable to a very large reduction in decision time (P < 0.001, effect size = 2.32). Small-sided games produced a trivial change in movement response time as well as in the Planned-AFL agility test (P > 0.05). The change-of-direction training produced small to trivial changes in all of the test variables (P > 0.05, effect size = 0-0.2). The results suggest that small-sided games improve agility performance by enhancing the speed of decision-making rather than movement speed. The change-of-direction training was not effective for developing either change-of-direction speed as measured by the Planned-AFL test or reactive agility.

Preconditioning strategies to enhance physical performance on the day of competition.

Kilduff, Finn, Baker, Cook, West (2013). Int J Sports Physiol Perform 8(6): 677-681

Sports scientists and strength and conditioning professionals spend the majority of the competition season trying to ensure that their athletes' training and recovery strategies are appropriate to ensure optimal performance on competition day. However, there is an additional window on the day of competition where performance can be acutely enhanced with a number of preconditioning strategies. These strategies include appropriately designed warm-up, passive heat maintenance, postactivation potentiation, remote ischemic preconditioning, and, more recently, prior exercise and hormonal priming. The aim of this review was to explore the potential practical use of these strategies and propose a theoretical timeline outlining how they may be incorporated into athlete's precompetition routine to enhance performance. For the purpose of this review the discussion is confined to strategies that may enhance performance of short-duration, high-intensity sports (eg, sprinting, jumping, throwing).

Tendon and skeletal muscle matrix gene expression and functional responses to immobilisation and rehabilitation in young males: Effect of growth hormone administration. J Physiol Nov 2013  

Boesen, Dideriksen, Couppé, Magnusson, Schjerling, Boesen, Kjaer, Langberg. J Physiol Nov 2013 [Epub ahead of print]

We examined the effect of growth hormone (GH) on connective tissue of tendon and skeletal muscle during immobilisation and re-training in humans. Young men (20-30 years; n=20) were randomly assigned to daily recombinant GH (rhGH)(33-50μg/kg/d) or placebo (Plc), and had one leg immobilised for two weeks followed by six weeks of strength training. Cross sectional area (CSA), maximal muscle strength (MVC) and biomechanical properties of m.quadriceps and patellar tendon were determined. Muscle and tendon biopsies were analysed for mRNA of collagen (COL-1A1/3A1), insulin-like growth factors (IGF-1Ea/Ec), lysyloxidase (LOX), matrix metalloproteases (MMP-2 and -9), decorin and tenascin-C. Fibril morphology was analysed by transmission electron microscope (TEM) to detect changes in fibril diameter distribution. In muscle the CSA and MVC declined with immobilisation, and recovered with rehabilitation similar in both groups. Likewise, both groups increased in IGF-1Ea/Ec and COL-1A1/3A1 expression in muscle during re-training after immobilisation compared to baseline, and the rise was more pronounced when subjects recieved GH. The tendon CSA did not change during immobilisation, but increased in both groups during six weeks of rehabilitation (~14%). A decline in tendon stiffness after immobilisation was observed only in Plc, and an increase during six weeks rehabilitation was observed only in GH. IGF-1Ea and COL-1A1/3A1 mRNA increased with immobilisation in the GH group only, and LOX mRNA was after immobilisation higher in the GH group vs Plc. Both groups increased in MMP-2 with immobilisation, whereas no changes in MMP-9, decorin and tenascin-C were observed. Tendon fibril diameter distribution remained unchanged in both groups. In conclusion, GH stimulates collagen expression in both skeletal muscle and tendon and abolishes the normal inactivity related decline in tendon stiffness and LOX, and results in an increased tendon CSA and stiffness during rehabilitation. GH has a matrix stabilising effect during periods with inactivity and rehabilitation in humans.

Sources: PubMed & the journals

Monday, November 4, 2013

Hot topics in Sport Science (Free downloads)

Muscular and systemic correlates of resistance training-induced muscle hypertrophy by Mitchell et al., PLoS One. 2013 Oct 9;8(10):e78636

VO2max Trainability and High Intensity Interval Training in Humans: A Meta-Analysis by Bacon et al., PLoS One. 2013 Sep 16;8(9):e73182