Friday, February 22, 2013

Sports Science in Elite Football: what's new? PART 2
Dellal et al (2013). The effects of a congested fixture period on physical performance, technical activity and injury rate during matches in a professional soccer team. Br J Sports Med Febr 19 [Epub ahead of print] 

In modern professional soccer, the ability to recover from official match-play and intense training is often considered a determining factor in subsequent performance. To investigate the influence of playing multiple games with a short recovery time between matches on physical activity, technical performance and injury rates. The variation of physical (overall distance, light-intensity, low-intensity, moderate-intensity and high-intensity running) and technical performance (successful passes, balls lost, number of touches per possession and duels won) of 16 international players was examined during three different congested periods of matches (six games in 18 days) from the French League and Cup (n=12), and the UEFA Champions' League (n=6) during the 2011-2012 season and compared with that reported in matches outside these periods. Data were collected using a computerised match analysis system (Amisco). Injury rate, time loss injuries, as well as the mechanism, circumstances and severity of the injury were also analysed. No differences were found across the six successive games in the congested period, and between no congested and the three congested periods for all the physical and technical activities. The total incidence of injury (matches and training) across the prolonged congested periods did not differ significantly to that reported in the non-congested periods. However, the injury rate during match-play was significantly higher during the congested period compared with the non-congested period (p<0.001). The injury rate during training time was significantly lower during the congested period compared with the non-congested periods (p<0.001). The mean lay-off duration for injuries was shorter during the congested periods compared with the non-congested periods (9.5±8.8 days vs 17.5±29.6 days, respectively p=0.012, effect sizes=0.5).

Although physical activity, technical performance and injury incidence were unaffected during a prolonged period of fixture congestion, injury rates during training and match-play and the lay-off duration were different to that reported in matches outside this period.

Ivarsson et al (2013). Psychological predictors of injury occurence: a prospective investigation of professional Swedish soccer players. J Sport Rehabil 22(1): 19-26

Athletes participating in sport are exposed to a high injury risk. Previous research has found a great number of risk factors (both physiological and psychological) that could increase injury risk. One limitation in previous studies is that few have considered the complex interaction between psychological factors in their research design. The aim of the study was to examine whether personality, stress, and coping predicted injury occurrence in an elite soccer population based on a hypothesized model. 56 (n = 38 male, n = 18 female) Swedish Premiere League soccer players were selected based on convenience sampling. Participants completed 4 questionnaires including the Swedish Universities Scales of Personality, Life Events Survey for Collegiate Athletes, and Brief COPE during the initial questionnaire administration. Subsequent to the first meeting, participants also completed the Hassle and Uplift Scale5 once per wk for a 13-wk period throughout the competitive season. A path analysis was conducted examining the influence of personality traits (ie, trait anxiety), state-level stressors (ie, negative-life-event stress and daily hassles), and coping on injury frequency. Results of the path analysis indicated that trait anxiety, negative-life-event stress, and daily hassle were significant predictors of injury among professional soccer players, accounting for 24% of the variance.

The findings highlight the need for athletes, coaches, and medical practitioners to attempt to reduce state-level stressors, especially daily hassles, in minimizing injury risk. Educating and training athletes and coaches in proactive stress-management techniques appears warranted.

Nedelec et al (2013). Recovery in soccer: part II-recovery strategies. Sports Med 43(1): 9-22

In the formerly published part I of this two-part review, we examined fatigue after soccer matchplay and recovery kinetics of physical performance, and cognitive, subjective and biological markers. To reduce the magnitude of fatigue and to accelerate the time to fully recover after completion, several recovery strategies are now used in professional soccer teams. During congested fixture schedules, recovery strategies are highly required to alleviate post-match fatigue, and then to regain performance faster and reduce the risk of injury. Fatigue following competition is multifactorial and mainly related to dehydration, glycogen depletion, muscle damage and mental fatigue. Recovery strategies should consequently be targeted against the major causes of fatigue. Strategies reviewed in part II of this article were nutritional intake, cold water immersion, sleeping, active recovery, stretching, compression garments, massage and electrical stimulation. Some strategies such as hydration, diet and sleep are effective in their ability to counteract the fatigue mechanisms. Providing milk drinks to players at the end of competition and a meal containing high-glycaemic index carbohydrate and protein within the hour following the match are effective in replenishing substrate stores and optimizing muscle-damage repair. Sleep is an essential part of recovery management. Sleep disturbance after a match is common and can negatively impact on the recovery process. Cold water immersion is effective during acute periods of match congestion in order to regain performance levels faster and repress the acute inflammatory process. Scientific evidence for other strategies reviewed in their ability to accelerate the return to the initial level of performance is still lacking. These include active recovery, stretching, compression garments, massage and electrical stimulation. While this does not mean that these strategies do not aid the recovery process, the protocols implemented up until now do not significantly accelerate the return to initial levels of performance in comparison with a control condition.

In conclusion, scientific evidence to support the use of strategies commonly used during recovery is lacking. Additional research is required in this area in order to help practitioners establish an efficient recovery protocol immediately after matchplay, but also for the following days. Future studies could focus on the chronic effects of recovery strategies, on combinations of recovery protocols and on the effects of recovery strategies inducing an anti-inflammatory or a pro-inflammatory response.

Elias et al (2012). Effectiveness of water immersion on post-match recovery in elite professional footballers. Int J Sports Physiol Perform Sept 4 [Epub ahead of print]

The efficacy of a single exposure to 14-min of contrast water therapy (CWT) or cold water immersion (COLD) on recovery post-match in elite professional footballers was investigated. Twenty four elite footballers participated in a match followed by one of 3 recovery interventions. Recovery was monitored for 48-hrs post-match. Repeat-sprint ability (6 x 20-m), static and countermovement jump performance, perceived soreness and fatigue were measured pre, immediately following, 24 and 48 h after the match. Soreness and fatigue were also measured 1 h post-match. Post-match, players were randomly assigned to complete passive recovery (PAS) (n=8), COLD (n=8) or CWT (n=8). Immediately post-match, all groups exhibited similar psychometric and performance decrements, which persisted for 48 h only in the PAS group. Repeat-sprinting performance remained slower at 24 and 48 h for PAS (3.9% and 2.0%) and CWT (1.6% and 0.9%) but was restored by COLD (0.2% and 0.0%). Soreness after 48 h was most effectively attenuated by COLD (ES 0.59±0.10) but remained elevated for CWT (ES 2.39±0.29) and PAS (ES 4.01±0.97). Similarly, COLD more successfully reduced fatigue after 48 h (ES 1.02±0.72) compared to CWT (ES 1.22±0.38) and PAS (ES 1.91±0.67). Declines in static and countermovement jump were ameliorated best by COLD.

An elite professional football match results in prolonged physical and psychometric deficits for 48 h. Cold water immersion was more successful at restoring physical performance and psychometric measures than CWT, with PAS being the poorest.

Nassis G (2012). Effect of altitude on football performance: analysis of the 2010 FIFA World Cup data. J Strength Cond Res May 29 [Epub ahead of print]

Laboratory studies show that altitude ascent impairs endurance performance. Limited data exist on football, and information from official matches are very scarce even for other team sports. The aim of this study was to examine the effect of altitude on football performance during the 2010 World Cup. It was hypothesized that: a) total distance covered, an index of endurance, would be reduced above the altitude of 580 m, and b) technical skills would be affected since altitude alters ball flight characteristics. Physical performance, goals scored and goal keepers' errors that resulted in goals conceded were recorded from the official game statistics of FIFA during the South Africa 2010 World Cup. Matches were played at: sea level (altitude: 0 m), 660 m, 1200-1400 m and 1401-1753 m. After testing for data normality, mean differences were checked with a one-way ANOVA. Results show a 3.1% lower total distance was covered by the teams during the matches played at 1200-1400 m and 1401-1753 m (p< 0.05) compared to sea level. Indices of technical skills including number of goals scored per game and errors made by the goal keepers that resulted in goals conceded, did not differ with altitude.

Playing football above 1200 m had negative effects on endurance but not technical skills during World Cup 2010 matches. It seems that teams should follow several days of acclimatization before playing at altitude as low as 1200 m, to ameliorate the negative effects of altitude on physical performance.

Source: PubMed

1 comment:

Gjält said...

"It seems that teams should follow several days of acclimatization before playing at altitude as low as 1200 m, to ameliorate the negative effects of altitude on physical performance."

Do you have any data that supports this conclusion? Considering this data you can only conclude that performance is hindered at altitudes as low as 1200 m.
Have searched for articles on performance gains from acclimatization protocols for approximately 1000 m, but haven't found any so far. It's possible that this altitude is high enough to hinder the total amount of meters ran (as it does in endurance sports), but an acclimatization protocol doesn't improve it in a sport like soccer.

Thanks for sharing these articles. Nice blog you have.