Metabolic responses to soccer-specific intermittent exercise.

The intermittent exercise pattern associated with soccer makes analysis of the demands of the sport more complex than in many individual sports. The aim in this thesis was to determine the physiological and metabolic responses to soccer-specific exercise. The demands associated with elite level match-play were evaluated by techniques of motion-analysis. Laboratory based soccer-specific intermittent exercise protocols were then devised to determine the physiological strain associated with soccer and investigate the effects of increased ambient temperature and whole body pre-cooling on performance. The work-rate profiles of elite South American soccer players and English Premier League players, performing in international and club level respectively, were determined. English Premier League players covered a greater total distance during a game than the South American players (P< 0.05). Differences were found for the total distance covered for playing positions with midfield players covering larger distances than forwards. Defenders covered a greater distance jogging backwards than forward players with forwards sprinting a greater distance than defenders. Work-rate was reduced in the second half of the game for all player. The total distance covered by the international players was done mainly at submaximal intensities. High intensity exercise was infrequent and bouts were of short duration. No significant correlations were observed between the work-rate profile and anthropometric charactersitics of individuals. The use of the doubly-labelled water technique to indicate the energy expenditure during soccer match-play was investigated. The doubly-labelled water technique cannot determine energy expenditure during a soccer match as the rate of turnover of the isotopes is too small to allow the accurate estimation of energy expended. Laboratory based soccer-specific intermittent protocols elicited physiological responses that were similar in magnitude and pattern to soccer match-play. Physiological demands fluctuated with exercise intensity during intermittent exercise. Oxygen consumption and heart rate were not significantly different during soccer-specific intermittent exercise and steady-rate exercise at the same average intensity. Rectal temperature did not differ significantly between the two protocols, although intermittent exercise performance resulted in a greater rise in rectal temperature as the protocol progressed (P< 0.05). Sweat production did not differ significantly between the two exercise sessions, though the rating of perceived exertion was significantly higher (P< 0.05), for the session as a whole, during intermittent exercise. Intermittent exercise performance at 26 ° C did not result in significant increases in the physiological, metabolic or thermoregulatory responses when compared to intermittent exercise at 20 ° C. The physiological and metabolic responses were also similar when intermittent exercise was performed after a whole body pre-cooling manoeuvre. Rectal temperature was lowered by the pre-cooling strategy prior to exercise (- 0.6 ± 0.6 ° C, P< 0.05). Rectal temperature during exercise was only significantly lower after pre-cooling than during exercise at 26 ° C. No significant differences were observed in rectal temperature during exercise between the normal and pre-cooled condition. The increase in rectal temperature during the second half of the protocol was significantly greater than the increase observed at 26 ° C or under normal conditions. This may be a consequence of an altered thermoregulatory response due to the pre-cooling manouvre. In conclusion, the work-rate demands of soccer seem to be predominantly aerobic in nature with anaerobic bouts and the performance of specific match activities increasing the demands placed on players. The demands of intermittent exercise are not significantly different from continuous work performed at the same average intensity though there is tentative evidence for a decrease in the efficiency of the thermoregulatory system during intermittent work. No adverse effects upon intermittent exercise performance were noted under conditions of moderate heat stress, while any thermoregulatory benefits of whole body pre-cooling during intermittent work are probably only transient

The effect of concurrent training organisation in youth elite soccer players

Purpose: This study compared the adaptive responses to two concurrent training programmes frequently used in professional soccer. Methods: Fifteen youth soccer players (17.3 ± 1.6 years, 1.82 ± 0.06 m, 77.0 ± 7.3 kg; VO peak, 62.0 ± 4.7 ml kg min) who compete in the English Premier League volunteered for this study. In addition to completing their habitual training practices, the participants were asked to alter the organisation concurrent training by performing strength (S) training either prior to (S + E, n = 8) or after (E + S, n = 7) soccer-specific endurance training (E) 2d wk for 5 wk. Results: With the exception of 30 m sprint, IMVC PF, quadriceps strength (60°/s, 180°/s, 120°/s) pooled data revealed training effects across all other performances measures (P < 0.05). Whilst ANCOVA indicated no significant interaction effects for training condition, the difference between the means divided by the pooled standard deviation demonstrated large effect sizes in the E + S condition for in HBS 1-RM [S + E vs E + S; −0.54 (9.6 %) vs −1.79 (19.6 %)], AoP-M [−0.72 (7.9 %) vs −1.76 (14.4 %)], SJ [−0.56, (4.4 %), vs −1.08, (8.1 %)], IMVC-LR; [−0.50, (20.3 %) vs −1.05 (27.3 %)], isokinetic hamstring strength 60°/s [−0.64, (12.2 %) vs −0.95 (19.2 %)], 120°/s [−0.78 (27.9 %) vs −1.55 (23.3 %)] and isokinetic quadriceps strength 180°/s  [−0.23 (2.5 %) vs −1.52 (13.2 %)]. Conclusion: Results suggest the organisation of concurrent training, recovery time allocated between training bouts and the availability nutrition may be able to modulate small but clinically significant changes in physical performance parameters associated with match-play. This may have practical implications for practitioners who prescribe same day concurrent training protocols

Asymmetry after Hamstring Injury in English Premier League: Issue Resolved, Or Perhaps Not?

Hamstring injuries constitute one of the most concerning injuries in English Premier League football, due to its high primary incidence but also its recurrence. Functional methods assessing hamstring function during high-risk performance tasks such as sprinting are vital to identify potential risk factors. The purpose of this study was to assess horizontal force deficits during maximum sprint running on a non-motorized treadmill in football players with previous history of hamstring strains as a pre-season risk-assessment in a club setting. 17 male football players from one Premier League Club were divided into 2 groups, experimental (n= 6, age = 24.5 ± 2.3 years) and control (n= 11, age = 21.3 ± 1.2 years), according to history of previous hamstring injury. Participants performed a protocol including a 10 seconds maximum sprint on a non-motorized treadmill. Force deficits during acceleration phase and steady state phases of the sprint were assessed between limbs and between groups. The main outcome measures were horizontal and vertical peak forces during the acceleration phase or steady state. There were no significant differences in peak forces between previously injured and non-injured limbs, or between groups, challenging the ideas around functional force deficits in sprint running as a diagnostic measure of hamstring re-injury risk

Hormonal responses during two different concurrent-training trials in youth elite soccer players: does changing the organisation of training impact the hormonal response to concurrent exercise?

BACKGROUND: There are no data describing the acute hormonal responses to concurrent-training programmes in youth elite soccer players. Therefore, the aim of this study was to describe the total testosterone (T), cortisol (C), and growth hormone (hGH) responses during two same-day concurrent-training (CT) trials in elite soccer players. METHODS: n=13 youth elite players (age: 17.0±0.2 yrs; height, 1.80±0.07 m; body mass, 73.1±5.7 kg; O2 max, 64.4±4.8ml-1.kg-1.min-1) from an English premier league soccer club completed two CT trials. ‘Trial 1’ (CT1); E (10.30h) followed by S (14.00h) and Trial 2 (CT2); strength-training (S) 09.00h followed by a soccer-specific endurance-training session (E) at 10.30h. Venous blood samples were collected at 5 time-points around training and food intake (T1; 08.00h, T2; 09.45h, T3; 12.30h, T4; 13.45h and T5; 15.15h) and analysed for T (nmol/L) and C (nmol/L) and hGH (ug/L). RESULTS: There was no main effects found between exercise conditions for any hormones (T; P=0.22, C; P=0.07, hGH; P=0.21). Effect size analysis revealed a moderate effect for T at T3 (ES=0.63, CT1; 18.4±3.8, CT2; 15.7±4.7 nmol/L-1). A moderate effect for T area under the curve (AUC) was observed between conditions (CT1; 300±76 versus CT2; 244 ± 81 [AU]; ES=0.71). A moderate effect was apparent for C concentrations T4 in (ES=-0.95, CT1; 230±69, CT2; 314±105 nmol/L-1). Moderate effect sizes were observed at T3 and T4 (ES=0.82, CT1; 1.28±1.17, CT2; 0.47±0.75, ES=0.72, CT1; 0.11±0.05, CT2; 0.07±0.06 ug/L-1 respectively). A moderate effect for hGH AUC was observed between trials (CT1; 14±11 versus CT2; 5±9; [AU], ES=-1.08). CONCLUSIONS: The organisation of the concurrent-training protocols used in this study has a negligible impact upon the acute T, C and hGH in youth elite soccer players

Training load monitoring in team sports: A novel framework separating physiological and biomechanical load-adaptation pathways

There have been considerable advances in monitoring the training load in running-based team sports in recent years. Novel technologies nowadays offer ample opportunities to continuously monitor the activities of a player. These activities lead to internal biochemical stresses on the various physiological sub-systems. However, they also cause internal mechanical stresses on the various musculoskeletal tissues. Based on the amount and periodization of these stresses, the sub-systems and tissues adapt. So by monitoring external loads one hopes to estimate internal loads to predict adaptation, and this through understanding the load-adaptation pathways. We propose a new theoretical framework in which physiological and biomechanical load-adaptation pathways are considered separately, shedding a new light on some of the previously published evidence. We hope that it can help the various practitioners in this field (trainers, coaches, medical staff, sport scientists) to align their thoughts when considering the value of monitoring load, and that it can help researchers design experiments that can better rationalise training load monitoring for improving performance whilst preventing injury

TRIM63 (MuRF-1) Gene Polymorphism is Associated with Biomarkers of Exercise-Induced Muscle Damage

Unaccustomed strenuous exercise can lead to muscle strength loss, inflammation and delayed onset muscle soreness, which may be influenced by genetic variation. We investigated if a missense single nucleotide polymorphism (A>G, rs2275950) within the TRIM63 gene (encoding MuRF-1 and potentially affecting titin mechanical properties) was associated with the variable response to unaccustomed eccentric exercise. Sixty-five untrained, healthy participants (genotyped for rs2275950: AA, AG and GG) performed 120 maximal eccentric knee extensions (ECC) to induce muscle damage. Isometric and isokinetic maximal voluntary knee extension contractions (MVCs) and muscle soreness were assessed before, immediately after, and 48h after ECC. AA homozygotes were consistently stronger [baseline isometric MVC: 3.23±0.92 Nm/kg (AA) vs. 2.09±0.67 Nm/kg (GG); p=0.006] and demonstrated less muscle soreness over time (p=0.022) compared to GG homozygotes. This may be explained by greater titin stiffness in AA homozygotes, leading to intrinsically stronger muscle fibers that are more resistant to eccentric damaging contractions

A SEASON-LONG COMPARISON OF SOCCER REFEREE MATCH DEMANDS BETWEEN THE ENGLISH PREMIER LEAGUE AND CHAMPIONSHIP

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