Effet d’une hyperventilation volontaire préexercice sur la performance lors de l’épreuve de Wingate

Aim

To determine the effect of a preexercise hyperventilation (HV) on performance measured during the Wingate test.

Protocol

Seven subjects realized the Wingate test whether in normal condition or after the realization of six maximal respiration cycles realized in 30 s. Gas exchanges were recorded breath by breath throughout the test.

Results

Pic power measured during the test was not significantly different after HV. In opposite, the fatigability index (FI) was significantly higher after HV.

Conclusion

A HV does not affect maximal power, but seems to reduce aerobic contribution, which may explain the higher FI observed after HV.     

The effect of lower limb occlusion on recovery following sprint exercise in academy rugby players

Objectives

The effects of vascular occlusion on recovery of physiological and neuromuscular markers over 24 h, and hormonal reactivity to subsequent exercise were investigated.

Reliability of a repeated-sprint test for field-hockey

The purpose of this study was to assess the reliability of a repeated-sprint test, specifically designed for field-hockey, as it was based directly on the time-motion analysis of elite level competition. The test consisted of 6 x 30-m over-ground sprints departing on 25s, with an active recovery (approximately 3.1-3.3 ms(-1)) between sprints. Ten highly trained, male, field-hockey players (mean+/-S.D.: age, 23+/-3 years; body mass, 78.1+/-7.1 kg) participated in this study. Following familiarisation, the subjects performed the repeated-sprint test on two occasions, 7 days apart. The reliability of the test variables was assessed by the typical error of measurement (TE). The total sprint time was very reliable (T(1): 26.79+/-0.76 s versus T2: 26.83+/-0.74 s), as the TE was 0.7% (95% CL, 0.5-1.2%). However, the percent sprint decrement was less reliable (T1: 5.6+/-0.9% versus T2: 5.8+/-1.0%), with the TE being 14.9% (95% CL, 10.8-31.3%). In summary, it is suggested that this field-hockey-specific, repeated-sprint test is very reliable when the results are presented as the total sprint time.     

Correlation of dynamic strength in the standing calf raise with sprinting performance in consecutive sections up to 30 meters

Sprinting represents a result-relevant task in many sports. The correlation of sprinting performance and one-repetition maximum (1RM) in a squat has been assumed as assured. Results of the correlation with 1RM of the plantar flexors are still pending. Assuming an increasing relevance of the reactive working capacity with increasing distance, a decrease of the influence of maximum strength of the calves is conceivable.

We investigated the correlation of 1RM in a calf raise and sprint performance in consecutive sections up to 30 meters. The results showed medium to strong, very significant correlations (p < 0.01) for absolute (r = ?0.483 to r = ?0.720) and relative (r = ?0.460 to ?0.577) strength, whereas an increase of the correlation throughout the course is observed.

The dynamic maximum strength of the calves is a basic prerequisite for short sprints and should be regarded as a performance reserve.     

Repeated high‐intensity exercise modulates Ca2+ sensitivity of human skeletal muscle fibers

The effects of short‐term high‐intensity exercise on single fiber contractile function in humans are unknown. Therefore, the purposes of this study were: (a) to access the acute effects of repeated high‐intensity exercise on human single muscle fiber contractile function; and (b) to examine whether contractile function was affected by alterations in the redox balance. Eleven elite cross‐country skiers performed four maximal bouts of 1300 m treadmill skiing with 45 min recovery. Contractile function of chemically skinned single fibers from triceps brachii was examined before the first and following the fourth sprint with respect to Ca²⁺ sensitivity and maximal Ca²⁺‐activated force. To investigate the oxidative effects of exercise on single fiber contractile function, a subset of fibers was incubated with dithiothreitol (DTT) before analysis. Ca²⁺ sensitivity was enhanced by exercise in both MHC I (17%, P < 0.05) and MHC II (15%, P < 0.05) fibers. This potentiation was not present after incubation of fibers with DTT. Specific force of both MHC I and MHC II fibers was unaffected by exercise. In conclusion, repeated high‐intensity exercise increased Ca²⁺ sensitivity in both MHC I and MHC II fibers. This effect was not observed in a reducing environment indicative of an exercise‐induced oxidation of the human contractile apparatus.     

Effect of acute and prolonged sprint training and a detraining period on lipid peroxidation and antioxidant response in rats

The purpose of this study was to determine the effect of sprint exercise and a detraining period on lipid peroxidation (malondialdehyde, MDA) and response of antioxidant system (ferric reducing ability of plasma (FRAP), uric acid, bilirubin and total protein). Forty-two male rats were divided randomly into two groups: sprint group (experimental) (n=24) and control group (n=18, without any training programme). The experimental group trained for 12 weeks, 3 times per week, with given intensities. Five trained rats experienced the detraining, so the effects of detraining were also studied (from the 8th to 12th weeks). Data were analysed using a two-way repeated ANOVA. A significant difference between the two groups was observed for MDA (p=0.022), FRAP (p=0.005) and bilirubin (p=0.002) but for total protein and uric acid no significant change occurred. In the experimental group, a significant difference was found through various assessments for MDA (p=0.001), FRAP (p=0.001), bilirubin (p=0.008) and uric acid (p=0.012). It can be concluded that this protocol of sprint exercise training causes adaptation in the antioxidant system and lipid peroxidation, but by detraining these results will be reversed.     

Warm-up or stretch as preparation for sprint performance?

Warm-up and stretching are widely used as techniques in preparation for intense physical activity, yet there is little information available to compare their effectiveness in relation to athletic performance. Fourteen elite Under-19 year old rugby league footballers undertook each of four preparation protocols (no preparation, stretching only, warm-up only, warm-up and stretching) in four successive testing sessions. Protocols were randomly allocated to players in a counterbalanced design so that each type of preparation occurred equally on each day of testing. During each session, athletes performed three solo sprint trials at maximum speed. Sprints were of 40-m distance and were electronically timed with wind speed and direction recorded. Preparation involving warm-up resulted in significantly faster sprint times compared to preparations having no warm-up, with a diminishing effect over the three trials. On the first trial, warm-up resulted in a mean advantage of 0.97 m over 40 m. Stretching resulted in a mean disadvantage of 0.18 m on the first trial, and no significant effect overall despite significant wind assistance. Warm-up was effective at improving immediate sprint performance, whereas an equivalent duration of lower limb stretching had no effect.     

The use of an eccentric chainring during an outdoor 1 km all-out cycling test

This study assessed whether an eccentric chainring that increases crank arm length at the downstroke and decreases it during the upstroke improves performance in a track cycling event: the 1000m time trial. It also determined whether selected physical and physiological variables and the velocity profile are associated with eccentric chainring performance. Twelve cyclists performed an outdoor 1000m time trial on a 333m banked, cement-surfaced track using two different chainrings, round and eccentric, in randomised order. The important findings of this study were that (1) performance did not significantly differ between chainrings; (2) neither the physiological variables (lactate and heart rate) nor the velocity profile (lap times) were affected by use of the eccentric design; (3) when time was saved with the eccentric chainring, it was significantly correlated with estimated lower limb muscle volume (r=-0.605), circumference (r=-0.739), estimated calf muscle volume (r=-0.772) and cross-sectional area (r=-0.745). Moreover, estimated lower limb muscle volume (r=-0.703), estimated calf muscle volume (r=-0.772) and cross-sectional area (r=-0.871) significantly predicted performance with the eccentric chainring. The physical variables associated with eccentric chainring performance were muscle anthropometric parameters. We have interpreted our results cautiously and suggest that the subjects who had greater lower limb muscle volume and greater calf muscle volume, seem to have had a significant advantage in performing with the eccentric chainring. Further testing with track specialists performing at national or international level would be helpful to define the maximal possibilities of this chainring.     

How much is enough in rehabilitation? High running workloads following lower limb muscle injury delay return to play but protect against subsequent injury

Objectives

Examine the influence of rehabilitation training loads on return to play (RTP) time and subsequent injury in elite Australian footballers.

The effects of the Nordic hamstring exercise on sprint performance and eccentric knee flexor strength: A systematic review and meta-analysis of intervention studies among team sport players

ObjectivesThe primary aim of this study was to investigate the effects of the Nordic hamstring exercise (NH_E) on sprint performance (i.e., 5, 10 and 20 m) and explore associations between study characteristics and sprint outcomes in team sport players. Secondary aims were to (1) investigate the effects of the NH_E on eccentric strength of the knee flexors (ES_KF) with categorical subgroup analysis to determine differences between recreationally, well-trained individuals and young athletes, (2) determine the relation between ES_KF and sprint performance in team sport players, and (3) explore the effect of study characteristics (i.e., weekly volume, time duration and body mass) on ES_KF.MethodsElectronic databases were searched until the 20th of June 2020. 17 studies met the inclusion criteria. Random-effects meta-analyses were used to determine the mean difference (MD) or standardized change of mean difference (SCMD) between NH_E and control group for sprint time and ES_KF, respectively.ResultsNH_E interventions showed a positive effect on sprint performance (−0.04 s [−0.08, −0.01]). Sub-group meta-analyses indicated no significant differences in 5 and 20 m sprint performance (MD_sprint(5m) = −0.02 s [−0.10, 0.06]) and (MD _sprint(20m) = −0.05 s [−0.30, 0.19]), respectively. A significant difference was however found for 10 m sprint performance (MD_sprint(10m) = −0.06 s [−0.10, −0.01]). Meta-analysis on the effects of the NH_E on ES_KF showed a significant benefit of 0.83 SCMD [0.55, 1.12] in favour of the intervention group.ConclusionsStudies with some concerns or high risk of bias show that training programs involving the NH_E can have small beneficial effects on sprint performance in team sport players. Studies with some concerns or high risk of bias showed moderate beneficial effects on ES_KF among a sample of relatively untrained individuals. However, for well-trained team sport players, the improvements in ES_KF were less consistent, suggesting a higher training intensity during the NH_E may be required to induce adaptations.