EFFECTS OF A SUPRAMAXUMAL RUN TO EXHAUSTION ON RUNNING ECONOMY AND RUNNING KINEMATICS

The purpose of this study was to quantify total intra-individual variability in running economy (RE), Stride kinematics after a supramaximal run to exhaustion in French elite 400m runners. Ten runners took part in this study. All subjects had been following a training program for a minimum of 4 years and were experienced treadmill runners. They were selected after a maximal protocol to be homogeneous on V 02 max (63,5 * 2,l ml.kg-l.min -1 ) and on the speed reached with V02max (Vmax: 19 km.h-I). After completing a 15 rnin accommodation run, each subject performed a submaximal run, 6 rnin in length and 0% grade at 75% Vmax (14,5km.h-1). Following this run subjects completed a supramaximal run to exhaustion at 22 km.h-1 and 7% grade according to the protocol described by Schnabel and Kindermann (1983). Half an hour and one hour after this run, each subject repeated the 6 min submaximal run. During supramaximal run physiological parameters were continuously recorded. During each submaximal run, physiological parameters were recorded during the last 3 rnin and subjects were filmed between the second and the third minute. Stride rate was continuously recorded by an impact monitor fixed on the runner's right shoe. Results of physiological impact of the supramaximal run were in accordance with those found by Schnabel and Kindermann (1983) with the same population. Mean time to exhaustion was 98,2 * 16 sec and mean post exercise blood lactate peak was 16,71 * 2,31. No significant differences were found, after the supamaximal test, in running economy (39,8 vs 39,6 ml.kg-l.min-1, P>.05), and most of the stride kinematics with exception with plantar flexion at toe-off ( 70,9 vs 65,7 deg, P.05). The results of this study are in agreement with the study of Morgan et al. (1990) for a 30 rnin maximal run and moderately trained runners. It demonstrates that acute fatigue following a suparamaximal run to exhaustion does not increase the oxygen cost of submaximal running or alter stride kinematics over the short terzn. These results indicate, for elite runners and after a supramaximal run, the general stability of metabolic and kinematics parameters during a submaximal run. Key Words. Running economy, Stride Kinematics, Variability, Running

AGE-RELATED CHANGES IN NEUROMUSCULAR FUNCTION AND PERFORMANCE FOLLOWING A HIGH-INTENSITY INTERMITTENT TASK IN ENDURANCE TRAINED MEN

International audienceBackground: A greater attention has been focused on the need to design strategies to increase functional capacities in older populations. This has raised several questions regarding the ability of regular endurance training to preserve functional capacity with age.Objective: The purpose of this study was to examine the age-associated changes in neuromuscular function in endurance trained men before and after a high-intensity, intermittent fatigue task.Method: 26 healthy endurance trained male subjects: 16 old (59-79 yrs) and 10 young (20-34 yrs) men per-formed a high-intensity, intermittent fatigue exercise corresponding to 10 sets of 10 repetitions on a hori-zontal leg press at 70% of the individual one repetition maximum. Maximal voluntary contractions (MVC) and evoked contractions of the knee extensors muscles were performed before and after the exercise.Results: Decreases in MVC (old: -9.7 % and young: -14.3 %) and electromyographic activity were not different between groups. Peak twitch torque was reduced only for the old men and no changes in voluntary activa-tion and M-wave properties were recorded in either group.Conclusion: The present study indicates in endurance trained men aged 59-79 years that muscle functional capacities are maintained despite losses in strength and contractile function related to the age

Effects of high vs moderate-intensity training on neuroplasticity and functional recovery after focal ischemia

Background and Purpose: This study was designed to compare the effects of high-intensity interval training (HIT) and moderate-intensity continuous training (MOD) on functional recovery and cerebral plasticity during the first 2 weeks following cerebral ischemia. Methods: Rats were randomized as follows: Control (n=15), SHAM (n=9), MCAO (n=13), MCAO-D1 (n=7), MOD (n=13) and HIT (n=13). Incremental tests were performed at day 1 (D1) and 14 (D14) to identify the running speed associated with the lactate threshold (SLT) and the maximal speed (Smax). Functional tests were performed at D1, D7 and D14. Microglia form, cytokines, p75NTR, KCC2 and NKCC1 expression were made at D15. Results-HIT was more effective to improve the endurance performance than MOD and induced a fast recovery of the impaired forelimb grip force. The Iba-1 positive cells with amoeboid form and the pro- and anti-inflammatory cytokine expression were lower in HIT group, mainly in the ipsilesional hemisphere. A p75NTR overexpression is observed on the ipsilesional side together with a restored NKCC1/KCC2 ratio on the contralesional side. Conclusions-Low-volume HIT based on lactate threshold appears to be more effective after cerebral ischemia than work-matched MOD to improve aerobic fitness, grip strength and might promote cerebral plasticity

The impact of sleeping with reduced glycogen stores on immunity and sleep in triathletes.

PURPOSE: We investigated the effects of a 3-week dietary periodization on immunity and sleep in triathletes. METHODS: 21 triathletes were divided into two groups with different nutritional guidelines during a 3-week endurance training program including nine twice a day sessions with lowered (SL group) or maintained (CON group) glycogen availability during the overnight recovery period. In addition to performance tests, sleep was monitored every night. Systemic and mucosal immune parameters as well as the incidence of URTI were monitored every week of the training/nutrition protocol. Two-ways ANOVA and effect sizes were used to examine differences in dependent variables between groups at each time point. RESULTS: The SL group significantly improved 10 km running performance (-1 min 13 s, P < 0.01, d = 0.38), whereas no improvement was recorded in the CON group (-2 s, NS). No significant changes in white blood cells counts, plasma cortisol and IL-6 were recorded over the protocol in both groups. The vitamin D status decreased in similar proportions between groups, whereas salivary IgA decreased in the SL group only (P < 0.05, d = 0.23). The incidence of URTI was not altered in both groups. All participants in both groups went to bed earlier during the training program (SL -20 min, CON -27 min, P < 0.05, d = 0.28). In the SL group, only sleep efficiency slightly decreased by 1.1 % (P < 0.05, d = 0.25) and the fragmentation index tended to increase at the end of the protocol (P = 0.06). CONCLUSION: Sleeping and training the next morning regularly with reduced glycogen availability has minimal effects on selected markers of immunity, the incidence of URTI and sleeping patterns in trained athletes

Influence of age and sex on pacing during Sprint, Olympic, Half-Ironman and Ironman triathlons: Part B

The aim of this study was to investigate the influence of biological sex and age on the pacing strategies adopted by non-drafting top triathletes during the cycle and run disciplines of a Sprint, Olympic, half-Ironman and Ironman triathlon. Split times of the top 20% non-elite males (n=468) and females (n=146) were determined using official race transponders and a video capture system for pre-determined sections of the cycle and run disciplines of four triathlon distances. Indices of pacing were calculated to compare between sexes and age-groups. Results of this study indicated that different pacing strategies were adopted between athletes of different age and sex over the various triathlon disciplines and distances. Females were more aggressive during the initial stages of the cycling discipline across all distances (sprint - 2.1% p=0.024; Olympic - 1.6%, p=0.011; half-Ironman- 1.5%, p<0.001; Ironman - 1.7%, p<0.001 higher relative to mean) compare with males. Younger athletes (20-29 y) tend to begin the run faster (2.0 to 3.0% faster than other age-groups, p<0.029) during the sprint, Olympic and half-Ironman triathlons. These results indicate that different pacing strategies are adopted by non-drafting top athletes of different age and sex. Optimal pacing strategies may differ between sex and ages; therefore individuals may need to trial different strategies to develop their own optimal pacing profile for triathlon events of varying distances

Influence of race distance and biological sex on age-related declines in triathlon performance: Part A

This study examined the effect of biological sex and race distance on the age-related declines in swimming, cycling, running and overall performances of the sprint, Olympic, Half-Ironman and Ironman triathlons. Individual discipline and overall performance time of the top 20% non-elite males (n=468) and females (n=146) were compared by categorizing into four 10-year age-groups (20-29, 30-39, 40-49, 50+ years) and normalising to the mean performance time of the fastest age-group for each race. An earlier, larger and faster rate of decline (p=0.01) in performance with ageing was observed in females (≥30 years, 9.3%, 3.0% per decade respectively) and males (≥40 years, 5.9%, 2.2% per decade, respectively) for the longer events (half-Ironman and Ironman) compared with the shorter distances (sprint and Olympic, ≥50 years for both sexes). A greater magnitude of decline was observed in swimming for both sexes, especially in the longer events, when compared with cycling and running (12.8%, 5.6%, 9.3% for females, 9.4%, 3.7%, 7.3% for males, in the swim, cycle and run disciplines, respectively). These results indicate that both race distance and biological sex influence the age-related decline in triathlon performance and could aid athletes in optimising training programs to attenuate the age-related declines in performance across different disciplines and distances. Specifically, older athletes may benefit from greater emphasis on swim training and factors that may influence performance during longer distance triathlons

Enhanced Endurance Performance by Periodization of CHO Intake: "sleep low" strategy

Purpose: We investigated the effect of a chronic dietary periodization strategy on endurance performance in trained athletes. Methods: 21 triathletes (V[Combining Dot Above]O2max: 58.7 +/- 5.7 mL[middle dot]min-1[middle dot]kg-1) were divided into 2 groups: a "sleep-low" (SL, n = 11) and a control group (CON, n = 10) consumed the same daily carbohydrate (CHO) intake (6 g[middle dot]kg-1[middle dot]d-1) but with different timing over the day to manipulate CHO availability before and after training sessions. The "sleep low" strategy consisted of a 3-week training/diet intervention comprising three blocks of diet/exercise manipulations: 1) "train-high" interval training sessions (HIT) in the evening with high-CHO availability; 2) overnight CHO restriction ("sleeping-low"), and 3) "train-low" sessions with low endogenous and exogenous CHO availability. The CON group followed the same training program but with high CHO availability throughout training sessions (no CHO restriction overnight, training sessions with exogenous CHO provision). Results: There was a significant improvement in delta efficiency during submaximal cycling for SL versus CON (CON: +1.4 +/- 9.3 %, SL: +11 +/- 15 %, P<0.05). SL also improved supra-maximal cycling to exhaustion at 150% of peak aerobic power (CON: +1.63 +/- 12.4 %, SL: +12.5 +/- 19.0 %; P = 0.06) and 10 km running performance (CON: -0.10 +/- 2.03 %, SL: -2.9 +/- 2.15 %; P < 0.05). Fat mass was decreased in SL (CON: -2.6 +/- 7.4; SL: -8.5 +/- 7.4 %PRE, P < 0.01), but not lean mass (CON: -0.22 +/- 1.0; SL: -0.16 +/- 1.7 %PRE). Conclusion: Short-term periodization of dietary CHO availability around selected training sessions promoted significant improvements in submaximal cycling economy, as well as supra-maximal cycling capacity and 10 km running time in trained endurance athletes

Evaluation du potentiel énergétique des coureurs de haut niveau : relations entre des tests de laboratoire et la performance sur 400m

National audienceCette étude a été menéedans le cadre du diplômede l’INSEP grâce à la collaborationde Fernand Urtebise,Pierre Bonvin et Hervé Stéphan.Je tiens à remercier égalementles athlètes qui, malgré leuremploi du temps déjà bien rempli,ont accepté de participer àdes tests qui n’étaient pas toujourstrès agréables