Buchheit M, Laursen PB, Ahmaidi S. Parasympathetic reactivation after repeated sprint exercise. Am J Physiol Heart Circ Physiol 293: H133-H141, 2007. First published March 2, 2007; doi:10.1152/ajpheart.00062.2007.-The purpose of this study was to examine the effects of muscular power engagement, anaerobic participation, aerobic power level, and energy expenditure on postexercise parasympathetic reactivation. We compared the response of heart rate (HR) after repeated sprinting with that of exercise sessions of comparable net energy expenditure and anaerobic energy contribution. Fifteen moderately trained athletes performed 1) 18 maximal all-out 15-m sprints interspersed with 17 s of passive recovery (RS), 2) a moderate isocaloric continuous exercise session (MC) at a level of mean oxygen uptake similar to that of the RS trial, and 3) a high-intensity intermittent exercise session (HI) conducted at a level of anaerobic energy expenditure similar to that of the RS trial. Subjects were immediately seated after the exercise trials, and beatto-beat HR was recorded for 10 min. Parasympathetic reactivation was evaluated through 1) immediate postexercise HR recovery, 2) the time course of the root mean square for the successive R-R interval difference between successive 30-s segments (RMSSD30s) and 3) HR variability vagal-related indexes calculated for the last 5-min stationary period of recovery. RMSSD30s increased during the 10-min period after the MC trial, whereas RMSSD 30s remained depressed after both the RS and HI trials. Parasympathetic reactivation indexes were similar for the RS and HI trials but lower than for the MC trial (P Ͻ 0.001). When data of the three exercise trials were considered together, only anaerobic contribution was related to HR trial-derived indexes. Parasympathetic reactivation is highly impaired after RS exercise and appears to be mainly related to anaerobic process participation.heart rate recovery; vagal-related indexes; autonomic activity; sprint interval training REPEATED SPRINT (RS) training, characterized by recurring sessions of brief repeated bouts of supramaximal exercise, may be a time-efficient strategy for inducing metabolic adaptations in human skeletal muscle (15). Adaptations shown after a short time course of RS training include increased resting glycogen content (20), increased maximal activities of various enzymes involved in glycolytic (31) and oxidative energy provision (10,20), an increased H ϩ buffer capacity (17,20), and decreased cycling time-trial performance (10,15,20). As a result, RS training has been proposed as a viable alternative to classically prescribed submaximal endurance training (10,17,20).Today, there are growing social and psychological reasons to encourage RS training within clinical populations. First, RS training is remarkably time efficient and more compatible with the Western world's time-poor modern lifestyle. Second, the concept of RS training may also be more attractive than continuous exercise for sedentary individuals who have difficulty han...

The aim of this study was to compare match performance in professional soccer players across two major European championships: Spanish La Liga and English FA Premier League (FAPL). Data were collected using a computerized match analysis system. A total of 5938 analyses were recorded during the 2006Á2007 season. The players were classified into six positional roles: central defenders, full backs, central defensive midfielders, wide midfielders, central attacking midfielders, and forwards. The match performance variables analysed included: (i) physical activity Á total distance covered, distances covered at high-intensities both with and without possession of the ball; (ii) technical actions Á heading and ground duels, passing, time in possession, and ball touches. Comparison of the total distance covered by FAPL and La Liga players showed no difference across individual playing positions but FAPL players generally covered greater distances in sprinting. In contrast, more of the total distance in sprinting was covered by La Liga players when their team was in possession (values from P B0.05 to P B0.001), while an equal total sprint distance, irrespective of possession, was observed in FAPL players. La Liga players won more heading duels (49.32% vs. 48.68%) and performed the same proportion of successful passes (76.17%). FAPL wide midfielders had Â20% more ball touches per possession than their La Liga counterparts (2.2490.54 vs. 2.0390.55, P B0.001). In conclusion, our results show that FAPL and La Liga teams present differences in various physical and technical aspects of match-play, suggesting that cultural differences may exist across professional soccer leagues and playing positions.

The aims of the present study were to (1) assess relationships between running performance and parasympathetic function both at rest and following exercise, and (2) examine changes in heart rate (HR)-derived indices throughout an 8-week period training program in runners. In 14 moderately trained runners (36 +/- 7 years), resting vagal-related HR variability (HRV) indices were measured daily, while exercise HR and post-exercise HR recovery (HRR) and HRV indices were measured fortnightly. Maximal aerobic speed (MAS) and 10 km running performance were assessed before and after the training intervention. Correlations (r > 0.60, P < 0.01) were observed between changes in vagal-related indices and changes in MAS and 10 km running time. Exercise HR decreased progressively during the training period (P < 0.01). In the 11 subjects who lowered their 10 km running time >0.5% (responders), resting vagal-related indices showed a progressively increasing trend (time effect P = 0.03) and qualitative indications of possibly and likely higher values during week 7 [+7% (90% CI -3.7;17.0)] and week 9 [+10% (90% CI -1.5;23)] compared with pre-training values, respectively. Post-exercise HRV showed similar changes, despite less pronounced between-group differences. HRR showed a relatively early possible decrease at week 3 [-20% (90% CI -42;10)], with only slight reductions near the end of the program. The results illustrate the potential of resting, exercise and post-exercise HR measurements for both assessing and predicting the impact of aerobic training on endurance running performance.

HIT was more effective than RS training at improving postexercise parasympathetic function and physical performance. In addition, HRRtau, which was more sensitive to training than HRV indices, seems to be a useful performance-related measurement.