Repeated-sprint training in heat and hypoxia: effect of exercise-to-rest ratio

Time-continuous analysis of muscle and cerebral oxygenation during repeated treadmill sprints under heat stress: a statistical parametric mapping study

PURPOSE

We examined how heat exposure affects muscle and cerebral oxygenation kinetics using statistical parametric mapping (SPM) during repeated treadmill sprints.

METHODS

Eleven recreationally active males performed three sets of five 5-s sprints with 25 s of recovery and 3 min between sets in hot (38 °C) and temperate (25 °C) conditions. Continuous measurements of muscle (vastus lateralis) and cerebral (prefrontal cortex) tissue oxygenation were obtained using near-infrared spectroscopy. One-way ANOVA SPM{F} statistics were applied to pooled sprint data, with each condition including 15 time-series (three sets of five sprints) combined. Each time-series included the sprint and subsequent recovery phases.

RESULTS

Muscle tissue saturation index further decreased in hot compared to temperate condition, from the middle of the 5-s sprint phase (~ 2.9 s) until the end of the recovery period (p < 0.001), while total hemoglobin concentration was significantly higher in the early phase of recovery (from 5.1 to 11.8 s, p = 0.003). Cerebral tissue saturation index decreased from 0.7 s to 13.0 s (p < 0.001) in the heat. Total hemoglobin concentration was lower in hot condition during both the sprint phase and the initial third of the recovery (from 0 to 11.7 s, p < 0.001), as well as during the recovery (from 20.5 to 24.8 s, p = 0.007).

CONCLUSION

Adding heat stress to repeating treadmill sprints further lowered muscle oxygenation levels during both the sprint and recovery phases, and limited cerebral tissue perfusion during the sprint and the initial recovery phases. The use of SPM for continuous analysis of near-infrared spectroscopy data provides new insights beyond summary statistics.

Effects of blood flow restriction on internal and external training load metrics during acute and chronic short-term repeated-sprint training in team-sport athletes

This study examined internal, external training loads, internal:external ratios, and aerobic adaptations for acute and short-term chronic repeated-sprint training (RST) with blood flow restriction (BFR). Using randomised crossover (Experiment A) and between-subject (Experiment B) designs, 15 and 24 semi-professional Australian footballers completed two and nine RST sessions, respectively. Sessions comprised three sets of 5-7 × 5-second sprints and 25 seconds recovery, with continuous BFR (45% arterial occlusion pressure) or without (Non-BFR). Banister's, Edwards', Lucia's training impulse, and session rating of perceived exertion training load (sRPETL) were calculated. External training loads were determined by total work done (TWD). Ventilatory threshold power outputs were assessed during a graded exercise test post-RST. Internal training loads were comparable between conditions, though BFR reduced (p < 0.02) TWD during acute (-4.9%) and short-term chronic (-10.0%) RST compared to Non-BFR. Furthermore, BFR increased (p = 0.049) the sRPETL:TWD ratio during short-term chronic (+14.8%), but not acute RST. First and second ventilatory threshold power outputs improved (+8.3% and + 4.2%, respectively) similarly for both groups following RST. Repeated exposure to progressively overloaded RST with BFR increases internal demands for a given workload, which may promote beneficial physiological adaptations compared to Non-BFR, though aerobic performance was not further enhanced.

Continuous blood flow restriction during repeated-sprint exercise increases peripheral but not systemic physiological and perceptual demands

This study examined the impact of continuous blood flow restriction (BFR) during repeated-sprint exercise (RSE) on acute performance, peripheral, systemic physiological, and perceptual responses. In a randomized crossover design, 26 adult male semi-professional and amateur team-sport players completed two RSE sessions (3 sets of 5 × 5-s sprints with 25 s of passive recovery and 3 min of rest) with continuous BFR (45% arterial occlusion; excluding during between-set rest periods) or without (non-BFR). Mean and peak power output were significantly lower (p < 0.001) during BFR compared to non-BFR (dz = 0.85 and 0.77, respectively). Minimum tissue saturation index during the sprints and rest periods was significantly reduced (p < 0.001) for BFR (dz = 1.26 and 1.21, respectively). Electromyography root mean square was significantly decreased (p < 0.01) for biceps femoris and lateral gastrocnemius muscles during BFR (dz = 0.35 and 0.79, respectively), but remained unchanged for the vastus lateralis muscle in both conditions. Oxygen consumption and minute ventilation were significantly reduced (both p < 0.01) for BFR (dz = 1.46 and 0.43, respectively). Perceived limb discomfort was significantly higher (p < 0.001) for BFR (dz = 0.78). No differences (p > 0.05) in blood lactate concentration or rating of perceived exertion were observed between conditions. Blood flow-restricted RSE reduced performance and likely increased the physiological and perceptual stimulus for the periphery with greater reliance on anaerobic glycolysis, despite comparable or decreased systemic demands.

Repeated-Sprint Training With Blood-Flow Restriction Improves Repeated-Sprint Ability Similarly to Unrestricted Training at Reduced External Loads

PURPOSE

This study examined performance and physiological adaptations following 3 weeks of repeated-sprint training (RST) with blood-flow restriction (BFR) or without (non-BFR).

METHODS

Twenty-six semiprofessional and amateur adult male team-sport players were assessed for repeated-sprint ability, anaerobic capacity, leg lean mass, neuromuscular function, and maximal aerobic capacity before and after RST. Participants completed 9 cycling RST sessions (3 sets of 5-7 × 5-s sprints, 25-s passive recovery, 3-min rest) over a 3-week period with BFR or non-BFR.

RESULTS

During RST sessions, the BFR group demonstrated lower mean power output compared with non-BFR (-14.5%; g = 1.48; P = .001). Significant improvements (P < .05) in mean and peak power output during repeated-sprint ability (+4.1%; g = 0.42, and + 2.2%; g = 0.25, respectively) and anaerobic capacity (+4.8%; g = 0.47, and + 4.7%; g = 0.32, respectively) tests, leg lean mass (+2.0%; g = 0.16), and peak aerobic power (+3.3%; g = 0.25) were observed from pretesting to posttesting without any between-groups differences. No significant changes (P > .05) were observed for maximal isometric voluntary contraction and maximal aerobic capacity. Peak rate of force development decreased (P = .003) in both groups following RST (-14.6%; g = 0.65), without any between-groups differences.

CONCLUSIONS

Repeated-sprint ability, anaerobic capacity, leg lean mass, and peak aerobic power improved following 3 weeks of RST; however, the addition of BFR did not further enhance adaptations. Interestingly, comparable improvements were achieved between groups despite lower external loads experienced during RST sessions with BFR.

Effects of 2 Different Protocols of Repeated-Sprint Training in Hypoxia in Elite Female Rugby Sevens Players During an Altitude Training Camp

OBJECTIVES

Repeated-sprint training in hypoxia (RSH) is an effective way of improving physical performance compared with similar training in normoxia. RSH efficiency relies on hypoxia severity, but also on the oxidative-glycolytic balance determined by both sprint duration and exercise-to-rest ratio. This study investigated the effect of 2 types of RSH sessions during a classic altitude camp in world-class female rugby sevens players.

METHODS

Sixteen players performed 5 RSH sessions on a cycle ergometer (simulated altitude: 3000 m above sea level [asl]) during a 3-week natural altitude camp (1850 m asl). Players were assigned to 2 different protocols with either a high (RSH1:3, sprint duration: 8-10 s; exercise-to-rest ratios: 1:2-1:3; n = 7) or a low exercise-to-rest ratio (RSH1:5, sprint duration: 5-15 s; exercise-to-rest ratios: 1:2-1:5; n = 9). Repeated-sprint performances (maximal and mean power outputs [PPOmax, and PPOmean]) were measured before and after the intervention, along with physiological responses.

RESULTS

PPOmax (962 [100] to 1020 [143] W, P = .008, Cohen d = 0.47) and PPOmean (733 [71] to 773 [91] W, P = .008, d = 0.50) increased from before to after. A significant interaction effect (P = .048, d = 0.50) was observed for PPOmean, with a larger increase observed in RSH1:3 (P = .003). No interaction effects were observed (P > .05) for the other variables.

CONCLUSION

A classic altitude camp with 5 RSH sessions superimposed on rugby-sevens-specific training led to an improved repeated-sprint performance, suggesting that RSH effects are not blunted by prolonged hypoxic exposure. Interestingly, using a higher exercise-to-rest ratio during RSH appears to be more effective than when applying a lower exercise-to-rest ratio.