Author(s): RABERIN, A., CARLETTA, M., FRANCHI, N., CITHERLET, T., MANFERDELLI, G., MILLET, G.P., Institution: UNIVERSITÉ DE LAUSANNE: UNIVERSITE DE LAUSANNE, Country: SWITZERLAND, Abstract-ID: 447

INTRODUCTION:
Repeated sprint training in hypoxia (RSH) was shown as an effective method for enhancing repeated sprint ability. Since the required hypoxic device is not always available throughout a season or for each athlete, an alternative method called repeated sprint training with hypoventilation at low lung volume (RSH-VHL) was developed to induce a hypoxic stress. However, it also generates acidosis and hypercapnia. Recently, the concept of exercising with bouts of end-expiratory breath-hold until the voluntary breaking point (UBP) has been proposed, offering an even more hypoxemic and hypercapnic stimulus during high-intensity interval training, although this has not been applied specifically to repeated-sprints training.
Therefore, the objective of this study was to compare the physiological responses of repeated sprint training in normoxia (RSN), RSH-VHL, and repeated sprint training during end-expiratory breath-hold until the breaking point (RSH-UBP). Due to putative higher hypoxic and hypercapnic stress, we hypothesized a greater amplitude in stroke volume changes and muscle deoxygenation/reoxygenation (i.e., Tissue Saturation Index, TSI) during RSH-UBP compared to RSH.
METHODS:
Ten healthy active men performed 3 sessions of sprint training (2 sets of 8 sprints with 5 min of rest between sets; exercise:rest ratio of 1:2) in a randomized order. Sprint duration was 10 s for RSN and RSH-VHL conditions, while it depended on the apnea duration for RSH-UBP. Pulse oxygen saturation (SpO2), gas exchange, cardiac hemodynamics, muscle oxygenation, and total work were continuously recorded during the sessions.
RESULTS:
The time spent <96% of SpO2 (all p<0.010) and mean end tidal carbon dioxide pressure (all p<0.001) during the exercise bouts were higher in both RSH-VHL (81±65 s and 33.6±4.2 mmHg) and RSH-UBP (74±57 s and 32.9±3.5 mmHg) than in RSN (11±14 s and 27.8±4.2 mmHg). The pH similarly decreased from pre- to post-session between sprint modalities (p=0.137). Total work was lower (p<0.001) during RSH-UBP (33.1±5.8 kJ) compared to RSH-VHL (46.5±5.7 kJ) or RSN (47.4±6.0 kJ). Stroke volume and cardiac output did not differ between sprint modalities (all p>0.4). Amplitude in TSI changes was smaller (p<0.050) during RSH-UBP (7.0±4.3%) compared to RSH-VHL (10.3±6.0%) but not compared to RSN (10.3±7.1%).
CONCLUSION:
While RSH-UBP induced a greater hypoxic and hypercapnic stress than RSN, no difference was observed when compared to RSH-VHL. The reduction in total work during RSH-UBP was attributed to participants inability to maintain long-enough apnea, leading to a decrease in sprint duration. Consequently, the muscle deoxygenation level during RSH-UBP appeared blunted.
In conclusion, acutely, RSH-VHL appeared as a more effective condition than RSH-UBP. Further interventional training studies comparing the two strategies are required to assess if RSH-VLH can better preserve training load and elicit consistent physiological adaptations.