Significant Molecular and Systemic Adaptations after Repeated Sprint Training in Hypoxia

Abstract

While intermittent hypoxic training (IHT) has been reported to evoke cellular responses via hypoxia inducible factors (HIFs) but without substantial performance benefits in endurance athletes, we hypothesized that repeated sprint training in hypoxia could enhance repeated sprint ability (RSA) performed in normoxia via improved glycolysis and O2 utilization. 40 trained subjects completed 8 cycling repeated sprint sessions in hypoxia (RSH, 3000 m) or normoxia (RSN, 485 m). Before (Pre-) and after (Post-) training, muscular levels of selected mRNAs were analyzed from resting muscle biopsies and RSA tested until exhaustion (10-s sprint, work-to-rest ratio 1∶2) with muscle perfusion assessed by near-infrared spectroscopy. From Pre- to Post-, the average power output of all sprints in RSA was increased (p<0.01) to the same extent (6% vs 7%, NS) in RSH and in RSN but the number of sprints to exhaustion was increased in RSH (9.4±4.8 vs. 13.0±6.2 sprints, p<0.01) but not in RSN (9.3±4.2 vs. 8.9±3.5). mRNA concentrations of HIF-1α (+55%), carbonic anhydrase III (+35%) and monocarboxylate transporter-4 (+20%) were augmented (p<0.05) whereas mitochondrial transcription factor A (−40%), peroxisome proliferator-activated receptor gamma coactivator 1α (−23%) and monocarboxylate transporter-1 (−36%) were decreased (p<0.01) in RSH only. Besides, the changes in total hemoglobin variations (Δ[tHb]) during sprints throughout RSA test increased to a greater extent (p<0.01) in RSH. Our findings show larger improvement in repeated sprint performance in RSH than in RSN with significant molecular adaptations and larger blood perfusion variations in active muscles.

No Improved Performance With Repeated-Sprint Training in Hypoxia Versus Normoxia: A Double-Blind and Crossover Study

“…Our main finding is that 12 RSH training sessions, compared with RSN, did not improve RS performance, when determined in 12 separate test sessions with and without prior exhausting exercise at sea level and normobaric hypoxia (FiO2=13. 3,4 . Such divergence could be explained by the absence of or controversial application of criteria for exhaustion/task failure 3,4 .…”

“…In this regard, the proposed effect of RSH on RS performance was observed without prior exercise and in normoxic conditions [2][3][4][5] . Whether such effect can be extrapolated to situations including prior exhaustive exercise (such as at the end of a XC-ski or bicycle race) and hypoxic conditions remains uncertain; if confirmed, RSH could be of major relevance for athletic competitions critically determined in fatiguing conditions and/or carried out at altitude 7 .…”

“…RSH is claimed to challenge skeletal muscle vasodilation and thereby trigger phenotypic modifications in peripheral vascular beds leading to increased oxygen delivery 2 . Indeed, previous studies have reported increased estimates of blood perfusion but unchanged activation of skeletal muscle during RS tests along with improvements in RS performance following RSH 3,4 . In particular, the number of repeated cycling and cross-country skiing double-poling sprints to exhaustion 3,4 and distance covered in the Yo-Yo intermittent recovery test 5 were further increased after 2-4 weeks of RSH vs. the same training under normoxic conditions (RSN) in moderately to highly endurance 3,4 and strength 5 trained young subjects.…”

“…In particular, the number of repeated cycling and cross-country skiing double-poling sprints to exhaustion 3,4 and distance covered in the Yo-Yo intermittent recovery test 5 were further increased after 2-4 weeks of RSH vs. the same training under normoxic conditions (RSN) in moderately to highly endurance 3,4 and strength 5 trained young subjects. However, the aforementioned studies present important limitations such as lack of double-blind design 3,5 or controversial/absent criteria for exhaustion in the RS test 3,4 .…”

β–alanine: performance effects, usage and side effects

“…Following four weeks of cycle sprint training (3 sets of 5×10 sec all-out repeated sprints with 5 min recovery), Faiss et al [263] showed that moderately trained males had improved activity of lactate dehydrogenase, suggesting an increased capacity for pH regulation [264]. Therefore in the present study, the second and third sets of repeated sprints would have been performed with a considerable stress on the mechanisms involved in intracellular pH regulation [227].…”