Manipulating exercise and recovery to enhance adaptations to sprint interval training

Highly-trained athletes are accustomed to varied and high-volume based exercise stimuli and eliciting adaptation in individuals already possessing the necessary physiology to compete at the highest level is difficult. Therefore, identifying novel, potent and time efficient methods of achieving cumulative training stress is a continual quest for coaches and exercise scientists. This thesis examined the acute and chronic effects of manipulating exercise and recovery during brief all-out sprint cycling on adaptive responses favouring enhanced endurance capacity. Chapter 3 highlighted that low-volume non-work matched all-out sprint cycling, whether it be interval- (4 x 30 s bouts) or continuous based (1 x 2 min bout) provides a similarly potent stimulus for the acute induction of cell signalling pathways and key growth factors associated with mitochondrial biogenesis and angiogenesis in trained individuals. In line with manipulating recovery and in attempting to identify a novel and potent exercise intervention capable of giving athletes more return on their training investment, Chapters 4-6 investigated the efficacy of combining sprint interval training with post-exercise blood flow restriction (BFR). Firstly, it was demonstrated that BFR potentiates HIF-1α mRNA expression in response to SIT, tentatively suggesting an enhanced stimulus for hypoxia- and/or metabolic-mediated cell signalling associated with mitochondrial biogenesis and angiogenesis over SIT alone. Secondly, four weeks of SIT combined with post-exercise BFR provides a greater training stimulus over SIT alone in trained individuals to enhance VO2max (4.7 v 1.1 % change) and MAP (3.8 v 0.2 % change), but not 15-km TT performance. Finally, in response to four weeks of SIT combined with post-exercise BFR, an international female track sprint cyclist increased her CP and W by 7 and 2 % and VO2max and absolute MAP by 3 and 4 %, respectively. Through a combination of an acute in vivo molecular experiment, a training study and an athlete case study, this thesis has introduced a potentially potent and novel training concept that appears capable of augmenting aerobic capacity

Acute and chronic effect of sprint interval training combined with post-exercise blood flow restriction in trained individuals

New Findings What is the central question of this study? Does the combination of sprint interval training with postexercise blood-flow restriction enhance maximal aerobic physiology and performance in trained individuals? What is the main finding and its importance? We demonstrate the potency of combining blood-flow restriction with sprint interval training in increasing maximal oxygen uptake in trained individuals; however, this did not translate to an enhanced exercise performance. We also show that blood-flow restriction combined with sprint interval training enhanced postexercise hypoxia-inducible factor-1α mRNA expression, suggesting the possibility for greater hypoxia-mediated adaptations, such as enhanced capillary growth, with this intervention. This investigation assessed the efficacy of sprint interval training (SIT) combined with postexercise blood-flow restriction as a novel approach to enhance maximal aerobic physiology and performance. In study 1, a between-groups design was used to determine whether 4 weeks (2 days per week) of SIT (repeated 30 s maximal sprint cycling) combined with postexercise blood-flow restriction (BFR) enhanced maximal oxygen uptake (inline image) and 15 km cycling time-trial performance (15 km TT) compared with SIT alone (CON) in trained individuals. The inline image increased after BFR by 4.5% (P = 0.01) but was unchanged after CON. There was no difference in 15 km TT performance after CON or BFR. In study 2, using a repeated-measures design, participants performed an acute bout of either BFR or CON. Muscle biopsies were taken before and after exercise to examine the activation of signalling pathways regulating angiogenesis and mitochondrial biogenesis. Phosphorylation of p38MAPKThr180/Tyr182 increased by a similar extent after CON and BFR. There was no difference in the magnitude of increase in PGC-1α, VEGF and VEGFR-2 mRNA expression between protocols; however, HIF-1α mRNA expression increased (P = 0.04) at 3 h only after BFR. We have demonstrated the potency of combining BFR with SIT in increasing inline image in trained individuals, but this did not translate to an enhanced exercise performance. Sprint interval training alone did not induce any observable adaptation. Although the mechanisms are not fully understood, we present preliminary evidence that BFR leads to enhanced HIF-1α-mediated cell signalling

Exercise duration-matched interval and continuous sprint cycling induce similar increases in AMPK phosphorylation, PGC-1α and VEGF mRNA expression in trained individuals

Purpose: The effects of low-volume interval and continuous ‘all-out’ cycling, matched for total exercise duration, on mitochondrial and angiogenic cell signalling was investigated in trained individuals. Methods: In a repeated measures design, 8 trained males ((Formula presented.), 57 ± 7 ml kg−1 min−1) performed two cycling exercise protocols; interval (INT, 4 × 30 s maximal sprints interspersed by 4 min passive recovery) or continuous (CON, 2 min continuous maximal sprint). Muscle biopsies were obtained before, immediately after and 3 h post-exercise. Results: Total work was 53 % greater (P = 0.01) in INT compared to CON (71.2 ± 7.3 vs. 46.3 ± 2.7 kJ, respectively). Phosphorylation of AMPKThr172 increased by a similar magnitude (P = 0.347) immediately post INT and CON (1.6 ± 0.2 and 1.3 ± 0.3 fold, respectively; P = 0.011), before returning to resting values at 3 h post-exercise. mRNA expression of PGC-1α (7.1 ± 2.1 vs. 5.5 ± 1.8 fold; P = 0.007), VEGF (3.5 ± 1.2 vs. 4.3 ± 1.8 fold; P = 0.02) and HIF-1α (2.0 ± 0.5 vs. 1.5 ± 0.3 fold; P = 0.04) increased at 3 h post-exercise in response to INT and CON, respectively; the magnitude of which were not different between protocols. Conclusions: Despite differences in total work done, low-volume INT and CON ‘all-out’ cycling, matched for exercise duration, provides a similar stimulus for the induction of mitochondrial and angiogenic cell signalling pathways in trained skeletal muscle

The acute angiogenic signalling response to low-load resistance exercise with blood flow restriction

This study investigated protein kinase activation and gene expression of angiogenic factors in response to low-load resistance exercise with or without blood flow restriction (BFR). In a repeated measures cross-over design, six males performed four sets of bilateral knee extension exercise at 20% 1RM (reps per set = 30:15:15:continued to fatigue) with BFR (110 mmHg) and without (CON). Muscle biopsies were obtained from the vastus lateralis before, 2 and 4 h post-exercise. mRNA expression was determined using real-time RT-PCR. Protein phosphorylation/expression was determined using Western blot. p38MAPK phosphorylation was greater (p = 0.05) at 2 h following BFR (1.3 ± 0.8) compared to CON (0.4 ± 0.3). AMPK phosphorylation remained unchanged. PGC-1α mRNA expression increased at 2 h (5.9 ± 1.3 vs. 2.1 ± 0.8; p = 0.03) and 4 h (3.2 ± 0.8 vs. 1.5 ± 0.4; p = 0.03) following BFR exercise with no change in CON. PGC-1α protein expression did not change following either exercise. BFR exercise enhanced mRNA expression of vascular endothelial growth factor (VEGF) at 2 h (5.2 ± 2.8 vs 1.7 ± 1.1; p = .02) and 4 h (6.8 ± 4.9 vs. 2.5 ± 2.7; p = .01) compared to CON. mRNA expression of VEGF-R2 and hypoxia-inducible factor 1α increased following BFR exercise but only eNOS were enhanced relative to CON. Matrix metalloproteinase-9 mRNA expression was not altered in response to either exercise. Acute low-load resistance exercise with BFR provides a targeted angiogenic response potentially mediated through enhanced ischaemic and shear stress stimuli

The combined effect of sprint interval training and blood flow restriction on critical power, capillary growth and mitochondrial proteins in trained cyclists

Sprint interval training (SIT) combined with post-exercise blood-flow restriction (BFR) is a novel method to increase maximal oxygen uptake (V̇ O2max) in trained individuals, and also provides a potent acute stimulus for angiogenesis and mitochondrial biogenesis. The efficacy to enhance endurance performance has however yet to be demonstrated. 21 trained male cyclists (V̇ O2max; 62.8 ± 3.7 ml.min-1 .kg-1 ) undertook 4 weeks of SIT (repeated 30 sec maximal sprints) either alone (CON; n = 10) or with post-exercise BFR (n = 11). Before and after training V̇ O2max, critical power (CP) and Wʹ were determined and muscle biopsies obtained for determination of skeletal muscle capillarity and mitochondrial protein content. CP increased (P = 0.001) by a similar extent following CON (287 ± 39 W to 297 ± 43 W) and BFR (296 ± 40 W to 306 ± 36 W). V̇ O2max increased following BFR by 5.9% (P = 0.02) but was unchanged after CON (P = 0.56). All markers of skeletal muscle capillarity and mitochondrial protein content were unchanged following either training intervention. In conclusion, 4 weeks of SIT increased CP, however this was not enhanced further with BFR. SIT was not sufficient to elicit changes in skeletal muscle capillarity and mitochondrial protein content with or without BFR. However, we further demonstrate the potency of combining BFR with SIT to enhance V̇ O2max in trained individuals