- Title
- The acute physiological, physical and perceptual responses to intermittent hypoxic resistance training
- Creator
- Scott, Brendan Richard
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2016
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Recent evidence suggests that supplemental hypoxia during resistance training can enhance muscular adaptation. However, the mechanisms underpinning augmented muscular responses to intermittent hypoxic resistance training (IHRT) and how they can be optimised remain largely unknown. Therefore, the aim of this thesis was to examine the acute physiological, physical and perceptual responses to IHRT in well-trained participants. Study 1 quantified the inter- and intra-test reliability of electromyography (EMG) and near-infrared spectroscopy (NIRS) technologies during resistance exercise. Twelve well-trained young men (age: 24.8 ± 3.4 yr; height: 178.6 ± 6.0 cm; body mass: 84.8 ± 11.0 kg) performed high-load back squat exercise (12 sets at 70-90% of 1-repetition maximum [1RM]) on two occasions, with thigh muscle activation and oxygenation being monitored by EMG and NIRS, respectively. Intra-test reliability for EMG and NIRS variables was generally higher than inter-test reliability. NIRS-derived measures of muscle oxygenation were generally more reliable during single-repetition sets than multiple-repetition sets at the same load. Although the reliability of EMG and NIRS varied across the exercise protocol, the biological variation during multi-joint isoinertial resistance exercise may account for the fluctuations in the observed results. Study 2 aimed to determine whether different levels of hypoxia affect physical performance during high-load resistance exercise. Using a randomised single blind cross-over design, 12 resistance-trained males (age: 25.3 ± 4.3 yr; height: 179.0 ± 4.5 cm; body mass: 83.4 ± 9.1 kg) completed three trials of 5 x 5 repetitions of back squats and deadlifts at 80% 1RM with 180 s inter-set rest. Trials took place in normoxia (NORM; fraction of inspired oxygen [FIO₂] = 21%), moderate-level hypoxia (MH; FIO₂ = 16%), and high-level hypoxia (HH; FIO₂ = 13%). Physical performance was monitored during repetitions (force and power variables), and arterial oxygen saturation (SpO₂), heart rate (HR), and a rating of perceived exertion (RPE) were obtained following each set. No differences in performance were evident between conditions. HR was higher following sets in HH than NORM (p = 0.009), while SpO₂ was lower in hypoxic conditions than in NORM (p < 0.001). There were no differences in RPE between conditions. These findings suggest that physical performance and perceived effort during high-load resistance exercise is not affected by supplemental hypoxia. Study 3 assessed whether hypoxia during high-load resistance exercise could enhance the acute responses thought to underpin IHRT adaptation. Twelve well-trained males (age: 25.3 ± 4.3 yr; height: 179.0 ± 4.5 cm; body mass: 83.4 ± 9.1 kg) performed the same high-load resistance exercise protocol described for Study 2 in NORM, MH and HH. Muscle oxygenation and activation were monitored via NIRS and EMG, respectively. Blood lactate (BLa-) concentration and pH levels were assessed to quantify metabolic stress. Perceived fatigue and soreness were also quantified following the exercise. HH appeared to cause the lowest levels of muscle oxygenation during exercise, though significant differences between conditions were only observed for maximal deoxyhaemoglobin in the deadlift (p = 0.009). Metabolic stress increased from baseline following exercise (p ≤ 0.004), however there were no consistent between-condition differences. Muscle activation, perceived fatigue and soreness also did not differ between conditions. These data suggest that high-load IHRT may not provide added benefit over the equivalent normoxic training, possibly because of its inherent design with long inter-set rest periods. Study 4 assessed whether moderate-load IHRT with short rest periods could augment acute anabolic responses. Using a randomised single blind cross-over design, 14 well-trained male subjects (age: 24.6 ± 2.7 yr; height: 179.7 ± 5.9 cm; body mass: 84.6 ± 11.6 kg) performed resistance exercise trials in NORM and MH (3 x 10 repetitions of back squats and deadlifts at 60% 1RM with 60 s rest). SpO₂ and HR were assessed following each set, and BLa- concentration was quantified after each exercise. Thigh circumference was measured as a marker of muscle swelling. Muscle activation and oxygenation were monitored via EMG and NIRS, respectively. Relative BLa- concentrations were significantly higher following both squats (p = 0.041) and deadlifts (p = 0.002) in MH than NORM. SpO₂ was lower following each set in MH (p < 0.001), though there were no between-condition differences for HR or thigh circumference. Integrated EMG was higher in the MH trial at several time points for the back squat (p < 0.001), but not the deadlift. Muscle oxygenation did not differ between conditions. These data demonstrate that hypoxia during moderate-load resistance exercise with brief rest periods between sets can enhance metabolic stress in concert with increased muscle activation. Lastly, Study 5 aimed to determine whether hypoxia can affect markers of physical performance, training stress and neuromuscular recovery during moderate-load resistance exercise. Fourteen well-trained male subjects (age: 24.6 ± 2.7 yr; height: 179.7 ± 5.9 cm; body mass: 84.6 ± 11.6 kg) performed the same moderate-load resistance exercise protocol as for Study 4 in NORM and MH. Physical performance was quantified during repetitions (velocity and power). Perceived exertion, fatigue, soreness and wellbeing were assessed during and following exercise. Neuromuscular performance was monitored using vertical jump and isometric mid-thigh pull (MTP) tasks for up to 48 h following exercise. Performance declined across sets (p ≤ 0.010), though this was not different between conditions. Perceptual responses were also not different between conditions. Jump height and MTP peak force were decreased from pre-exercise values immediately after all trials (p ≤ 0.026), but returned to pre-exercise values at 24 h. Despite increases in metabolic stress and muscle activation (Study 4), physical performance and markers of training stress were not impacted by hypoxia during moderate-load resistance exercise. This collective work has highlighted the importance of structuring exercise using sufficient repetition volume and brief inter-set rest periods to elicit hypoxia-mediated benefits. Moderate-load IHRT with short rest in hypoxia was shown to enhance metabolic stress and muscle activation, which may maximise adaptation to resistance training. Importantly, supplementary hypoxia did not affect markers of training stress or recovery of neuromuscular function, making this an attractive strategy for already well-trained individuals.
- Subject
- strength training; muscle; hypoxia; metabolic stress; electromyography; near-infrared spectroscopy; thesis by publication
- Identifier
- http://hdl.handle.net/1959.13/1314606
- Identifier
- uon:22789
- Rights
- Copyright 2016 Brendan Richard Scott
- Language
- eng
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