Muscle oxygenation maintained during repeated sprints despite inspiratory muscle loading

Abstract

A high work of breathing can compromise limb oxygen delivery during sustained high-intensity exercise. However, it is unclear if the same is true for intermittent sprint exercise. This project examined the addition of an inspiratory load on locomotor muscle tissue reoxygenation during repeated-sprint exercise. Ten healthy males completed three experimental sessions of ten 10 s sprints, separated by 30 s of passive rest on a cycle ergometer. The first two sessions were “all-out’ efforts performed without (CTRL) or with inspiratory loading (INSP) in a randomised and counterbalanced order. The third experimental session (MATCH) consisted of ten 10 s work-matched intervals. Tissue saturation index (TSI) and deoxy-haemoglobin (HHb) of the vastus lateralis and sixth intercostal space was monitored with near-infrared spectroscopy. Vastus lateralis reoxygenation (ΔReoxy) was calculated as the difference from peak HHb (sprint) to nadir HHb (recovery). Total mechanical work completed was similar between INSP and CTRL (effect size: −0.18, 90% confidence limit ±0.43), and differences in vastus lateralis TSI during the sprint (−0.01, ±0.33) and recovery (−0.08, ±0.50) phases were unclear. There was also no meaningful difference in ΔReoxy (0.21, ±0.37). Intercostal HHb was higher in the INSP session compared to CTRL (0.42, ±0.34), whilst the difference was unclear for TSI (−0.01, ±0.33). During MATCH exercise, differences in vastus lateralis TSI were unclear compared to INSP for both sprint (0.10, ±0.30) and recovery (−0.09, ±0.48) phases, and there was no meaningful difference in ΔReoxy (−0.25, ±0.55). Intercostal TSI was higher during MATCH compared to INSP (0.95, ±0.53), whereas HHb was lower (−1.09, ±0.33). The lack of difference in ΔReoxy between INSP and CTRL suggests that for intermittent sprint exercise, the metabolic O2demands of both the respiratory and locomotor muscles can be met. Additionally, the similarity of the MATCH suggests that ΔReoxy was maximal in all exercise conditions.

The Respiratory System during Intermittent-Sprint Work: Respiratory Muscle Work and the Critical Distribution of Oxygen

“…Inspiratory muscle force development (calculated as the integral of inspiratory mouth pressure, multiplied by respiratory frequency) was similar to others who have shown vastus grater lateralis muscle deoxygenation with inspiratory loading during exercise [63]. In response, whole-body VO 2 measured at the mouth was elevated by 4-5% during both the sprint and recovery phases (Figure 2) [62]. This occurred even though total sprint work was similar between the conditions.…”

“…Hyperventilation readily occurs during high-intensity exercise and can constrain a fall in arterial O 2 and pH [75,76]. Though this was not directly examined in our research [62,65], some evidence of hyperventilation occurring during repeated-sprint exercise was present. As depicted by the data of a representative subject (Figure 5), the partial pressure of end-tidal oxygen (P ET O 2 ) and carbon dioxide (P ET CO 2 ) rose and fell respectively from baseline over the course of the repeated-sprint protocol [62].…”

“…However, competition between locomotor and respiratory muscle for available cardiac output does not appear to be a significant limiting factor of performance during repeated-sprint exercise. In our recent work, we examined the influence of inspiratory muscle loading on oxygenation trends in repeated-sprint exercise [62]. Participants were asked to perform ten 10-s cycle ergometer sprints, each separated by 30 s of passive rest.…”

“…Whereas during moderate intensities (50-75% VO 2max ), there is no change in vascular resistance or blood flow [23]. Even though repeated-sprint exercise can elicit >90% of VO 2 peak, it is not sustained throughout the entire protocol and can fluctuate between 70 and 90% of VO 2max between sprint and recover phases [50,62]. The fluctuation in metabolic demands between the phases likely minimises the potential for a competition for available cardiac output.…”

Repeated sprint cycling performance is not enhanced by ischaemic preconditioning or muscle heating strategies

“…Whilst observations in running tasks show no changes on RSA following IPC (Gibson, White, Neish, & Murray, 2013), recent research indicates IPC can augment peak power and force production in humans (Paradis-Deschênes, Joanisse, & Billaut, 2016;Patterson, Bezodis, Glaister, & Pattison, 2015), in addition to enhancing certain parameters of oxidative metabolism, including oxidative capacity, muscle oxygenation, oxygen extraction and aerobic metabolism in humans (Bailey et al, 2012;Cruz, de Aguiar, Turnes, Pereira, & Caputo, 2015;;de Groot et al, 2010;Kido et al, 2015Paradis-Deschênes et al, 2016. Enhancement of oxidative metabolism may improve RSA performance, given RSA induces maximal muscular reoxygenation rates (Rodriguez, Townsend, Aughey, & Billaut, 2019) and oxygen availability is a limiting factor in repeated sprinting which can significantly impact RSA outcomes Balsom, Gaitanos, Ekblom, & Sjödin, 1994). To date, it appears that both IPC and local muscle heating strategies can significantly impact sprint-type exercises (Beaven & Kilduff, 2018;Patterson et al, 2015), but the mechanisms mediating these performance improvements are likely different and remain poorly understood.…”