Effect of priming exercise and body position on pulmonary oxygen uptake and muscle deoxygenation kinetics during cycle exercise

Abstract

We hypothesized that the performance of prior heavy exercise would speed pulmonary oxygen uptake (VO2) kinetics (i.e. described by a time constant, τVO2) and reduce the amplitude of muscle deoxygenation (deoxy[heme]) kinetics in the supine (S) but not upright (U) body positions. 17 healthy men completed heavy intensity constant work rate exercise tests in S and U consisting of two bouts of 6 min cycling separated by 6 min cycling at 20 W. Pulmonary VO2 was measured breath-by-breath; total- and deoxy[heme] were determined via time-resolved-NIRS at three muscle sites. Priming exercise reduced τVO2 in S (bout 1: 36 ± 10 vs. bout 2: 28 ± 10 s, P < 0.05) but not U (bout 1: 27 ± 8 vs. bout 2: 25 ± 7 s, P > 0.05). The deoxy[heme] amplitude was increased following priming in S (bout 1: 25-28 vs. bout 2: 30-35 μM, P < 0.05) but not U (bout 1: 13-18 vs. bout 2: 17-25 μM, P > 0.05), whereas baseline total[heme] was enhanced in S (bout 1: 110-179 vs. bout 2: 128-185 μM, P < 0.05) and U (bout 1: 123-186 vs. bout 2: 137-197 μM, P < 0.05). Priming exercise increased total[heme] in both S and U, likely indicating enhanced diffusive O2 delivery. However, the observation that following priming the amplitude of the deoxy[heme] response was increased in S suggests that the reduction in τVO2 subsequent to priming was related to a combination of both enhanced intracellular O2 utilization and increased O2 delivery.

Interaction of Factors Determining Critical Power

“…reduce 𝜏 VO2 ) during upright cycle exercise in young healthy individuals. However, during exercise in the supine position, muscle perfusion pressure is impaired and 𝜏 VO2 becomes O 2 delivery dependent [114][115][116][117][118][119][120]. Hence, in a young healthy population, prior heavy exercise (which enhances muscle O 2 delivery, [115,121,122]) would be expected to reduce 𝜏 VO2 during supine but not upright cycling.…”

“…In practice, the exercise transition is undertaken by muscle fibres across the spectrum of function, with differing underlying oxidative phosphorylation activities, each-step activation intensities, convective and diffusive O 2 supply, and fatigue characteristics [139][140][141]. Additionally, the location of a given fibre with respect to the skin surface has implications for the relative O 2 delivery [45,[118][119][120]142]. Nevertheless, findings at the whole muscle level are congruent with the notion that metabolic inertia at the onset of exercise determines CP via its effect on the accumulation of Pi and other O 2 deficit-related metabolites that are implicated in the fatigue process.…”

How Priming Exercise Affects Oxygen Uptake Kinetics: From Underpinning Mechanisms to Endurance Performance

“…3 A). For instance, prior heavy exercise performed in the supine or prone positions reduces during subsequent heavy exercise [ 2 , 7 , 16 , 54 , 55 ]. Moreover, prior heavy exercise reduced during subsequent moderate exercise in healthy elderly individuals [ 56 ], patients with type 2 diabetes mellitus [ 57 , 58 ] and heart failure [ 59 ], and healthy individuals with initially slow kinetics [ 60 ], in contrast to healthy young active individuals.…”

“…The physiological mechanisms underpinning the effect of prior exercise on O 2 kinetics and subsequent performance, however, are difficult to pinpoint as priming upregulates multiple steps in the O 2 transport and utilisation pathways. As a result, the primary factors responsible are still a matter of intense debate [ 7 – 9 ]. The purpose of this review is to summarise the advancements in understanding that have been made since the 2003 review in this journal on the same topic [ 10 ].…”

Feasibility and early effects of bed‐cycling eccentric training: Potential clinical applications

“…Since the strength produced by the vastus laterali s, which is part of the Quadriceps muscle, depends on the knee and hip flexion angle, body position is a crucial parameter for cycle training efficiency (Bordoni & Varacallo, 2022). During supine exercise where the active musculature is at or above the level of the heart, the gravitational assistance to muscle blood flow is absent and muscle perfusion pressure is reduced resulting in slowed tissues oxygenation (Goulding et al, 2020; Jones et al, 2006; Macdonald et al, 1998). This posture dependent alteration in active muscles perfusion could explain why performance on cycle ergometer is improved in the standing position (Astrand & Saltin, 1961).…”