Effect of cadence on locomotor-respiratory coupling during upper-body exercise

Abstract

Introduction: Asynchronous arm-cranking performed at high cadences elicits greater cardiorespiratory responses compared to low cadences. This has been attributed to increased postural demand and locomotor-respiratory coupling (LRC), and yet, this has not been empirically tested. This study aimed to assess the effects of cadence on cardiorespiratory responses and LRC during upper-body exercise.

Methods: Eight recreationally-active men performed arm-cranking exercise at moderate and severe intensities that were separated by 10 min of rest. At each intensity, participants exercised for 4 min at each of three cadences (50, 70, and 90 rev min^-1) in a random order, with 4 min rest-periods applied in-between cadences. Exercise measures included LRC via whole- and half-integer ratios, cardiorespiratory function, perceptions of effort (RPE and dyspnoea), and diaphragm EMG using an oesophageal catheter.

Results: The prevalence of LRC during moderate exercise was highest at 70 vs. 50 rev min^-1 (27 ± 10 vs. 13 ± 9%, p = 0.000) and during severe exercise at 90 vs. 50 rev min^-1 (24 ± 7 vs. 18 ± 5%, p = 0.034), with a shorter inspiratory time and higher mean inspiratory flow (p < 0.05) at higher cadences. During moderate exercise, [Formula: see text] and f _C were higher at 90 rev min^-1 (p < 0.05) relative to 70 and 50 rev min^-1 ([Formula: see text] 1.19 ± 0.25 vs. 1.05 ± 0.21 vs. 0.97 ± 0.24 L min^-1; f _C 116 ± 11 vs. 101 ± 13 vs. 101 ± 12 b min^-1), with concomitantly elevated dyspnoea. There were no discernible cadence-mediated effects on diaphragm EMG.

Conclusion: Participants engage in LRC to a greater extent at moderate-high cadences which, in turn, increase respiratory airflow. Cadence rate should be carefully considered when designing aerobic training programmes involving the upper-limbs.

Keywords: Arm-cranking; Cardiorespiratory; Diaphragm; Entrainment; Respiratory muscle.

Fig. 1

Locomotor–respiratory ratio calculated at 5 s intervals for a representative participant performing severe-intensity arm-crank exercise at 90 rev min⁻¹. Locomotion and respiration were considered to be matched when the instantaneous ratio recorded at 5 s intervals was within ±0.05 of a whole- or half-integer value. The prevalence of LRC in this representative example was 25%

Fig. 2

Locomotor–respiratory coupling (entrainment) during moderate (a) and severe (b) arm-crank exercise, and mean inspiratory flow (V _T/T _I) during moderate (c) and severe (d) arm-crank exercise performed at 50, 70, and 90 rev min⁻¹. During moderate exercise, the prevalence of LRC was highest at 70 rev min⁻¹, and during severe exercise at 90 rev min⁻¹. Mean inspiratory flow showed similar cadence-mediated patterns. *Significantly different vs. 50 rev min⁻¹ (p < 0.05); ^†significantly different vs. 70 rev min⁻¹ (p < 0.05)

Fig. 3

Oxygen uptake (a), cardiac frequency (b), ventilation (c), and tidal volume (d) during arm-cranking at moderate and severe intensities, performed at 50, 70, and 90 rev min⁻¹. Cardiorespiratory responses during moderate exercise were greater at higher cadences, but the differences were less apparent during severe exercise. *Significantly different vs. 50 rev min⁻¹ (p < 0.05); ^†significantly different vs. 70 rev min⁻¹ (p < 0.05)