There exists an optimal cadence for cyclic activities that is most energetically efficient for a given power output. The metabolic costs are primarily associated with two factors: the cost of doing ‘internal work’ resulting in moving the limbs in a cyclic fashion, and the ‘external work’ done on the environment (e.g., a bicycle pedal) or the body’s center or mass (e.g., walking, running). Despite the prevalence of cross trainers in fitness settings, experiments investigating metabolic costs under varying cadences at a fixed mechanical power on these devices are scarce.
PURPOSE: To quantify the energy cost of using a cross trainer when the user varied cadence while the machine adjusted resistance to maintain a constant external power.
METHODS: Eighteen healthy subjects (11M, 7F; 35 ± 11 yr) attended one laboratory session during which they exercised on a cross trainer at a workload (150 ± 42 watts) eliciting approximately 75% of age-predicted maximum heart rate at a cadence of 130 steps/min, then worked at a faster and slower cadence in a counterbalanced order (110, 150 steps/min). Metabolic cost (kcal/min) was quantified via indirect calorimetry, and compared across conditions with a one-way repeated measures ANOVA (α = 0.05).
RESULTS: Our findings suggest that working at 150 steps/min elicited greater cost (13.24 kcal/min, P < 0.001) relative to 130 steps/min (12.19 kcal/min) and 110 steps/min (11.61 kcal/min).
CONCLUSIONS: Altering cadence, independent of altering the rate of external work done on the environment, can result in significant changes in metabolic demand while exercising on a cross trainer. These data suggest that the most energetically costly strategy involves increasing the cadence at which an exerciser works, suggesting that the role of performing internal work may be a limiting factor when exercising on a cross trainer at a sub-anaerobic threshold.
