Functional differences in muscle engagement during aerobic exercises of the upper and lower limbs

Abstract

Current recommendations for enhancing the oxidative capacity of the body emphasize the effectiveness of aerobic training. However, traditional methods, such as cycling ergometry, primarily engage the muscles of the lower limbs, without utilizing the full potential of the skeletal musculature. This systematic review aimed to comparatively assess the volume of muscle groups involved in aerobic activity of the upper and lower limbs, in order to evaluate their contribution to cardiorespiratory and metabolic adaptations. Analysis of 15 studies revealed that standard cycling ergometer exercise involves approximately 6073 cm³ (6.407 kg) of muscle mass. Incorporating the activity of the upper limb muscles increases the total volume of active muscle tissue by 39.1%, reaching 8449 cm³ (8.913 kg). Qualitative literature analysis identified a high adaptive potential of the upper limb muscles, associated with their lower baseline mitochondrial-to-muscle fiber volume ratio, creating favorable conditions for intensive mitochondrial biogenesis. Calculations indicate that combined aerobic exercise can lead to a total increase in mitochondrial mass of up to 0.98 g, exceeding the effects of isolated lower-limb training. These findings support the inclusion of upper limb work in aerobic training programs to more fully engage the skeletal musculature and maximize the development of the body’s oxidative capacity. Such an approach contributes to enhanced cardiorespiratory and metabolic adaptations, increased aerobic power, and improved functional quality of muscles.