Mackintosh, K. A. | Search bioRxiv

bioRxiv2026

Cardiorespiratory fitness and sex impact the colorectal cancer-suppressive effects of aerobic exercise serum

Post-exercise human serum treatment can exhibit anti-viability properties in various cancer cell lines. However, whether the presence and/or magnitude of the effect differs in different participant populations is yet to be established. Here, we characterised baseline differences in serum-stimulated colorectal cancer cell viability and the acute exercise-induced response in males and females with varying levels of cardiorespiratory fitness (CRF). Forty-one participants (13 female) were stratified by maximal exercise test-derived VO2peak into high (n = 20) and low CRF (n = 21) and completed two experimental trials in a randomised crossover design: (1) 30-min moderate-intensity aerobic exercise; and (2) 30-min seated rest. Serum samples were collected before (pre), immediately after (post0), and 60-min after (post60) each trial and used to treat the human colorectal cancer cell line Caco-2 for 48 h, with cell viability assessed by MTT assay. Exercise-induced alterations in Caco-2 cell viability were, at least in part, modulated by CRF and sex. Specifically, at post0 and post60, exercise serum significantly reduced cell viability compared with no-exercise control serum when derived from individuals with high but not low CRF, and when derived from males but not females. These findings provide the first insights into the role of individual characteristics in determining the effects of exercise on colorectal cancer cells, with potential implications for increasing the precision of exercise recommendations for colorectal cancer risk reduction.

physiology↗

bioRxiv2020

Path tortuosity changes the transport cost paradigm in terrestrial animals

Animal movement paths are variously tortuous, with high turn rates predicted to be energetically costly, especially at high speeds. Animals travel most efficiently at the speed that gives the lowest cost of transport (COT), a well-defined point for movement in fluid media. However, theoretically, land animals should travel at their maximum speed to minimize COT, which they do not, instead travelling at walking pace. We measured oxygen consumption in humans to demonstrate that the energetic costs of turning increase disproportionately with both speed and angular velocity. This resulted in the minimum COT speed occurring at very low speeds, which reduced with increased path tortuosity. Data on turn rates from six free-ranging terrestrial species underpinned this because all individuals turned faster at the slowest speeds across the full speed range. The optimum movement speed for minimum COT in land animals thus depends on the environment and behavior since both affect track tortuosity.

ecology↗