Bonardi, A. | bioRxiv Science

bioRxiv2024

E-bike riding: A metabolic evaluation in the context of exercise intensity domains

IntroductionE-bikes are being promoted as a mode of transportation that can aid with meeting current physical activity guidelines. This study evaluated exertional intensity associated with E-Biking within the exercise intensity domain framework. We hypothesized that exertional intensity of E-bikes is insufficient to evoke a metabolic demand associated with the minimum intensity needed to improve cardiorespiratory fitness. MethodsForty-four participants (22 females) of varying activity levels completed two experimental sessions. The first session involved a lab-based ramp-incremental exercise test to determine [V]O2max, gas exchange threshold (GET), and respiratory compensation point (RCP). The second session involved the completion of two outdoor rides on the same bike equipped with an electrical motor E-bike. The first ride was completed without electrical assistance, while the second was. The power output (PO) and speed were set at an intensity corresponding to [~]10% above GET. ResultsAs expected, using E-bike assistance resulted in a lower metabolic demand, falling well below GET. While the absolute power output (PO) was different between sexes, relative heart rate (HR) and relative PO were similar between the rides without and with assistance. This suggests that when riding an E-bike, the internal load is similar between sexes. ConclusionDespite E-bikes facilitate a more active lifestyle and help to reduce the emission of pollutants, when interpreted within the context of the exercise intensity domain schema, their associated exertional intensity is likely insufficient to confidently elicit cardiorespiratory benefits.

physiology↗

bioRxiv2023

The short-term acquisition of a skill learning task unveils the neural filtering of shared synaptic input to spinal motor neurons

The acquisition of a motor skill involves adaptations of spinal and supraspinal pathways to alpha motoneurons. In this study, we estimated the shared synaptic contributions of these pathways to understand the neural mechanisms underlying the short-term acquisition of a new force-matching task. High-density surface electromyography (HDsEMG) was acquired from the first dorsal interosseous (FDI; 7 males and 6 females) and tibialis anterior (TA; 7 males and 4 females) during 15 trials of an isometric force-matching task. For two selected trials (pre- and post-skill acquisition), we decomposed the HDsEMG into motor unit spike trains, tracked motor units between trials, and calculated the mean discharge rate and the coefficient of variation of inter-spike interval (CoVISI). We also quantified the post/pre ratio of motor units coherence within delta, alpha, and beta bands. Improvements in force-matching were accompanied by a significant increase in the mean discharge rate and a decrease in CoVISI for both muscles. Moreover, the area under the curve within alpha band decreased by [~]22% and [~]13% for the TA and FDI muscles, respectively, with no changes in the delta or beta bands. These reductions correlated significantly with increased coupling between force/neural drive and target oscillations. These results suggest that the short-term acquisition of a new force-matching skill is mediated by the attenuation of tremor oscillations in the shared synaptic inputs. In other words, the central nervous system acts as a matched filter to modulate the synaptic weights of shared inputs and suppress neural components unrelated to the specific task. Supported by simulations, a plausible mechanism behind these alpha band reductions may involve spinal interneurons phase-cancelling descending oscillations.

neuroscience↗