Abstract
This study investigated the effects of eccentric (ECC) and concentric (CON) semi-recumbent leg cycling on global corticospinal excitability (CSE), assessed through the activity of a non-exercised hand muscle. Thirteen healthy male adults completed two 30-min bouts of moderate intensity ECC and CON recumbent cycling on separate days. Power output (POutput), heart rate (HR) and cadence were monitored during cycling. Global CSE was assessed using transcranial magnetic stimulation to elicit motor-evoked potentials (MEP) in the right first dorsal interosseous muscle before (‘Pre’), interleaved (at 10 and 20 mins, t10 and t20, respectively), immediately after (post, P0), and 30-min post exercise (P30). Participants briefly stopped pedalling (no more than 60 s) while stimulation was applied at the t10 and t20 time-points of cycling. Mean POutput, and rate of perceived exertion (RPE) did not differ between ECC and CON cycling and HR was significantly lower during ECC cycling (P = 0.01). Group mean MEP amplitudes were not significantly different between ECC and CON cycling at P0, t10, t20, and P30 and CON (at P > 0.05). Individual participant ratios of POutput and MEP amplitude showed large variability across the two modes of cycling, as did changes in slope of stimulus-response curves. These results suggest that compared to ‘Pre’ values, group mean CSE is not significantly affected by low-moderate intensity leg cycling in both modes. However, POutput and CSE show wide inter-participant variability which has implications for individual neural responses to CON and ECC cycling and rates of adaptation to a novel (ECC) mode. The study of CSE should therefore be analysed for each participant individually in relation to relevant physiological variables and account for familiarisation to semi-recumbent ECC leg cycling.
Highlights
Www.nature.com/scientificreports results suggest a neural coupling between the upper and lower limbs
Even though the range of mean Power output (POutput) was smaller at 10, 20, and P0 and for the entire bout for ECC compared to CON cycling at a set cadence of 60 rpm, participants showed higher power profiles in CON or ECC conditions
Our findings show that group mean global corticospinal excitability (CSE) as measured in the non-exercised muscle was not statistically different when interleaved and after low-intensity semi-recumbent ECC and CON leg cycling compared to ‘Pre’ exercise values
Summary
Www.nature.com/scientificreports results suggest a neural coupling between the upper and lower limbs. What evidence is there that ECC cycling would result in quantitatively different measures of global CSE during or after cycling, compared to CON cycling?4 quantified global CSE (input-output curves of MEPs) using a non-exercised hand muscle before, immediately after and 30 min post CON cycling in a recumbent position They measured short and long intracortical inhibition (SICI and LICI, respectively) and intracortical facilitation (ICF). They found no differences in CSE at different stimulus intensities before, immediately after or 30 min post exercise, they did find that CON cycling for 20 min led to increased ICF and decreased SICI Their results contrast somewhat with those of[8] who recorded greater global CSE in non-exercised muscles after regular CON leg cycling than static contractions of the same muscles as those used during cycling. Semi-recumbent CON cycling would show facilitation of CSE, whereas semi-recumbent ECC cycling (associated with spinal inhibition) would not show such facilitation
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