Abstract
BackgroundVagal withdrawal forms the dominant mechanism determining the rapid heart rate (HR) response at the onset of moderate intensity isometric handgrip (IHG) exercise. Previous evidence suggested that the addition of submotor somatosensory stimulation (STIM) can elevate vagal cardiac function in some individuals. This study tested the hypothesis that STIM can interfere with the vagal withdrawal and HR responses at the exercise onset.MethodsYoung healthy individuals (n=7, ages 24 ± 1.2 years) were recruited. STIM was provided by transcutaneous electrical nerve stimulation (TENS; 100 Hz, 50 μs) on the medial forearm through anesthetized skin. A 3‐lead ECG provided R‐R interval data. Participants performed 2–3 trials of IHG at 35–40% maximal voluntary contraction, each lasting 20 seconds and separated by one minute of rest. These were performed both with and without STIM and baseline cardiovagal influence was modified by repeating the tests in seated and supine positions using a varied order of STIM delivery.ResultsIHG elicited increased HR in each posture (supine: baseline=64 ± 9 bpm, IHG=73 ± 7 bpm; p<0.05; seated: baseline=66 ± 6 bpm, IHG=78 ± 8 bpm, p<0.05). In the seated position, STIM reduced the maximum HR response to IHG, compared to no STIM, in five out of seven participants resulting in an overall modest effect (no STIM: 19 ± 10 bpm; STIM: 15 ± 8 bpm; p<0.05; d=0.44). In the supine position, however, the effect of STIM to reduce the HR response was observed in only three out of seven participants. Thus, there was no significant difference between treatments (no STIM: 15 ± 7 bpm; STIM: 16 ± 9 bpm; p>0.05; d=0.12).ConclusionThese data suggests that the HR response to exercise in young healthy adults can be modulated with submotor somatosensory nerve stimulation but that this effect is most apparent in the seated position.Support or Funding InformationSupported by Natural Sciences and Engineering Research Council of CanadaThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
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