Modulation of subjective peripheral sensation, F-waves, and somatosensory evoked potentials in response to unilateral pinch task measured on the contractile and non-contractile sides.

Depression of the sensory input during voluntary muscle contractions has been demonstrated using electrophysiological methods in both animals and humans. However, the association between electrophysiological responses of the sensory system and subjective peripheral sensation (SPS) during a voluntary muscle contraction remains unclear. This study aimed to describe the changes in SPS, spinal α-motoneuron excitability (F-wave to M-wave amplitude), and somatosensory evoked potentials (SEPs) during a unilateral pinch-grip task. Outcome variables were measured on the side ipsilateral and contralateral to the muscle contraction and at rest (control). Participants were 8 healthy men aged 20.9±0.8 years. The isometric pinch-grip task was performed at 30% of the maximum voluntary isometric force measured for the right and left hands separately. The appearance rate of the F-wave during the task was significantly higher for the ipsilateral (right) hand than for the contralateral (left) hand and control condition. Although there was no difference in the F-wave latency between hands and the control condition, the amplitude of the F-wave was significantly higher for the ipsilateral (right) hand than for the contralateral (left) hand and the control condition. There was no difference in the amplitude of the SEP at N20. However, the amplitude at P25 was significantly lower for the ipsilateral (right) hand than for the contralateral (left) hand and the control condition. The accuracy rate of detecting tactile stimulation, evaluated for 20 repetitions using a Semmes-Weinstein monofilament at the sensory threshold for each participant, was significantly lower during the pinch-grip task for both the ipsilateral (right) and contralateral (left) hands than in the control condition. Overall, our findings show that SPS and neurophysiological parameters were not modulated in parallel during the task, with changes in the subjective sensation preceding changes in electrophysiological indices during the motor task. Our findings provide basic information on sensory-motor coordination.

Equol-producing status affects exercise training-induced improvement in arterial compliance in postmenopausal women.

Central arterial compliance decreases drastically after menopause. Regular intake of soy isoflavone and aerobic exercise increase arterial compliance. The equol is a metabolite of isoflavone daidzein by gut microbiome. We determined whether the equol-producing status affects aerobic exercise-induced improvement in carotid arterial compliance. Forty-three postmenopausal women were assigned to two intervention groups: 1) exercise and isoflavone (Ex+Iso, n = 27 females) or 2) isoflavone interventions (Iso; n = 16 females). Participants of the Ex+Iso intervention group completed an 8-wk aerobic exercise training, and all participants were administered with oral isoflavone supplements during the interventions. The equol-producing status (equol producers or nonproducers) was determined from urine equol concentrations after a soy challenge. In the Ex+Iso intervention group, carotid arterial compliance increased in the equol producers (0.084 ± 0.030→0.117 ± 0.035 mm2/mmHg), but not in the nonproducers (0.089 ± 0.028→0.097 ± 0.026 mm2/mmHg) after the intervention (interaction effect; P < 0.05). The magnitude of increases in carotid arterial compliance was significantly greater in the equol producers than in the non-equol producers (P < 0.05). In the isoflavone intervention group, there were no changes in any parameters after the intervention irrespective of the equol status. These results suggest that equol-producing status is obligatory to aerobic exercise training-induced improvements in central arterial compliance in postmenopausal women.NEW & NOTEWORTHY Isoflavone intake and aerobic exercise increase central artery compliance. Equol, a metabolite of isoflavone daidzein by gut microbiome, has beneficial effects on vascular function. We demonstrated for the first time that the interaction of aerobic exercise and equol production status plays an essential role in improvements in central artery compliance in postmenopausal women. More specifically, the equol-producing status was obligatory to exercise training-induced improvements in central arterial compliance in postmenopausal women.

Sensory gating and suppression of subjective peripheral sensations during voluntary muscle contraction.

BACKGROUND: During voluntary muscle contraction, sensory information induced by electrostimulation of the nerves supplying the contracting muscle is inhibited and the somatosensory evoked potentials (SEPs) amplitude decreases. This depression of sensory input during voluntary muscle contraction has been demonstrated by many studies using electrophysiological methods. However, the association between the electrophysiological response of the sensory system during sustained muscle contraction and subjective peripheral sensation (SPS) is still unclear. The aim of this study was to investigate changes in spinal excitability, SEPs, and SPS during voluntary muscle contraction. RESULTS: The appearance rate of the F-wave was significantly higher during muscle contraction than rest, whereas no significant difference was observed in F-wave latency between muscle contraction and rest. Furthermore, the P25 amplitude of SEPs was significantly lower during muscle contraction than rest, whereas the N20 amplitude of SEPs exhibited no significant differences. The SPS was significantly lower during muscle contraction than rest CONCLUSIONS: We conclude that sensory gating, which is found in the P25 component of SEPs during muscle contraction, is one of the neurophysiological mechanisms underlying the suppression of SPS.

Effect of circulatory system response to motor control in one-sided contractions.

PURPOSE: The purpose of this study was to clarify the effect one-sided skeletal muscle contraction has on the circulatory system, spinal α-motoneuron excitability, and somatosensory-system-evoked potential. METHOD: Nine healthy males maintained tension at 10, 20, and 30% of maximal voluntary contraction in static gripping in right hand. Heart rate, ln high frequency (HF), blood pressure (BP), F-wave, and somatosensory-evoked potential (SEP) were recorded during gripping task. BP, F-wave and SEP were recorded from left hand (contralateral side from contracting side). RESULT AND CONCLUSION: There were significant main effects of contractions strength on heart rate (0%: 68.2 ± 6.8 bpm, 10%: 67.6 ± 7.4 bpm, 20%: 69.7 ± 8.5 bpm, 30%: 73.7 ± 9.3 bpm, F3.24=9.18, P < 0.01), systolic BP (0%: 127.7 ± 15 mmHg, 10%: 136.2 ± 13.5 mmHg, 20%: 136.2 ± 13.5 mmHg, 30%: 140.0 ± 17.1 mmHg, F3.24=23.93, P < 0.01), diastolic BP (0%: 69.3 ± 8.5 mmHg, 10%: 76.9 ± 11.1 mmHg, 20%: 79.9 ± 12.5 mmHg, 30%: 86.2 ± 14 mmHg, F3.24=17.09, P < 0.01), and F-wave appearance rate (0%: 29.7 ± 15.6%, 10%: 39.3 ± 20.5%, 20%: 47.5 ± 22.9%, 30%: 55.2 ± 21.8%, F3.24=14.04, P < 0.01). For the ln HF (0%: 5.9 ± 0.6, 10%: 6.3 ± 0.9, 20%: 6.3 ± 1.3, 30%: 6.0 ± 1.0, F3.24=2.43, P = 0.08), F-wave latency (0%: 29.6 ± 1.7 ms, 10%: 26.9 ± 2.1 ms, 20%: 26.5 ± 3.6 ms, 30%: 26.9 ± 2.3 ms, F3.24=0.11, P = 0.96), F-wave amplitude (0%: 2.0 ± 0.9%, 10%: 2.2 ± 0.9%, 20%: 2.3 ± 0.7%, 30%: 2.8 ± 1.1%, F3.24=2.80, P = 0.06), and N20 amplitude (0%: 3.9 ± 1.7 µV, 10%: 3.7 ± 1.7 µV, 20%: 3.9 ± 1.7 µV, 30%: 3.9 ± 1.8 µV, F3.24=0.61, P = 0.62), between the conditions. We conclude that regulation of the circulatory system and motor system has a limited effect on sensory input.