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RESEARCH PRODUCT

Effect of gender and obesity on electrical current thresholds

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Introduction: In this study we investigated the influence of gender and obesity on electrical current thresholds in an attempt to optimize the application of skeletal muscle electrical stimulation (ES) in clinical practice. Methods: Thirty- two obese and 35 age-matched, non-obese men and women received graded ES to the quadriceps muscle for sensory (detection) and motor (contraction) threshold assessment. Con- comitant pain and tolerance to ES were recorded. Results: Sen- sory threshold was lower in women than in men (P < 0.001), both obese and non-obese. Sensory and motor thresholds were higher in obese than in non-obese subjects (P < 0.05), and body mass index was a strong predictor of motor excitabil- ity (r 2 ¼ 0.56-0.61). Current tolerance to motor stimulation was reduced in obese individuals, particularly in women, whereas pain was not influenced by gender or obesity. Conclusions: We suggest that both gender and obesity factors should be care- fully considered in the design of rational ES treatments. Muscle Nerve 000: 000-000, 2011 Electrical stimulation (ES) of skeletal muscles is largely adopted in clinical settings for preserving or improving muscle function (motor stimulation, better known as neuromuscular electrical stimula- tion), 1 and for relieving pain (sensory level stimu- lation, better known as transcutaneous electrical nerve stimulation). 2 Stimulation parameters of fre- quency, pulse duration, and amplitude correlate with the characteristics of the depolarized nerve fiber. In particular, the relationship between stimu- lus pulse amplitude and pulse duration can be illustrated on a strength-duration curve, 3 where thresholds for sensory and motor responses decrease exponentially with increasing pulse durations.