Prediction of calf volume during muscle contraction

This study evaluated the relationship between calf volume changes and different intensities of maximum voluntary contractions (MVCs) of a lower limb performing plantar flexions. An electronic plethysmography instrument (EPI) was developed, and after testing for its reliability, it was used to measure calf volume changes. For EPI, the reliability correlation coefficients (r) to measure calf volume consistently were .98, .91, and .98 at 100% MVC, 80% MVC, and 60% MVC, respectively. There were also significant correlations between calf volume changes and the different intensities of MVC (MVC: r = .42, p < .011; 80% MVC: r = .41, p < .013; 60% MVC: r = .5, p < .002). The calf volume changes at different levels of muscle contractions also correlate significantly (upper calf: r = .55, p < .0002; middle calf: r = .58, p < .0007; and lower calf: r = .55, p < .002). The results indicated that EPI might be used as a reliable tool to predict the intensity of muscle contraction based on calf volume changes. Clinicians who use functional electrical stimulation to induce muscle contraction in people with muscle paralysis may use EPI to predict the volume changes during functional electrical stimulation-induced contractions and to deliver the proper amount of electrical stimulation, producing the desired level of contraction without undue stimulation or fatigue.