Metabolic costs of force generation for constant‐frequency and catchlike‐inducing electrical stimulation in human tibialis anterior muscle

Metabolic costs of force generation were compared for constant‐frequency and catchlike‐inducing electrical stimulation. Repetitive catchlike‐inducing trains consisted of 2 interpulse intervals (IPIs) at 12.5 ms, 1 IPI at 25 ms, and 5 IPIs at 50 ms. Constant‐frequency trains consisted of 8 IPIs at 37.5 ms. One train was delivered to the peroneal nerve every 2.5 s for 36 times under ischemic conditions. Anaerobic adenosine triphosphate (ATP) turnover was determined using 31‐phosphorus magnetic resonance spectroscopy (P‐MRS) of the human tibialis anterior muscle. Compared with constant‐frequency trains, catchlike‐inducing trains produced a faster force generation and were more effective in maintaining the force–time integral as well as peak force. However, ATP costs of force generation were similar for the catchlike‐inducing and constant‐frequency stimulation (6.7 ± 1.1 and 6.6 ± 1.0 μmol ATP/kg wet weight/N·s, respectively, P = 0.601). This suggests that the positive effects of catchlike‐inducing stimulation on force maintenance are mediated by potentiated Ca 2+ release from the sarcoplasmic reticulum rather than by lower metabolic costs of muscle force generation. Our findings also suggest that catchlike‐inducing stimulation produces larger forces in fatigued muscle than constant‐frequency trains and thus may be beneficial for muscle training or rehabilitation when muscle loading needs to be maintained in repetitive contractions. © 2002 Wiley Periodicals, Inc. Muscle Nerve 25: 000–000, 2002