TY - JOUR
T1 - Role of sarcolemma action potentials and excitability in muscle fatigue
AU - Balog, E. M.
AU - Thompson, L. V.
AU - Fitts, R. H.
PY - 1994
Y1 - 1994
N2 - The purposes of this study were to characterize the alterations in the sarcolemma action potential (AP) waveform and sarcolemma excitability as a result of fatiguing stimulation of the frog semitendinosus muscle and to relate these changes to the decrease in the force-generating ability of the muscle. Trains of APs were recorded before and after stimulation (100-ms trains, 150 Hz, 1/s for 5 min). The resting membrane potential (RMP), AP overshoot (OS), and duration at 50% of peak magnitude (DUR) were 84.3 ± 2.0 mV, 19.5 ± 1.9 mV, and 1.3 ± 0.1 ms, respectively, before stimulation. The stimulation protocol caused RMP to depolarize to -75.1 ± 2.0 mV, OS to fall to 7.3 ± 1.9 mV, and DUR to increase to 2.5 ± 0.4 ms. RMP and OS recovered fully in 5 min after the cessation of stimulation, whereas DUR was still prolonged. Before the stimulation protocol, AP frequency matched the stimulation frequency at all stimulation rates ≤150 Hz. At 200-Hz stimulation, AP frequency was 192 ± 6 Hz. After 5 min of stimulation, AP frequency matched the stimulation frequency only at ≤60 Hz. At 100-, 150-, and 200-Hz stimulation, AP frequencies were 89 ± 8, 84 ± 17, and 79 ± 15 Hz, respectively. Because of a decreased fusion frequency at fatigue, the fall in the sarcolemma AP frequency did not contribute to the decreased force. The stimulation-induced alterations in the AP waveform were moderate and unlikely to have caused fatigue. However, the alterations in AP may have been more extreme in the depths of the transverse tubules.
AB - The purposes of this study were to characterize the alterations in the sarcolemma action potential (AP) waveform and sarcolemma excitability as a result of fatiguing stimulation of the frog semitendinosus muscle and to relate these changes to the decrease in the force-generating ability of the muscle. Trains of APs were recorded before and after stimulation (100-ms trains, 150 Hz, 1/s for 5 min). The resting membrane potential (RMP), AP overshoot (OS), and duration at 50% of peak magnitude (DUR) were 84.3 ± 2.0 mV, 19.5 ± 1.9 mV, and 1.3 ± 0.1 ms, respectively, before stimulation. The stimulation protocol caused RMP to depolarize to -75.1 ± 2.0 mV, OS to fall to 7.3 ± 1.9 mV, and DUR to increase to 2.5 ± 0.4 ms. RMP and OS recovered fully in 5 min after the cessation of stimulation, whereas DUR was still prolonged. Before the stimulation protocol, AP frequency matched the stimulation frequency at all stimulation rates ≤150 Hz. At 200-Hz stimulation, AP frequency was 192 ± 6 Hz. After 5 min of stimulation, AP frequency matched the stimulation frequency only at ≤60 Hz. At 100-, 150-, and 200-Hz stimulation, AP frequencies were 89 ± 8, 84 ± 17, and 79 ± 15 Hz, respectively. Because of a decreased fusion frequency at fatigue, the fall in the sarcolemma AP frequency did not contribute to the decreased force. The stimulation-induced alterations in the AP waveform were moderate and unlikely to have caused fatigue. However, the alterations in AP may have been more extreme in the depths of the transverse tubules.
KW - excitation-contraction coupling
KW - frog semitendinosus
KW - microelectrodes
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U2 - 10.1152/jappl.1994.76.5.2157
DO - 10.1152/jappl.1994.76.5.2157
M3 - Article
C2 - 8063681
AN - SCOPUS:0028305080
SN - 8750-7587
VL - 76
SP - 2157
EP - 2162
JO - Journal of applied physiology
JF - Journal of applied physiology
IS - 5
ER -