Sha B F, England S J, Parisi R A, Strobel R J
Department of Medicine, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, New Brunswick, NJ 08903, USA.
J Appl Physiol (1985). 2000 May;88(5):1678-84. doi: 10.1152/jappl.2000.88.5.1678.
Resting muscle length affects both maximum force production and force maintenance. The strength and force maintenance characteristics of the genioglossus as a function of resting muscle length have not been described. We hypothesized that genioglossus optimum length (L(o)) could be defined in vivo and that the ability of the genioglossus to sustain a given workload would decrease as resting length deviated from L(o). To test this, 11 normal men repeated maximal isometric genioglossus protrusions at different muscle lengths to determine L(o). L(o) was also obtained by using submaximal efforts while simultaneously recording electromyographic activity of the genioglossus, with L(o) defined as the length at which the force-to-genioglossus electromyographic activity ratio was maximum. Both methods provided similar results. Force maintenance was measured at four muscle lengths on separate days. Target efforts representing 60% of each subject's maximum at L(o) and lasting 5 s were performed at 12-s intervals. Time limit of endurance of the genioglossus was defined as the time from trial onset at which 90% of the target could not be maintained for three consecutive efforts. Time limit of endurance was greatest at L(o) and fell to 47.5% at L(o) + 1 cm, 53.8% at L(o) - 1 cm, and 47.4% at L(o) - 1.5 cm. We conclude that L(o) of the genioglossus can be determined in vivo and that force maintenance of the genioglossus is decreased when operating length deviates from L(o).
静息肌肉长度会影响最大力量产生和力量维持。舌颏肌作为静息肌肉长度的函数的强度和力量维持特性尚未被描述。我们假设舌颏肌的最佳长度（L(o)）可以在体内确定，并且当静息长度偏离L(o)时，舌颏肌维持给定工作量的能力会下降。为了验证这一点，11名正常男性在不同肌肉长度下重复进行最大等长舌颏肌前突动作以确定L(o)。还通过次最大努力同时记录舌颏肌的肌电图活动来获得L(o)，L(o)被定义为力量与舌颏肌肌电图活动比值最大时的长度。两种方法得出了相似的结果。在不同日期的四个肌肉长度下测量力量维持情况。以代表每个受试者在L(o)时最大力量的60%且持续5秒的目标努力，每隔12秒进行一次。舌颏肌耐力的时间限制被定义为从试验开始起，目标力量的90%无法在连续三次努力中维持的时间。耐力时间限制在L(o)时最大，在L(o)+1厘米时降至47.5%，在L(o)-1厘米时降至53.8%，在L(o)-1.5厘米时降至47.4%。我们得出结论，舌颏肌的L(o)可以在体内确定，并且当工作长度偏离L(o)时，舌颏肌的力量维持会下降。
