This study examined the ability of human subjects to match a force in their quadriceps muscle during fatigue. Twenty subjects (mean age: 23.4 yrs, mean height: 167.8 cm, mean weight, 62.6 kg) were enrolled in the experiment. In the force-matching task, the quadriceps muscle generated 50% of the MVIC (maximum voluntary isometric contraction) torque under visual control and then without visual feedback. After inducing fatigue in the quadriceps muscle, the subjects were required to match 50% of the MVIC torque without visual feedback. The perceived magnitude of the force and force-matching errors were measured. 50% of the MVIC torque was perceived from 39.96 Nm in the pre-fatigue condition to 44.95 Nm in the post-fatigue condition. 50% of the MVIC torque-matching errors increased significantly from .55% in the pre-fatigue condition to 9.6% in the post-fatigue condition (p<.001). in addition, there were significantly more force-matching errors in women than in men (p<.01). In conclusion muscle fatigue can interfere with a subject's ability to match a force. This suggests that muscle fatigue may contributes to the sensitization of the proprioception.

The purpose of this study was to evaluate the effect of concurrent and reciprocal isometric contraction and angle of ankle joint on fatigue of concentrically contracting contralateral dorsiflexor and plantar flexor. Seventeen able-bodied subjects participated in the study. Concurrent and reciprocal isometric contraction were performed under three different ankle joint angles (dorsiflexion, neutral position, plantar flexion). During concurrent or reciprocal isometric contraction. fatigue of concentrically contracting contralateral tibialis anterior, gastrocnemius, and soleus was investigated and compared. There was no interaction between different ankle joint angles and direction of isometric contraction (p<.05). No significant differences were found among three different ankle joint angles (p<.05). Contralateral muscle fatigability was lower in reciprocal isometric contraction than that in concurrent isometric contraction (p<.05). Therefore, the findings of this study suggest that reciprocal isometric contraction is more beneficial than concurrent isometric contraction inducing less fatigability during contralateral concentric contraction.

본 연구는 상지운동 동안에 복부에 적용된 압력이 요부와 복부의 근피로도에 미치는 영향을 알아보았다. 연구대상자는 성인 남자 5명이었다. 연구대상자가 10 repetitions maximun (RM) 무게의 아령을 이용하여 1분 동안 상지운동을 수행 시 0 mmHg, 저압(30 mmHg), 중압(70 mmHg), 고압(100 mmHg)의 외부 압력이 복부에 적용되었고, 복직근, 외복사근, 내복사근, 척추기립근에서 근전도 자료가 수집되었다. 주파수 분석을

The purpose of this study was to assess the fatigue in lumbar and abdominal muscles in patients with chronic low back pain compared with normal subjects using spectral analysis with mean power frequency and median power frequency. The experimental group consisted of twenty subjects who had experienced chronic low back pain for over one year after the onset day. A control group consisted of twenty normal subjects with no history of low back pain. All subjects stood in an apparatus to perform sustained contraction in the lumbar and abdominal muscles for 30 seconds with 60% maximal voluntary isometric contraction (MVIC). The resulting electromyographic (EMG) recorded time serial data were transformed into frequency serial data by Fast Fourier Transformation (FFT). The results were as follows: 1) lumbar muscles measured, the frequency change ratio of both median power frequency and mean power frequency was significantly greater for experimental group compared with control group group (p<0.05). In measured two abdominal muscles (inferior rectus abdominis, obliquus externus abdominis) except superior rectus abdominis, the frequency change ratio of both median power frequency and mean power frequency was significantly greater for experimental group compared with control group (p<0.05). 2) In all three (longissimus thoracis, iliocostalis lumborum, multifidus) lumbar muscles measured, the initial frequency value of both median power frequency and mean power frequency was significantly lower for the experimental group compared with the control group (p<0.05). In the two (inferior rectus abdominis, obliquus externus abdominis) abdominal muscles measured (superior rectus abdominis not included), the initial frequency value of both median power frequency and mean power frequency was significantly lower for the experimental group compared with the control group (p<0.05). These results suggest that in patients with chronic low back pain there is a trend for more fatigue to occur in both lumbar and abdominal muscles than in the normal control group. This would seem to suggest that in treatment programs for patients with chronic low back pain, improvement of endurance in all trunk muscles should be considered.

Astragalus membranaceus is a well known oriental medicinal herb. The polysaccharides of the aboveground parts (AMA) and the radix (AMR) of A. membranaceus are the most important functional constituents. Methods and Results: The aim of this study was to determine the effects of AMA and AMR on the oxidative damage induced in the skeletal muscle of rats subjected to exhaustive exercise. Sprague-Dawley rats were randomly divided into exercise and non-exercise groups; in the groups receiving the test compounds, AMA and AMR were administered orally for 30 days. Skeletal muscle samples were collected from each rat after running to exhaustion on a treadmill to determine the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) and the concentation of malondialdehyde (MDA). The antioxidant enzyme activities of SOD and GSH-Px of skeletal muscle of AMA- and AMR-treated groups were significantly higher than those of the control and commercial sports drink (SPD)-treated groups in exhaustive exercise rats. In addition, MDA concentrations in the skeletal muscle of the AMA- and AMR-treated groups were significantly lower than those of the control and SPD-treated groups. In the present study, the effects of AMA and AMR on exercise endurance capacity were also evaluated in mice subjected to a swimming exercise test. AMA and AMR supplementation prolonged the swimming time of mice and enhanced exercise endurance capacity. AMA and AMR possess the ability to retard and lower the production of blood lactate, and prevent the decrease of serum blood glucose. Conclusions: These results showed that, AMR and AMA exerted beneficial effect in mice, increasing the activity of the antioxidant systems and inhibiting oxidative stress induced by exhaustive exercise. The compounds improved exercise performance and showed anti-fatigue effects against exhaustive exercise.