• 한국전문물리치료학회지
• /
• 제25권4호
• /
• pp.46-52
• /
• 2018

Background: The hamstring muscles in the lower extremity are highly important for knee joint stability and can be classified into medial and lateral hamstrings according to the anatomical position, which have some different functions. To measure the strength of the individual hamstring muscles, manual muscle testing is clinically performed by dividing rotation postures into internal and external postures. However, this has no sufficient scientific background. Objects: This study aimed to test the difference that the tibial rotation would cause in the muscle activity of the medial and lateral hamstrings. Methods: The muscle activities of the biceps femoris, semitendinosus, and semimembranosus were measured in a total of three different postures (neutral position and internal and external rotations) with 3 replications. During the maximal isometric contraction, resistance was constantly provided by the string attached to the strap, not by manual resistance of the examiner. Before and after electromyography measurements, the participants underwent hamstring flexibility measurement using the active knee extension test in the supine position on the treatment table. Results: The semitendinosus had a 12.56% reduction in muscle activity in external rotation as compared with that in neutral position. The biceps femoris and semimembranosus showed reduced muscle activities in both external and internal rotations as compared with those in neutral position. Only the women showed significant decreases in the comparison between pre and post-active knee extension. Conclusion: Only the semitendinosus muscle was consistent with the anatomical speculation. However, the reduction in the muscle activity of the semitendinosus as compared with that in neutral position was only 12.56%, the clinical value of which may be difficult to justify.

• 한국운동역학회지
• /
• 제31권2호
• /
• pp.140-147
• /
• 2021

Objective: The purpose of this study is to identify the mechanism of changes in maximum voluntary torque with the magnitude and duration of pre-activation torque during voluntary isometric knee extension. Method: 11 male subjects (age: 25.91±2.43 yrs., height: 173.12±3.51 cm, weight: 76.45±7.74 kg) participated in this study. The subjects were required to produce maximal voluntary isometric torque with a particular pre-activation torque condition. The properties of pre-activation torque consisted of the combinations of 1) three levels of magnitude, e.g., 32 Nm, 64 Nm, 96 Nm, and 2) two levels of duration, e.g., 1 sec, and 3 sec; thus, a total of six conditions were given to the subjects. The force and EMG data were measured using the force transducers and wireless EMG sensor, respectively. Results: The results showed that the maximum voluntary torque increased the most with relatively large and fast (96 Nm, 1 sec) pre-activation condition. Similarly, with relatively large and fast (96 Nm, 1 sec) preactivation, it was found that the integrated EMG (iEMG) of the agonist muscles increased, while no significant changes in the co-contraction of the antagonist muscles for the knee extension. Also, the effect of pre-activation conditions on the rate of torque development was not statistically significant. Conclusion: The current findings suggest that relatively larger in magnitude and shorter in duration as the properties of pre-activation lead to a larger magnitude of maximal voluntary torque, possibly due to the increased activity of the agonist muscles during knee extension.

• 한국전문물리치료학회지
• /
• 제10권3호
• /
• pp.141-149
• /
• 2003

Median frequency can be regarded as a valid indicator of local muscle fatigue. As local muscle fatigue develops, the muscle fiber conduction velocity decreases, the fast twitch fibers are recruited less, and consequently the median frequency shifts toward the lower frequency area. The aim of this study was to test the characteristics of the median frequency according to exercise load (30% and 60% of MVC on the biceps brachii, 40% and 80% of MVC on the vastus lateralis) during the fatiguing isometric exercise. Thirteen healthy male volunteer students of Yonsei University were recruited. After the testing maximal voluntary isometric contraction, three variables (initial median frequency, regression slope, fatigue index) from the regression line of MDF data were measured in each exercise load. The results showed that the regression slope and fatigue index were significantly different for the biceps brachii, but not for the vastus lateralis initial MDF was not significant difference according to the exercise load on both muscles. The regression slope and fatigue index could monitor physiologic muscle change during fatiguing isometric exercise. The results showed that two MDF variables reflect the local muscle fatigue according to the exercise load.

• International Journal of Contents
• /
• 제5권4호
• /
• pp.35-39
• /
• 2009

The purpose of this study was to evaluate the changes in skeletal muscle architecture and qualitative properties by muscle contraction force when neuromuscular electrical stimulation (NMES) of 50% MVIC was applied. Sixteen subjects (8 male, 8 female) without neuromuscular disease volunteered to participate in the study. All subjects were divided into two subgroups: control (no electrical stimulation) group and 50% maximal voluntary isometric contraction (MVIC) group. NMES training program was performed in the calf muscle three times a week for 10 weeks. Before and after the experiments, the MVIC of ankle plantar flexor was measured by the use of dynamometer, and the ultrasonography in the gastrocnemius medialis muscle was measured. The following results were obtained; MVIC was significantly increased in the electrical stimulation groups. Pennation angle, muscle density, and white area index also considerably changed in the electrical stimulation groups. In conclusion, the NMES training of 50% MVIC, comparative low level, improved the skeletal muscle architecture and the qualitative properties as well as the muscle contraction force.

• 대한산업공학회지
• /
• 제25권3호
• /
• pp.330-335
• /
• 1999

The goal of the study is to determine the most sensitive parameter to represent the degree of muscle force and fatigue. Various numerical parameters such as the first coefficient of Autoregressive (AR) Model, Root Mean Square (RMS), Zero Crossing Rate (ZCR), Mean Power Frequency (MPF), Median Frequency (MF) were tested in this study. Ten healthy male subjects participated in the experiment. They were asked to extend their trunk by using the right and left erector spinae muscles during a sustained isometric contraction for twenty seconds. The force levels were 15%, 30%, 45%, 60%, and 75% of Maximal Voluntary Contraction (MVC), and the order of trials was randomized. The results showed that RMS was the best parameter to measure the force level of the muscle, and that the first coefficient of AR model was relatively sensitive parameter for the fatigue measurement at less than 60% MVC condition. At the 75% MVC, however, both MPF and the first coefficient of AR Model showed the best performance in quantification of muscle fatigue. Therefore, the sensitivity of measurement can be improved by properly selecting the parameter based upon the level of force during a sustained isometric condition.

• 한국전문물리치료학회지
• /
• 제20권2호
• /
• pp.1-10
• /
• 2013

The purpose of this study was to determine the effect of the changes that occur in the leg muscle activity of unstable surface with different levels of air pressures. Three groups of college students have been placed randomly on unstable surfaces with different air pressures at group 1.0 psi ($n_1$=36), group 1.4 psi ($n_2$=40), and group 1.8 psi ($n_3$=40). Using surface electromyography, the recruitment of the tibialis anterior, peroneus longus, and the gastrocnemius was measured. Maximal voluntary isometric contraction was measured at the different air pressures based on the manual muscle test, then normalizing the value to %maximal voluntary isometric contraction (%MVIC). The tibialis anterior muscle activity was significant change from the unstable surface with difference levels of air pressures between group 1.0 psi and 1.8 psi and between group 1.4 psi and 1.8 psi. peroneus longus muscle activity was significant changes in muscle activity occurred between 1.0 psi and 1.4 psi group and between 1.0 psi and 1.8 psi group. Gastrocnemius muscle activity was significant change in muscle activity occurred between 1.0 psi and 1.4 psi group and between 1.0 psi and 1.8 psi group. In conclusion it identify that 1.0 psi group is most effective on muscle activity than the other groups. These suggest that the rehabilitation or strengthening of patients with ankle injuries, balance exercise with low air pressure like 1.0 psi can be more effective.

• 한국전자통신학회논문지
• /
• 제8권8호
• /
• pp.1271-1276
• /
• 2013

본 연구는 넙다리곧은근에 적용한 정적 및 탄성적 스트레칭의 유지기간을 알아보기 위하여 남성 22명을 대상으로 정적 스트레칭 군 11명과 탄성적 스트레칭 군 11명을 스트레칭 적용 전, 적용 후 30초, 1분 후, 3분 후, 5분 후, 10분 후에 중앙주파수 및 최대 수의적 등척성 수축력의 변화를 분석하였다. 중앙주파수는 시간에 따른 변화와 군 간에서 유의한 차이를 보였다. 정적 스트레칭군과 탄성적 스트레칭군 모두에서 3분후까지 감소되었다가 증가되었다. 최대 수의적 등척성 수축력은 시간에 따른 변화와 군 간에서도 유의한 차이를 보였다. 정적 스트레칭군은 3분후까지 감소되었다가 그 이후부터 증가되었으며, 탄성적 스트레칭군은 5분후까지 감소되었다가 증가되었다. 결론적으로 스트레칭 적용 후 시간에 따라 변화를 보였으며, 정적 스트레칭보다 탄성적 스트레칭의 효과가 조금 더 길게 유지되는 것을 알 수 있었다.

• The Journal of Korean Physical Therapy
• /
• 제20권2호
• /
• pp.1-10
• /
• 2008

Purpose: This study examines the effects of elastic band of resistance exercise for balance control of the elderly. Methods: Thirty of eighty participants in experiment subjects who demonstrated balance-impairment through the use of primary screening tests including the one leg standing test (OLST), functional reach test (FRT) and timed up and go (TUG) were selected as subjects. Fifteen subjects that underwent muscle-strengthening exercise using an elastic band were selected as the exercise group and fifteen subjects were selected as a control group. Subjects undertook a home-based exercise program three times per week for 9 weeks. Muscle strength, functional assessment and a balance test were quantitatively measured before and after the exercise regimen. Results: After muscle strengthening exercises, changes in maximal voluntary isometric contraction (MVIC) showed a significant increase in all of the lower extremity muscles of the exercise group subjects. There were statistically significant differences between the exercise and control groups for changes in the OLST, FRT and TUG, which are functional assessments of balance ability, and changes of the unit path length and circumference area, measurement items of quantitative analysis. In addition, from examining correlations between MVIC, balance ability, it was found that an increase of muscle strength in the hip joint group of muscles among the lower extremity muscles had greater improvement in correlation with balance ability in this elderly population. Conclusion: Resistance exercise using elastic bands had significant effects on muscle strengthening in elderly subjects, with a resultant increase of lower extremity muscle strength with significant improvement of balance ability.

• 한국전문물리치료학회지
• /
• 제10권1호
• /
• pp.51-62
• /
• 2003

The purpose of this study was to compare the relative accuracy of a range of computer-based analysis with respect to EMG onset determined visually by an experienced examiner. Ten healthy students (6 male, 4 female) were recruited and three times randomly selected trials of isometric contraction of wrist flexion and extension were evaluated using four technique. These methods were compared which varied in terms of EMG processing, threshold value and the number of samples for which the mean must exceed the defined threshold, and beyond 7% of maximum amplitude. To identify determination of onset time, ICCs(Intraclass Correlation Coefficients) was used and inter-rater arid intra-rater reliability ranged good in visually derived onset values. The results of this study present that in wrist flexion and extension, the reliability of the inter and intra-examiner muscle contraction onset times through visual analysis showed beyond .971 with ICCs. The reliability of the muscle contraction onset time decision through visual reading, tested with computer analysis, showed a relationship of all the selected analysis methods with ICCs .859 and .871. The objective computer-based analysis comparing with visual reading at the same time is the effective and qualitative data analysis method, considering the specificity of each study method.

• 한국운동역학회지
• /
• 제17권3호
• /
• pp.61-68
• /
• 2007

When an active muscle is stretched, its steady-state isometric force following stretch is greater than that of a purely isometric contraction as the corresponding muscle length, referred to as force enhancement (FE). The purpose of this study was to investigate possible effects of muscle architecture on the FE. While subject performed maximal isometric dorsiflexion (REF) and isometric-stretch-isometric dorsiflexion (ECC) contractions, ankle joint angle and dorsiflexion torque using a dynamometer and electromyography of the tibialis anterior and the medical gastrocnemius muscles were measure. Simultaneously, real-time ultrasound images of the tibialis anterior were acquired. Regardless of the speed of stretch of the ECC contractions. the torques produced during the isometric phase following stretch ($37.3{\pm}1.5\;Nm$ ($10{\pm}3%$ FE) and $38.3{\pm}1.5$ ($12{\pm}3%$ FE) for the ECC contractions with $15^{\circ}$/s and $45^{\circ}$/s stretch speeds, respectively) were greater than those of the REF contractions ($34.5{\pm}2.5\;Nm$). Moreover, the amount of FE was found to be stretch speed dependent. Angles of pennation ($\alpha$) during the isometric phase following stretch were the same for the REF ($15{\pm}1^{\circ}$) and the ECC ($14{\pm}1^{\circ}$(LS), $15{\pm}1^{\circ}$(LF)). During the same phase, muscle thicknesses were the same ($14.9{\pm}0.6$, and $14.9{\pm}0.5\;mm$ for the REF and the ECC contractions, respectively). For a large limb muscle, the tibialis anterior muscle, a similar amount of force enhancement was observed as did for other human skeletal muscles. Architectural variables, pennation angle and thickness, were not systematically different between the REF and ECC contractions when FE occurred. Therefore, the results of this study suggest that muscle architecture may have little influence on the production of FE.