Rectus Femoris Muscle Activity Research Articles

세로발활 높이와 트레드밀 경사도 차이에 따른 하지의 근활성도 비교

본 연구는 세로발활 높이와 트레드밀 경사도 차이에 따른 하지의 근활성도를 비교하여 효율적인 보행 운동에 관련 기초자료를 제시하고자 하였다. 하지에 정형외과적 및 관절가동범위에 제한이 없는 학생 17명을 대상으로 세로발활 높이를 정상발과 편평발로 나누어 경사도 $0^{\circ}$ , 오르막 $5^{\circ}$ , $10^{\circ}$ , $15^{\circ}$ , 내리막 $5^{\circ}$ , $10^{\circ}$ , $15^{\circ}$ 에서 넙다리 곧은근, 넙다리 두갈래근, 앞정강이근, 장딴지근 가쪽과 안쪽 5개 근육의 근활성도를 측정하였다. 경사도 비교 결과 통계학적으로 유의하였고(p $0^{\circ}$ 과 내림 $15^{\circ}$ 에서 유의한 차이가 있었다(p .05). 이러한 결과로 미루어 볼 때 정상발과 편평발은 하지 근활성도에서 차이를 나타냄을 알 수 있었다. 따라서 앞으로는 본 연구의 제한점을 보완하여 좀 더 많은 연구가 이루어져야 할 것이다. 【The purpose of this study was to compare the lower extremity muscle activities according to the different longitudinal arch and treadmill inclination and to provide basic data on treadmill walking exercise. The selected 17 subjects who had not lower extremity injury and ROM limitation were recruited in this study. The longitudinal arch was divided into normal foot and flat foot. The inclinations of the treadmill were $0^{\circ}$ , up hill $5^{\circ}$ , $10^{\circ}$ , $15^{\circ}$ , down hill $5^{\circ}$ , $10^{\circ}$ and $15^{\circ}$ . The electromyography was used to analyze the muscle activity of rectus femoris, biceps femoris, tibialis anterior, gastrocnemius lateralis and medialis. There were significant differences between the inclination $0^{\circ}$ and down hill $15^{\circ}$ . There was no interactive effect of treadmill inclination on the longitudinal arch. The activity difference of lower extremity muscle was not conspicious. There existed the interactive effect between the longitudinal arch and muscle activity. The contrast test within subjects showed positively in the rectus femoris and gastrocnemius medialis, biceps femoris and gastrocnemius medialis. The different longitudinal arch did not influence on the effect(p>.05). There was significant difference between the normal foot and the flat foot. So it is necessary to carry out the long term study.】

대퇴신경 손상 환아의 보행분석 : 사례연구

The femoral nerve innervates the quadriceps muscles and its dermatome supplies anteromedial thigh and medial foot. Paralysis of the quadriceps muscles due to the injury of the femoral nerve results in disability of the knee joint extension and loss of sensory of the thigh. A child could walk independently even though he had injured his femoral nerve severely due to the penetrating wound in the medial thigh. We measured and analyzed his gait performance in order to find the mechanisms that enabled him to walk independently. The child was eleven-year-old boy and he could not extend his knee voluntarily at all during a month after the injury. His gait analysis was performed five times (GA1~GA5) for sixteen months. His temporal-spatial parameters were not significantly different after the GA2 or GA3 test, and significant asymmetry was not observed except the single support time in GA1 results. The Lower limb joint angles in affected side had large differences in GA1 compared with the normal normative patterns. There were little knee joint flexion and extension motion during the stance phase in GA1 The maximum ankle plantar/dorsi flexion angles and the maximum knee extension angles were different from the normal values in the sound side. Asymmetries of the joint angles were analyzed by using the peak values. Significant asymmetries were found in GA1with seven parameters (ankle: peak planter flexion angle in stance phase, range of motion; ROM, knee: peak flexion angles during both stance and swing phase, ROM, hip: peak extension angle, ROM) while only two parameters (maximum hip extension angle and ROM of hip joint) had significant differences in GA5. The mid-stance valleys were not observed in both right and left sides of vertical ground reaction force (GRF) in the GA1, GA2. The loading response peak was far larger than the terminal stance peak of vertical ground reaction curve in the affected side of the GA3, GA4, GA5. The measured joint moment curves of the GA1, GA2, GA3 had large deviations and all of kinetic results had differences with the normal patterns. EMG signals described an absence of the rectus femoris muscle activity in the GA1 and GA2 (affected side). The EMG signals were detected in the GA3 and GA4 but their patterns were not normal yet, then their normal patterns were detected in the GA5. Through these following gait analysis of a child who had selective injuries on the knee extensor muscles, we could verify the actual functions of the knee extensor muscles during gait, and we also could observe his recovery and asymmetry with quantitative data during his rehabilitation.

Safe and effective quadriceps femoris muscle exercise of resisted front bridge with a leg support in patients with anterior cruciate ligament insufficiency

BackgroundMuscle strengthen exercise of quadriceps femoris is important but risky to the anterior cruciate ligament (ACL) graft, because quadriceps muscle exercise near the knee extension may causes anterior tibial translation....

The change of gait parameters during walking at different percentage of preferred walking speed for healthy adults aged 20–60 years

This study aims to investigate the effects of age, gender and walking speed on the gait performance during walking at a range of percentage of preferred walking speed (PPWS). The subjects were aged from 20 to 60 years and both genders were equally represented. A nested-factorial analysis of variance was employed. The independent variables include walking speed (80%, 100%, 120%, and 140% PPWS), age (young, middle, and older groups) and gender. The response measures include lower limb joint motion, vertical ground reaction force (VGRF), muscle electromyography (EMG), heart rate, and perceived exertion of whole body and local areas. The results show that different age and gender groups had similar gait performance on most of the joint motions, HR, as well as the perceived exertions while walking at a range of PPWS. In addition, these performance generally increased with the increasing walking speed and the trend becomes more obvious when the speed was higher than 120% PWS. Age and gender differences have been found in VGRFs and muscle EMG. Females exhibited significantly higher VGRF in the heel-strike and toe-off stages, as well as higher tibialis anterior muscle activity. Older subjects had significantly higher rectus femoris muscle activity than younger adults. Besides, the interaction between gender and walking speed was significant on VGRF in the toe-off stage. Further discussions are addressed.

Age and electromyographic frequency alterations during walking in children with cerebral palsy

The use of surface electromyography (sEMG) recorded during ambulation has provided valuable insight into motor development and changes with age in the pediatric population. However, no studies have reported sEMG differences with age in the children with cerebral palsy (CP). In this study, data from 50 children were divided retrospectively into four groups, representing either an older (above the age of seven years) or younger (below the age of seven years) age group with either typical development (TD) or CP. Data were analyzed from 16 children in the younger age group with TD, and eight in the older age group with TD. Data were also available from 14 in the younger age group with CP, and 12 in the older age group with CP. SEMG signals from the rectus femoris (RF) and medial hamstring (MH) were analyzed using wavelet techniques to examine time–frequency content. RF muscle activity was statistically different between all groups ( p < 0.001), with an elevated instantaneous mean frequency (IMNF) in the older TD group than the younger TD group, an elevated IMNF in the younger CP group than the older CP group, and elevated IMNF in both CP groups compared to both TD groups. Activity for the MH muscle followed the same pattern except for the CP young and old group comparison, which indicated no difference. The results indicate that differences in neuromuscular activation exist between younger and older groups of children with both TD and CP, and may provide new insight into muscle activity pattern changes during the development of walking.

Insight into Muscle Activity during Deep Water Running

The purpose of this study was to compare muscle activity and patterns during deep water running (DWR) and treadmill running (TMR) at equivalent levels of RPE. Subjects (n = 7, 26.3 ± 4.3 yr, 158.2 ± 9.9 cm, 61.0 ± 6.6 kg) performed DWR and TMR at RPE values of 11 (fairly light), 13 (somewhat hard), and 15 (hard). Surface EMG was used to evaluate muscle activity of the rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius (GA) with average EMG calculated across a 30-s window. Five cycles of data were extracted from smoothed EMG profiles on the basis of the selection of distinct RF peaks. These cycles were reduced to create ensemble muscle activity patterns per condition. Average EMG for each muscle was analyzed using a repeated-measures ANOVA with Bonferroni's post hoc tests. TA and GA muscle activity magnitudes during DWR were significantly lower than during TMR (mean decrease of 72%-86%, P < 0.05) for any RPE level. BF and RF muscle activity magnitudes were either not different or tended to be lower during DWR than TMR for matched RPE (P = 0.051 and P = 0.121, respectively). Whereas TA and GA muscle activity magnitudes were each clearly lower during DWR than TMR regardless of RPE, higher levels of intensity (RPE 15) during DWR can be used to elicit similar muscle activity levels as lower intensity (RPE 11) TMR.

파킨슨 환자들의 방향전환 보행 향상을 위한 하지의 운동학 및 근육 활동 규명

본 연구의 목적은 파킨슨 환자들에게 일상생활 속에서 빈번히 수행되는 방향전환 동작 중에 작용하는 하지의 운동학 및 근육의 활동을 규명하는데 있다. 호엔야르 <TEX>$1.5{\sim}4$</TEX>척도의 60대 파킨슨 환자 7명이 본 실험에 참여하였다. 실험실 바닥에 직선(<TEX>$0^{\circ}$</TEX>) 및 방향전환(<TEX>$60^{\circ}$</TEX>, <TEX>$90^{\circ}$</TEX>, <TEX>$120^{\circ}$</TEX>) 보행로를 만들었다. 보행로에 5cm 넓이의 검은색 접착테이프를 붙여 놓아, 그 경로를 따라 무작위 순서로 지나가도록 하였다. 하지의 운동학적 변인을 측정하기 위해 해당부실에 21개의 마커를 부착하였으며, 근전도 변인을 측정하기 위해 우측 하지의 장내전근, 중둔근, 대둔근, 대퇴이두근, 대퇴직근, 비복근, 전경골근에 전극을 부착하였다. 방향전환 각도별(4수준: <TEX>$0^{\circ}$</TEX>, <TEX>$60^{\circ}$</TEX>, <TEX>$90^{\circ}$</TEX>, <TEX>$120^{\circ}$</TEX>)로 얻은 하지의 운동학 및 근전도 변인의 차이를 규명하기 위하여 반복이 있는 일원 변량 분석을 실시하였다. 파킨슨 환자들은 방향전환시 활보장과 보간을 감소시키는 것으로 나타났으며, 하지에 작용하는 근육활동에는 차이가 없는 것으로 나타났다. The purpose of this study was to investigate the lower extremity kinematics and muscle activities of adductor longus(AL), gluteus medius(GME), gluteus maximus(GMA), biceps femoris(BF), rectus femoris(RF), gastrocnemius(GA), and tibialis anterior(TA) using three dimensional and Noraxon 8 channels EMG system during turn 0, 60, 90 and 120 degrees in patients with Parkinson's disease. Seven parkinson's patients and five healthy subjects were participated in the study. Participants with Parkinson's disease demonstrated significant differences in reduction of stride length and stride width. Also, they showed ill difference in muscle activities. The strength and balance of the lower extremity muscles may help to improve cutting movement and to prevent falling in parkinson's patients.

Effects of educational intervention on joint angles of the trunk and lower extremity and on muscle activities during patient-handling tasks

The objective of this study was to examine the effects of educational intervention on joint angles of the trunk and lower extremity and on muscle activities during patient-handling task. Thirty-two subjects (17 males and 15 females) volunteered for the study. They were classified into three groups: intervention group 1, comprised of first grade physical therapist students; control group, which included first grade occupational therapist students; intervention group 2, which comprised third grade physical therapist students. The educational intervention during the experimental period consisted of: (1) 12 regular classes and short-term clinical practice for the students of intervention group 1; (2) long-term clinical practice, relating to patient-handling task, for the students of intervention group 2. The following experiments were repeated before and after the educational intervention. Each subject was asked to transfer a male (55 kg) from one chair to a second chair (left to right) and then back again to the original chair (right to left). The flexion angles of the trunk, hip and knee joints were quantified by means of the dynamic three-dimensional biomechanical analysis. Muscle activities (% maximum voluntary contraction, %MVC) of biceps brachii, trapezius, rectus femoris and erector spinae muscles were measured using surface electromyography (EMG). The effects of group, gender, measurement time and side on joint angles of trunk and lower extremity, %MVC of four muscle activities and transfer time were assessed. Although the EMG analysis could not clearly demonstrate any reduction of physical load to the low back, the flexion angles of the hip and knee joints of student subjects during the patient-handling task became larger and that of the trunk became smaller in the group given the educational intervention. The finding of this study suggests that the posture of the study subjects changed to the squat lifting method, which is preferable for reducing the physical load to the lower back, as a result of the educational intervention.

An Electromyographic Analysis of the Ab-Slide Exercise, Abdominal Crunch, Supine Double Leg Thrust, and Side Bridge in Healthy Young Adults: Implications for Rehabilitation Professionals

The purpose of this study was to examine the effectiveness of a commercial abdominal machine (Ab-Slide) and three common abdominal strengthening exercises (abdominal crunch, supine double leg thrust, and side bridge) on activating abdominal and minimizing extraneous (nonabdominal) musculature-namely, the rectus femoris muscle. We recruited 10 males and 12 females whose mean (+/- SD) percent body fat was 10.7 +/- 4 and 20.7% +/- 3.2%, respectively. Electromyographic (EMG) data were recorded using surface electrodes for the rectus abdominis, external oblique, internal oblique, and rectus femoris. We recorded peak EMG activity for each muscle during each of the four exercises and normalized the EMG values by maximum muscle contractions (% MVIC). A two-factor repeated-measures analysis of variance assessed differences in normalized EMG activity among the different exercise variations (p < 0.05). Post hoc analyses were performed using the Bonferroni-adjusted alpha to assess between-exercise pair comparisons (p < 0.002). Gender did not affect performance; hence, data were collapsed across gender. We found a muscle x exercise interaction (F9,189 = 5.2, p < 0.001). Post hoc analyses revealed six pairwise differences. The Ab-Slide elicited the greatest EMG activity for the abdominal muscles and the least for the rectus femoris. The supine double leg thrust could be a problem for patients with low-back pathology due to high rectus femoris muscle activity.

Quadriceps and hamstrings muscle control in athletic males and females

The aim of this study was to investigate whether athletic males and females have differences in their quadriceps and hamstrings muscle control strategies. Twenty-four people (12 males, 12 females) active in level I activities volunteered to participate. The subjects' muscle control strategies were studied using electromyography and a target matching protocol that assesses one's ability to produce force with control. The degree of control exhibited in the subjects' quadriceps and hamstrings muscle activation strategies was evaluated by calculating specificity indices for each muscle using circular statistics. Females displayed significantly lower specificity than males in their vastus medialis (p < 0.001), rectus femoris (p = 0.044), and lateral hamstrings (p = 0.001) muscle activity patterns, but similar specificity in their vastus lateralis and medial hamstrings activity patterns. Females also used a significantly higher magnitude of vastus lateralis (p < 0.001) and vastus medialis (p < 0.001) muscle activity than males to achieve the same relative force level. These findings indicate athletic males and females have differences in their knee muscle control strategies.

Age-Related Differences in Tai Chi Gait Kinematics and Leg Muscle Electromyography: A Pilot Study

Wu G. Age-related differences in Tai Chi gait kinematics and leg muscle electromyography: a pilot study. Objective To compare the biomechanic features of Tai Chi gait by elders with those by young adults, and with those of normative gait. Design Cross-sectional study. Setting Laboratory-based testing. Participants Young (n=6; 3 women) and old (n=6; 5 women) Tai Chi practitioners. Intervention All subjects had practiced Tai Chi for at least 4 months. Main Outcome Measures Spatial, temporal, and leg muscle electromyography during Tai Chi gait and normative gait. Results The primary age-related differences in Tai Chi gait were during single stance, with elders having significantly shorter single-stance time (−50%), less lateral displacement (–30%), knee flexion (–42%), hip flexion (–39%), activation time in the tibialis anterior (–13%), soleus (–39%), and tensor fascia lata (TFL) (–21%), activation magnitude in the tibialis anterior (–39%), and coactivation time of the tibialis anterior and soleus (–47%). Compared with normative gait, elders during Tai Chi gait had significantly larger knee (139%) and hip (66%) flexions, longer duration (90%–170%) and higher magnitude (200%–400%) of the tibialis anterior, rectus femoris, and TFL muscle activities, and longer duration of coactivation of most leg muscle pairs (130%–380%). Conclusions The elders practice Tai Chi gait in higher posture than younger subjects. The Tai Chi gait poses significantly higher challenges to elder’s balance and muscular system than does their normative gait.

Neuromuscular and Lower Limb Biomechanical Differences Exist between Male and Female Elite Adolescent Soccer Players during an Unanticipated Side-cut Maneuver

Background Female athletes are 2 to 8 times more likely than male athletes to injure the anterior cruciate ligament during a noncontact athletic maneuver. Identifying anterior cruciate ligament injury risk factors in female athletes may help with the development of preventive training programs aimed at reducing injury rates. Hypothesis Differences between genders in lower limb kinematics, kinetics, and neuromuscular patterns will be identified in an adolescent soccer population during an unanticipated side-cut maneuver. Study Design Controlled laboratory study. Methods Forty-two elite adolescent soccer players (21 male and 21 female) performed an unanticipated side-cut maneuver, with the 3-dimensional kinematic, kinetic, and electromyographic lower limb data being analyzed using principal component analysis. Results The female athletes had higher gastrocnemius activity, normalized to maximal voluntary isometric contractions, and a mediolateral gastrocnemius activation imbalance that was not present in the male athletes during early stance to midstance of the side-cut. Female athletes demonstrated greater rectus femoris muscle activity throughout stance, and the only hamstring difference identified was a mediolateral activation imbalance in male athletes only. Female athletes performed the side-cut with less hip flexion and more hip external rotation and also generated a smaller hip flexion moment compared with the male athletes. Conclusion This is the first study to identify gender-related differences in gastrocnemius muscle activity during an unanticipated cutting maneuver. Clinical Relevance The increased and imbalanced gastrocnemius muscle activity, combined with increased rectus femoris muscle activity and reduced hip flexion angles and moments in female subjects, may all have important contributing roles in the higher noncontact ACL injury rates observed in female athletes.

신발 아웃솔의 굴곡 형태에 따른 하지근육활동의 특성과 보행 패턴의 비교연구

The purpose of this study was to investigate muscle activity and gait pattern in lower limb depending on the outsole of heel rockers. Fifteen healthy men volunteered for this experiment. Each subject performed totally three trails with two pairs of different heel rocker shoes and a pair of normal running shoes at speed of 1.33m/s for 1 minute during walking on a treadmill. Kinematic data gathered in 100Hz was recorded and analyzed by using the 3D motion capture system to measure the trunk tilt and joint angle of the right lower limb. And the lower extremity muscle activities were simultaneously recorded in 1000Hz and assessed by using EMG. The statistical analysis was the one-way ANOVA with the repeated measures to compare among the three kinds of shoes. The level of statistical significance for all tests was 0.05. Joint angle of lower limb was showed statistically significant different in MST(hip joint), LHS(ankle joint), and RTO(knee and ankle joint). Muscle activity of rectus femoris and biceps femoris was statistically increased in both heel rocker shoes during gait cycle on treadmill. The maximum peak time of tibialis anterior in the negative heel rocker showed the delay of approximately 23.8%time than normal shoes. Gait pattern variability of the negative heel rocker was increased in the first half of the stance phase and the variability of the positive heel rocker was increased in the terminal stance phase. In Conclusion, stability was decreased in between joints of lower limb on positive heel rocker than negative heel rocker. This study found that there were different joint angle, muscle activity, gait pattern and coordinate system of the lower limb in each kind of shoes. These unstability affected the lower extremity and the whole body. A further study has to be continued with study of rehabilitation and exercise for a long-term.

Electromyographic analysis of traditional and nontraditional abdominal exercises: implications for rehabilitation and training

BACKGROUND AND PURPOSE: Performing nontraditional abdominal exercises with devices such as abdominal straps, the Power Wheel, and the Ab Revolutionizer has been suggested as a way to activate abdominal and extraneous (nonabdominal) musculature as effectively as more traditional abdominal exercises, such as the crunch and bent‐knee sit‐up. The purpose of this study was to test the effectiveness of traditional and nontraditional abdominal exercises in activating abdominal and extraneous musculature.SUBJECTS: Twenty‐one men and women who were healthy and between 23 and 43 years of age were recruited for this study.METHODS: Surface electromyography (EMG) was used to assess muscle activity from the upper and lower rectus abdominis, external and internal oblique, rectus femoris, latissimus dorsi, and lumbar paraspinal muscles while each exercise was performed. The EMG data were normalized to maximum voluntary muscle contractions. Differences in muscle activity were assessed by one‐way, repeated‐measures analysis of variance.RESULTS: Upper and lower rectus abdominis, internal oblique, and latissimus dorsi muscle EMG activity were highest for the Power Wheel (pike, knee‐up, and roll‐out), hanging knee‐up with straps, and reverse crunch inclined 30°. External oblique muscle EMG activity was highest for the Power Wheel (pike, knee‐up, and roll‐out) and hanging knee‐up with straps. Rectus femoris muscle EMG activity was highest for the Power Wheel (pike and knee‐up), reverse crunch inclined 30°, and bent‐knee sit‐up. Lumbar paraspinal muscle EMG activity was low and similar among exercises.DISCUSSION AND CONCLUSION: The Power Wheel (pike, knee‐up, and roll‐out), hanging knee‐up with straps, and reverse crunch inclined 30° not only were the most effective exercises in activating abdominal musculature but also were the most effective in activating extraneous musculature. The relatively high rectus femoris muscle activity obtained with the Power Wheel (pike and knee‐up), reverse crunch inclined 30°, and bent‐knee sit‐up may be problematic for some people with low back problems.

Electromyographic Analysis of Traditional and Nontraditional Abdominal Exercises: Implications for Rehabilitation and Training

Performing nontraditional abdominal exercises with devices such as abdominal straps, the Power Wheel, and the Ab Revolutionizer has been suggested as a way to activate abdominal and extraneous (nonabdominal) musculature as effectively as more traditional abdominal exercises, such as the crunch and bent-knee sit-up. The purpose of this study was to test the effectiveness of traditional and nontraditional abdominal exercises in activating abdominal and extraneous musculature. Twenty-one men and women who were healthy and between 23 and 43 years of age were recruited for this study. Surface electromyography (EMG) was used to assess muscle activity from the upper and lower rectus abdominis, external and internal oblique, rectus femoris, latissimus dorsi, and lumbar paraspinal muscles while each exercise was performed. The EMG data were normalized to maximum voluntary muscle contractions. Differences in muscle activity were assessed by a 1-way, repeated-measures analysis of variance. Upper and lower rectus abdominis, internal oblique, and latissimus dorsi muscle EMG activity were highest for the Power Wheel (pike, knee-up, and roll-out), hanging knee-up with straps, and reverse crunch inclined 30 degrees. External oblique muscle EMG activity was highest for the Power Wheel (pike, knee-up, and roll-out) and hanging knee-up with straps. Rectus femoris muscle EMG activity was highest for the Power Wheel (pike and knee-up), reverse crunch inclined 30 degrees, and bent-knee sit-up. Lumbar paraspinal muscle EMG activity was low and similar among exercises. The Power Wheel (pike, knee-up, and roll-out), hanging knee-up with straps, and reverse crunch inclined 30 degrees not only were the most effective exercises in activating abdominal musculature but also were the most effective in activating extraneous musculature. The relatively high rectus femoris muscle activity obtained with the Power Wheel (pike and knee-up), reverse crunch inclined 30 degrees, and bent-knee sit-up may be problematic for some people with low back problems.

Gender Comparison of Hip Muscle Activity During Single-Leg Landing

Controlled laboratory study. To determine whether gender differences in electromyographic (EMG) activity of hip-stabilizing muscles are present during single-leg landing. Numerous factors may explain the greater rate of anterior cruciate ligament (ACL) injuries in female athletes. However, gender differences in hip muscle activity during dynamic events have not been well characterized. Twenty-two Division I collegiate athletes (13 female, 9 male) performed drop landings from 30.5- and 45.8-cm heights. Surface EMG was used to examine relative muscle activity from 200 milliseconds prior to initial contact to 250 milliseconds postcontact. Peak and mean values for each muscle (gluteus maximus, gluteus medius, rectus femoris) in each time epoch were analyzed using 2 x 2 (group by height) analyses of variance (ANOVAs) to determine significance. Females demonstrated lower gluteus maximus peak (mean +/- SD, 69.5 +/- 30.2 versus 98.0 +/- 33.4 percent maximum voluntary contraction [%MVIC]; P= .019) and mean (mean +/- SD, 37.5 +/- 15.6 versus 53.9 +/- 18.0 %MVIC; P = .018) muscle activation during the postcontact phase of landing than males. Furthermore, females demonstrated greater peak rectus femoris activity during the precontact phase (mean +/- SD, 33.6 +/- 18.5 versus 18.7 +/- 8.2 %MVIC; P = .029). A positive effect of drop height on relative activity of all muscles was observed during both phases (P<.05). Females utilize different muscular activation patterns compared to males (ie, decreased gluteus maximus and increased rectus femoris muscle activity) during landing maneuvers. Decreased hip muscle activity and increased quadriceps activity may be important contributors to the increased susceptibility of female athletes to noncontact ACL injuries.

사이클 운동시 페달 샤프트 너비에 따른 근육 활동 비교

본 연구의 목적은 사이클 운동 시, 3가지 다른 길이의 페달 샤프트 (표준형, 5.08 cm, 10.16 cm)가 근육활동에 미치는 영향을 근전도 측정을 통해 비교 분석하는데 있다. 사이클링을 활동적으로 하는 여학생 5명을 피험자로 선택하여 대퇴지근(RF), 외측광근(VL), 내측광근(VM) 대퇴이두근(BF)을 표면전극을 사용하여 관찰하였다. 자료 분석을 위해 두 대의 S-VHS 카메라 (Panasonic Digital 5000)를 사용하여 사이클링 동작을 촬영하였다. 연구의 목적을 위해 각 조건에 대한 표준화된 평균 및 최대 근전도치가 계산되어졌다. 각각의 변인에 대해 페달 샤프트의 길이에 따른 근전도치의 차이점을 분석하기 위해 반복측정에 의한 일원변량분석을 사용하였으며, 통계적 유의성이 있을 경우 Newman-Keuls 사후검증을 실시하였다. 일반적으로 5.08 cm 길이의 페달 샤프트를 사용했을 경우 표준형의 페달 샤프트와는 다르게 모든 하지근의 적분 근전도치가 줄어드는 것으로 나타났다. 페달 샤프트의 길이가 길어짐에 따라 외측광근의 적분 근전도치가 통계적으로 유의하게 낮게 나타났고, 5.08 cm 길이에서 대퇴이두근의 적분 근전도치가 통계적으로 유의하게 낮게 나타났다. 페달 샤프트 길이에 따른 최대 근전도치의 통계적 유의성을 찾을 수 없었지만, 일반적으로 5.08 cm 길이의 페달 샤프트를 사용할 때 최대 근전도치가 가장 낮게 나타났다. 본 연구의 결과, 페달 샤프트의 길이가 하지근의 활동정도와 형태를 변화시킨다는 것을 알 수 있었으며, 하지관절의 부하에 영향을 미치는 것으로 사료되어진다. 이에 따라, 개인의 해부 구조학적인 면을 고려한 페달 샤프트의 길이 조절은 효율적이며 안정적인 사이클링 동작을 수행하는데 많은 도움이 될 수 있을 것이다.

Keep on your toes: gait initiation from toe-standing

Gait initiation from toe-standing is common in patients with upper motor neurone (UMN) pathology as well as in able-bodied subjects during certain dance and athletic situations. It is unclear whether balance problems in patients who toe-walk are due to the underlying pathology, or due to initiating gait from toe-standing. The aim of this study was to compare the biomechanics of gait initiation from toe-standing to that from heel–toe standing in healthy able-bodied subjects. Data were collected for three seconds prior to, and three seconds after, a visual signal to initiate gait. Ground reaction force and centre of pressure (COP) data were collected with an AMTI force platform, and electromyographic and kinematic data were collected from each limb with a Vicon motion analysis system. When initiating gait from toe-standing, there was a smaller backward displacement of the COP compared to heel–toe standing. In addition, greater forward momentum was generated, and there was an increase in gastrocnemius, rectus femoris and biceps femoris muscle activity. There were no differences in COP displacement or momentum generated in the mediolateral direction for the two conditions. Thus, initiating gait from toe-standing allows one to generate greater amounts of forward momentum but not at the expense of generating excessive stance-side momentum. This may be an advantageous method of initiating movement for dancers and athletes in certain situations. This work also suggests that balance problems in patients with UMN pathology are likely due to the underlying pathology and are not due to initiating gait from toe-standing.

Reproducibility of kinetics of electromyogram spectrum parameters during dynamic exercise.

During incremental exercise on a cycle ergometer a study was made of the reproducibility of changes in electromyographic activity (EMG) of human quadriceps muscles. Seven subjects performed three periods of incremental exercise either every 2 weeks (G1: four subjects) or 6 weeks (G2: three subjects). Each test was normalized with respect to the maximal aerobic power (MAP) of the subject. It consisted of a quasilinear increase in mechanical power (from 20% to 100% MAP) during 8 min. For rectus femoris muscle activity, changes in total power spectrum (PEMG) and in mean power frequency (MPF) were fitted by a 3rd order polynomial function (named profile) and normalized with respect to the maximal value for PEMG and to the mean value for MPF. A curvilinear increase was found for PEMG. The MPF kinetics varied from one subject to another. These changes were either a continuous increase, or a continuous decrease, or an increase followed by a decrease. Only for G2, was MAP determined before each test in order to update the limits of the test. A good reproducibility of PEMG was shown by its mean magnitude [95.88%, (SD 3.92)] and by computing a mean correlation coefficient between profiles two by two [r2 = 0.948 (SD 0.028) n = 21]. Intraclass coefficient correlation (ICC) calculated for each subject indicated a high level of reproducibility for five of the seven subjects (ICC > 0.80). No clear effect of MAP updating on PEMG and MPF profile reproducibility was observed. Thus it is suggested that MPF kinetics may characterize a subject at a given moment while PEMG kinetics may illustrate a normal profile, and they may both characterize EMG changes for a population during incremental exercise.

Evaluation of Impact on Human Body at Heel Contact.

Impact created by the heel striking the floor leads to problems among athletes or patients having artificial joints. The impact force was evaluated using the ellipsoid of impact force and simple models. As the ellipsoid of impact force is derived from a kinematic relation between momentum immediately before and after striking the floor, it is easily applicable to other types of walking such as on steps or slope. The concept of equivalent mass and the center of impact force was also introduced. The mass is determined by the configuration of the leg at heel contact or the heel landing style of a runner. The center of impact force depends on the acting point of the force on the foot and reduces the effect of impact force on the ankle joint. The ellipsoid of impact force suggested the following : the impact force on the distal point of the shank in footless model was remarkably reduced by the assumption of foot ; and some degree of flexion of the knee reduced the impact force and took a minimum value. Experimental results of walking on the floor showed that the transfer of acceleration of impact force to upper elements was greatly attenuated at ankle and knee joints corresponding to normal and fixed ankle walking, respectively. In a running test using shoes with a cushioning material at the heel, the muscle activity of rectus femoris increased as the material hardness increased.