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1.
ABSTRACT

This study aimed to examine the characteristics of electromyography (EMG) and kinematics of the supporting leg affecting energy cost while running at incline, level, and decline slopes. Twelve male Japanese middle- and long-distance runners volunteered for this study. The subjects were asked to run at 13.5 km·h?1 on a treadmill under three slope conditions. Sagittal plane kinematics and the EMG of the lower limb muscles, respiratory gases were recorded. Energy cost differed significantly between slopes, being the lowest in decline slope and the greatest in incline slope. Integrated EMG (iEMG) of leg extensor muscles was greater in the incline slope than in the decline slope, and iEMG of the gastrocnemius and soleus muscles correlated positively with energy cost. The knee and ankle joint kinematics were associated with energy cost during running. In incline slope, the knee and ankle joints were more extended (plantarflexed) to lift the body. These movements may disturb the coordination between the ankle and knee joints. The gastrocnemius muscle would do greater mechanical work to plantarflex the ankle joint rather than transfer mechanical energy as well as greater mechanical work of mono-articular muscles. These muscular activities would increase energy cost.  相似文献   

2.
运用IsoMed2000型肌力测试系统，选择60°/s和240°/s，对23名优秀男子散打运动员（健将级9名为A组，国家一级14名为B组）支撑腿和进攻腿髋、膝、踝屈伸肌群各项等速肌力指标进行测量。探讨优秀散打运动员支撑腿和进攻腿髋、膝、踝关节等速肌力特征，分析两腿的肌力差异，判断肌力平衡、关节稳定，运动员等级水平对肌力的影响。结果：国家健将级散打运动员双侧下肢髋、膝、踝关节等速肌力及稳定性显著优于国家一级运动员，支撑腿主要体现力的有效传递及稳定性，进攻腿主要体现屈伸肌力大小。  相似文献   

3.
Abstract

Exponential fatigue curves for dynamic work of the forearm muscles were obtained from 200 boys arid girls ranging from 8 through 17 years of age. The fatigue parameters analyzed in relation to initial strength were fatigable strength, steady-state equilibrium strength, and relative rate of strength loss per contraction. Older children were stronger and exhibited greater fatigue. When their strength loss and steady-state levels were considered in relation to their initial strength-capacity, there were no age differences in fatigability, and sex differences were either absent or very small. At age eight, boys and girls had equal rates of strength loss per muscle contraction. Older boys, since they exerted more strength initially, tended to reach the fatigue level more rapidly than younger children. Older girls reached their fatigue level more slowly.  相似文献   

4.
Abstract

The purposes of this study were (a) to determine whether or not selected measures of kinesthesis, involving arm positioning, were related to measures of accuracy in ball rolling, and (b) to discover whether or not there were any differences between elementary school boys and girls in kinesthetic measures and in ball rolling ability measures. Forty-seven first and second grade boys and girls were tested on four arm positioning measures and two ball rolling measures. The results of the study indicated that: (a) there is no significant relationship between ball rolling and positional measures of kinesthesis; (b) there are no real differences between boys and girls in their ability to accurately repeat positional measures of kinesthesis; and (c) boys are significantly superior to girls in their ability to manipulate accurately large and small balls, as measured by the tests used in this study.  相似文献   

5.
Abstract

The purpose of this study was to determine if angular displacement between the calcaneus and the midline of the lower leg while running is related to shin splints. A secondary purpose was to compare the strength and flexibility of ankle-joint plantar flexion, dorsal flexion, inversion, and eversion of shin-splint-injured and non-shin-splint-injured subjects. Two groups of conditioned female athletes were randomly selected to participate in this study. One group had a previous history of chronic shin splints, and the other group had no history of shin-splint injury. Angular displacement between the calcaneus and the midline of the lower leg was measured from motion picture film (100 frames/second) taken while the subjects were running at two speeds, 3m/second and 5m/second. A cable tensiometer was used to measure plantar flexion, dorsal flexion, and inversion and eversion strength at the ankle joint; and a goniometer was used to measure the flexibility of the plantar flexors, dorsiflexors, invertors, and evertors at the ankle joint. The results indicated that a shin-splint-injured leg had greater angular displacement between the calcaneus and the midline of the lower leg than a healthy leg, and that shoes and speed of running had an influence upon the amount of angular displacement. In addition, the muscular strength of the plantar flexor muscle was greater in the shin-splint subjects than in the non-shin-splint subjects.  相似文献   

6.
Muscle utilisation in squat exercise depends on technique. The purpose of this study was to compare net joint moments (NJMs) and muscle activation during squats without and with restricted leg dorsiflexion. Experienced men (n = 5) and women (n = 4) performed full squats at 80% one repetition maximum. 3D motion analysis, force platform and (EMG) data were collected. Restricting anterior leg rotation reduced anterior leg (P = 0.001) and posterior thigh (P < 0.001) rotations, resulting in a smaller knee flexion range of motion (P < 0.001). At maximum squat depth, ankle plantar flexor (P < 0.001) and knee extensor (P < 0.001) NJM were higher in unrestricted squats. Hip extensor NJM (P = 0.14) was not different between squat types at maximum squat depth. Vastus lateralis (P > 0.05), vastus medialis (P > 0.05) and rectus femoris (P > 0.05) EMG were not different between squat types. Unrestricted squats have higher ankle plantar flexor and knee extensor NJM than previously reported from jumping and landing. However, ankle plantar flexor and knee extensor NJM are lower in restricted squats than previous studies of jumping and landing. The high NJM in unrestricted squat exercise performed through a full range of motion suggests this squat type would be more effective to stimulate adaptations in the lower extremity musculature than restricted squats.  相似文献   

7.
Abstract

The present study examined the relative importance of body size and composition as determinants of individual differences in isokinetic leg extensor strength in young adult males performing at slow, moderate, and fast speeds. The subjects were 31 males between the ages of 19 and 29 years, who were not participating in weight training programs. Low to moderate correlations were found between isokinetic strength and body size or body composition measurements. At each speed, similar proportions of the variance in peak torque values were accounted for by lean body weight (23-30%) and thigh volume (20-37%). However, body weight, often suggested as the best reference standard for equalizing strength scores, also accounted for only 13-24% of the variance in peak torque values at each of the speeds tested. The moderate correlations reported in this study do not support the use of body size and composition measurements as a means of adjusting strength values.  相似文献   

8.
Background:One-legged pedaling is of interest to elite cyclists and clinicians.However,muscular usage in 1-legged vs.2-legged pedaling is not fully understood.Thus,the study was aimed to examine changes in leg muscle activation patterns between 2-legged and 1-legged pedaling.Methods:Fifteen healthy young recreational cyclists performed both 1-legged and 2-legged pedaling trials at about 30 Watt per leg.Surface electromyography electrodes were placed on 10 major muscles of the left leg.Linear envelope electromyography data were integrated to quantify muscle activities for each crank cycle quadrant to evaluate muscle activation changes.Results:Overall,the prescribed constant power requirements led to reduced downstroke crank torque and extension-related muscle activities(vastus lateralis,vastus medialis,and soleus)in 1-legged pedaling.Flexion-related muscle activities(biceps femoris long head,semitendinosus,lateral gastrocnemius,medial gastrocnemius,tensor fasciae latae,and tibialis anterior)in the upstroke phase increased to compensate for the absence of contralateral leg crank torque.During the upstroke,simultaneous increases were seen in the hamstrings and uni-articular knee extensors,and in the ankle plantarflexors and dorsiflexors.At the top of the crank cycle,greater hip flexor activity stabilized the pelvis.Conclusion:The observed changes in muscle activities are due to a variety of changes in mechanical aspects of the pedaling motion when pedaling with only 1 leg,including altered crank torque patterns without the contralateral leg,reduced pelvis stability,and increased knee and ankle stiffness during the upstroke.  相似文献   

9.
ABSTRACT

Childhood physical fitness relative to adult health outcomes coupled with scant longitudinal research indicates that tracking of fitness components throughout childhood/adolescence is imperative. The study examined the stability/tracking of 9 measures of fitness for boys and girls at 5 points throughout childhood/adolescence. Tracking coefficients between individual fitness measures at various age comparisons were calculated. Using a sample with recorded data at 4 time-points, tertiles (high, moderate, low) were calculated for each fitness measure for boys and girls. Stability of fitness measures was calculated. Boys outperformed girls on fitness measures at most time points. Significantly low to moderately high tracking coefficients for each fitness measure at all time points for boys (r = .21-.79) and girls (r = .23-.89) were found. Tertile ratings remained stable across the 4 time-points. Findings highlight the importance of developing healthy fitness behaviors early in life and the significance of intervention during adolescence in low-fit youth.  相似文献   

10.
Abstract

The following measures were recorded for third- and sixth-grade children: height; weight; grip strength of the dominant and nondominant hands; elbow flexion and elbow extension strength; hip flexion and hip extension strength; dynamic balance; ball-throwing accuracy; speed of hand-arm movement; eye-hand coordination; stimulus discrimination and hand speed; perceptual ability; academic achievement; and intelligence. It was concluded that sixth-grade boys had, in general, the most favorable recorded measures, followed by sixth-grade girls, third-grade boys, and third-grade girls, these differences usually being significant.  相似文献   

11.
The purpose of this study was to investigate torque differences between 28 boys and 28 girls, ages 7 to 13 years, for the knee and elbow flexor and extensors at 30°/second and 120°/second using an isokinetic procedure (Cybex II). In addition, the relationships of these torque levels to size and age were determined. The results revealed significant (p < .05) sex differences for the knee flexor and extensor torque values at 120°/second independent of body weight. That is, the boys generated 29.2 and 39.5 foot pounds vs. the girl's 26.2 and 35.4 foot pounds for knee flexion and extension, respectively. Similarly, torque differences (p < .05) between boys and girls were present for elbow extension at 120°/second when adjusting for differences in height. When examining the flexion/extension ratios, it is apparent that increases in body size (height, weight) and age had a significant effect on the ratio at 120°/second but not at 30°/second.  相似文献   

12.
BackgroundPuberty is a critical time in the development of overweight and obesity. The aim of this study was to examine relationships between measures of adiposity, cardiovascular fitness, and biomarkers of cardiovascular disease risk in adolescents.MethodsIn a cross-sectional study design, 129 girls and 95 boys aged 12.9–14.4 years at various stages of puberty were included, along with their mothers (n = 217) and fathers (n = 207). Anthropometric assessments of adiposity were made, along with cardiovascular physical fitness, using the 20-m shuttle run test, and biomarkers associated with cardiovascular risk, including glucose, insulin, triglyceride, fibrinogen, and C-reactive protein (CRP) concentrations.ResultsWaist-to-height ratio values were similar in boys and girls and correlated positively with diastolic blood pressure, insulin, triglyceride, fibrinogen, and CRP concentrations, and inversely with cardiovascular fitness scores. Skinfold thickness measurements were higher in girls. High-molecular-weight adiponectin concentrations were lower in boys than girls, particularly in late puberty, and CRP levels were higher. Cardiovascular fitness, maternal body mass index (BMI), and paternal BMI contributed independently to the variance in waist measurements in girls and boys. Gender, triceps skinfold thickness, and weight-to-height ratio, but not parental BMI, contributed independently to the variance in cardiovascular fitness.ConclusionThere is a relationship between measures of adolescent adiposity and parental weight that involves factors other than cardiovascular fitness. Adolescent boys have relatively more abdominal fat than girls and a tendency to have a proinflammatory profile of biomarkers. These observations suggest that family and social environmental interventions are best undertaken earlier in childhood, particularly among boys.  相似文献   

13.
Abstract

This study evaluated the influence of biological and environmental variables on the differences between the throwing performance of 5-year-old girls and boys. A total of 100 children (48 girls, 52 boys) were tested on throwing for distance and rated on two components of throwing form—trunk rotation, and foot action. Children were evaluated on eight biological characteristics—height, weight, body mass index, ponderal index, sum of four skinfolds, body diameters, arm and leg girths, and somatotypes—and four environmental characteristics—older brother, older sister, presence of adult male, and playing with older children. Results indicated that boys threw farther than girls and exhibited more mature form. Boys had greater joint diameters than girls, a smaller sum of four skinfolds, and more estimated arm muscle. Boys were more likely to play regularly with older children. Girls' throwing performance was only 57% that of boys, but when throwing was adjusted for a linear composite of biological variables, girls' throwing performance increased to 69% of boys'. Thus, while the differences in most motor performance tasks between boys and girls prior to puberty have been attributed to environmental factors, some of the differences in throwing performance appears to reflect biological characteristics, even as early as 5 years of age.  相似文献   

14.
Abstract

Activity patterns of four major muscles were studied in the support leg during a standard one foot balance test. Electromyographic (EMG) activity of the tibialis anterior (TA), peroneus longus (PL), gluteus medius (GM), and adductor magnus (AM) was recorded from 10 boys (aged 7-9 yr) during 30 s balance trials. Rectified, low-pass filtered EMG data, converted to percentages of maximum contractions, were used to establish muscle activation patterns. The results showed that lateral shifts in balance were primarily mediated by the ankle musculature, while the hip muscles appeared to stabilize the pelvis. Immediately prior to lateral shifts of the center of pressure (COP), the activity of each ankle muscle was similar to the activity of the following pose. The hip muscles, however, were not consistently linked to ankle activity. Thus, the control of one-legged lateral balance does not rely on fixed hip-ankle synergies.  相似文献   

15.
Abstract

The aim of this study was to test the correlation between knee-to-hip flexion ratio during a single leg landing task and hip and knee strength, and ankle range of motion. Twenty-four male participants from a professional soccer team performed a continuous single leg jump-landing test during 10s, while lower limb kinematics data were collected using a motion analysis system. After biomechanical testing, maximal isometric hip (abduction, extension, external rotation), knee extension and flexion strength were measured. Maximum ankle dorsiflexion range of motion was assessed statically using the weight bearing lunge test. Pearson correlation coefficients were calculated to determine the associations between the predictor variables (knee and hip strength, and ankle ROM) and the main outcome measure (knee-to-hip flexion ratio). Correlation between knee-to-hip flexion ratio and hip abductors strength was significant (r = ?0.47; p = 0.019). No other significant correlations were observed among the variables (p > 0.05). These results demonstrated that a lower hip abductors strength in male soccer players was correlated with a high knee-to-hip flexion ratio during landing from a single leg jump, potentially increasing knee overload by decreasing energy absorption at the hip. The results provide a novel proposal for the functioning of hip muscles to control knee overload.  相似文献   

16.
Abstract

Fifteen highly skilled sprinters were filmed while running at maximum velocity. The results were digitized and computer processed with interest focused on the muscle moments generated about the hip, knee, and ankle of the ground leg. Muscle activity about the hip consisted of extensor (concentric) dominance from foot descent, through foot strike, and into mid-support. Muscle dominance shifted to the hip flexors (eccentric) during mid-support and continued through takeoff. Muscle dominance at the knee demonstrated a pattern of flexor (eccentric, then concentric) dominance from foot descent through foot strike and into mid-support. Knee extensors (eccentric, then concentric) then achieved dominance through takeoff. During the later stages of takeoff, the dominance decreased or reversed briefly to flexor (eccentric) activity prior to a period of minimal activity following the toe-off position. From a period of minimal activity prior and subsequent to ground contact, the plantar flexors (eccentric, then concentric) of the foot were dominant throughout the ground phase. Qualitatively, the unexpected knee flexor dominance during foot strike was generated to limit the braking action created during this portion of ground contact. The unanticipated hip flexor dominance during takeoff served to rotate the upper body forward and into the approaching air phase. In addition, both of these actions allowed efficient use of the two-joint muscles of the leg during the critical phases of ground contact. Finally, the minimizing or reversing of the knee extensor dominance during the later stages of takeoff served to protect the joint from injury. Quantitatively, the magnitude of hip extensor/knee flexor activity during foot strike was significantly related (r = .70, p = .01) to the prior occurrences of related leg injury in the subjects.  相似文献   

17.
Abstract

Congestive heart failure (CHF) patients experience reduced muscle fatigue resistance and exercise capacity. The aim of this study was to assess whether skeletal muscle in CHF patients has a normal training response compared to healthy subjects. We compared the effect of one-legged knee extensor (1-KE) endurance training in CHF patients (n=10), patients with coronary artery disease (CAD, n=9) and healthy subjects (n=13). The training response was evaluated by comparing trained leg and control leg after the training period. The fall in peak torque during 75 maximal 1-KE isokinetic contractions revealed that CHF patients were less fatigue resistant than healthy subjects in the control leg, but not in the trained leg. Peak power and peak oxygen uptake during dynamic 1-KE exercise was ~10–16% higher in trained leg than control leg. This training response was not significant different between groups. Muscle biopsies of vastus lateralis showed that fibre type composition was not different between trained leg and control leg. Capillary density was 6.5% higher in trained leg than control leg when all groups were pooled. In conclusion, the more fatigable skeletal muscle of CHF patients responds equally to endurance training compared to skeletal muscle of CAD patients and healthy subjects.  相似文献   

18.
Abstract

The main aim of this study was to determine the test–retest reliability of existing tests of health-related fitness. Participants (mean age 14.8 years, s = 0.4) were 42 boys and 26 girls who completed the study assessments on two occasions separated by one week. The following tests were conducted: bioelectrical impedance analysis (BIA) to calculate percent body fat, leg dynamometer, 90° push-up, 7-stage sit-up, and wall squat tests. Intra-class correlation (ICC), paired samples t-tests, and typical error expressed as a coefficient of variation were calculated. The mean percent body fat intra-class correlation coefficient was similar for boys (ICC = 0.95) and girls (ICC = 0.93), but the mean coefficient of variation was considerably higher for boys than girls (22.2% vs. 12.2%). The boys' coefficients of variation for the tests of muscular fitness ranged from 9.0% for the leg dynamometer test to 26.5% for the timed wall squat test. The girls' coefficients of variation ranged from 17.1% for the sit-up test to 21.4% for the push-up test. Although the BIA machine produced reliable estimates of percent body fat, the tests of muscular fitness resulted in high systematic error, suggesting that these measures may require an extensive familiarization phase before the results can be considered reliable.  相似文献   

19.
Do oarsmen have asymmetries in the strength of their back and leg muscles?   总被引：1，自引：0，他引：1  
The aim of this study was to establish whether asymmetry of the strength of the leg and trunk musculature is more prominent in rowers than in controls. Nineteen oarsmen and 20 male controls matched for age, height and body mass performed a series of isokinetic and isometric strength tests on an isokinetic dynamometer. These strength tests focused on the trunk and leg muscles. Comparisons of strength were made between and within groups for right and left symmetry patterns, hamstring: quadriceps ratios, and trunk flexor and extensor ratios. The results revealed no left and right asymmetries in either the knee extensor or flexor strength parameters (including both isometric and isokinetic measures). Knee extensor strength was significantly greater in the rowing population, but knee flexor strength was similar between the two groups. No difference was seen between the groups for the hamstring: quadriceps strength ratio. In the rowing population, stroke side had no influence on leg strength. No differences were observed in the isometric strength of the trunk flexors and extensors between groups, although EMG activity was significantly higher in the rowing population. Patterns of asymmetry of muscle activity were observed between the left and right erector spinae muscles during extension, which was significantly related to rowing side (P < 0.01). These observations could be related to the high incidence of low back pain in oarsmen.  相似文献   

20.
Abstract

This study analysed the first stance phase joint kinetics of three elite sprinters to improve the understanding of technique and investigate how individual differences in technique could influence the resulting levels of performance. Force (1000 Hz) and video (200 Hz) data were collected and resultant moments, power and work at the stance leg metatarsal-phalangeal (MTP), ankle, knee and hip joints were calculated. The MTP and ankle joints both exhibited resultant plantarflexor moments throughout stance. Whilst the ankle joint generated up to four times more energy than it absorbed, the MTP joint was primarily an energy absorber. Knee extensor resultant moments and power were produced throughout the majority of stance, and the best-performing sprinter generated double and four times the amount of knee joint energy compared to the other two sprinters. The hip joint extended throughout stance. Positive hip extensor energy was generated during early stance before energy was absorbed at the hip as the resultant moment became flexor-dominant towards toe-off. The generation of energy at the ankle appears to be of greater importance than in later phases of a sprint, whilst knee joint energy generation may be vital for early acceleration and is potentially facilitated by favourable kinematics at touchdown.  相似文献   

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