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1.
Abstract

The purpose of this study was to determine the influence of lumbar spine extension and erector spinae muscle activation on vertical jump height during maximal squat jumping. Eight male athletes performed maximal squat jumps. Electromyograms of the erector spinae were recorded during these jumps. A simulation model of the musculoskeletal system was used to simulate maximal squat jumping with and without spine extension. The effect on vertical jump height of changing erector spinae strength was also tested through the simulated jumps. Concerning the participant jumps, the kinematics indicated a spine extension and erector spinae activation. Concerning the simulated jumps, vertical jump height was about 5.4 cm lower during squat jump without trunk extension compared to squat jump. These results were explained by greater total muscle work during squat jump, more especially by the erector spinae work (+119.5 J). The erector spinae may contribute to spine extension during maximal squat jumping. The simulated jumps confirmed this hypothesis showing that vertical jumping was decreased if this muscle was not taken into consideration in the model. Therefore it is concluded that the erector spinae should be considered as a trunk extensor, which enables to enhance total muscle work and consequently vertical jump height.  相似文献   

2.
包蕾  刘卉  高维纬 《中国体育科技》2020,(2):39-45,F0003
目的:描述艺术体操运动员在日常状况下和完成专项动作时脊柱异常的表现及左右对称性,探讨与之相关的因素。方法:以9名艺术体操运动员为研究对象,进行站立位脊柱X光片拍摄,获得脊柱额状面和矢状面的弯曲方向和角度;使用三维摄像方法定量评价运动员完成后搬腿动作和侧搬腿动作时的脊柱活动幅度;运用后伸肌群和双侧屈肌群测试系统对运动员的坐姿躯干后伸和双侧侧屈等长收缩力量进行测试。比较躯干活动幅度和躯干肌肉力量的左右对称性,比较不同脊柱侧凸方向间躯干活动差异。检验脊柱弯曲角度与躯干活动特征的相关性。结果:后搬左侧腿时的活动幅度显著小于后搬右侧腿(P<0.01),对应躯干向左扭转的幅度显著大于向右扭转幅度(P<0.05)。侧搬腿时躯干活动幅度越大对应的躯干扭转角度越大。胸曲角度与右侧搬腿活动幅度角存在正相关(P<0.05),与右侧搬腿躯干扭转角之间为显著负相关(P<0.05),腰曲角度与左侧搬腿活动幅度角之间存在显著正相关(P<0.05),与右侧搬腿躯干扭转角之间存在显著负相关(P<0.05)。肌肉力量方面,胸曲角度越大,3个位置躯干后伸力矩峰值越小。侧屈力量上,运动员绝大多数角度下的右屈力量显著大于左屈力量。胸曲角度、腰°曲角度分°别与不同躯干侧屈角度下右屈力矩峰值存在显著负相关。腰曲角度与左屈0、15°、30和右屈15°位置的躯干左屈力矩峰值存在显著负相关。结论:艺术体操运动员躯干两侧活动度和肌肉力量存在不对称,后伸幅度左侧大于右侧,侧屈肌力右侧大于左侧;但这种不对称与脊柱额状面上异常弯曲无明显关系;集中于躯干右侧和躯干后伸动作的训练,可能是导致胸曲变直的原因。  相似文献   

3.
Due to anecdotal reports of back pain during a 12-minute rotational bridge test by uniformed services, the level of fatigue leading to possible back pain and or injury was investigated. We hypothesised a high level of fatigue due to diminishing core muscle activation. Nineteen highly trained uniformed service members were measured by surface electromyography of the rectus abdominis, external oblique, internal oblique, lumbar erector spinae, thoracic erector spinae and latissimus dorsi. Average rectified electromyography amplitude (AEMG) and median power frequency were analysed to determine activation and fatigue. All AEMG were normalised and expressed as a percentage of maximal voluntary isometric contraction (%MVIC). Significant increases in AEMG were observed over the test duration for the rectus abdominis (+19.5%MVIC), external oblique (+18.0%MVIC) and internal oblique (+23.2%MVIC) during the prone position; and for the external oblique (+21.8%MVIC) when bracing on the measurement side (all, p < 0.05). No significant changes in median power frequency were observed (all, p > 0.05). Combining prone and side bridge positions is a reasonable measure of anterior, posterior and lateral trunk musculature. Muscular fatigue remained low throughout making this a safe assessment in trained individuals.  相似文献   

4.
This investigation examined effects of two exercise modes (barbell, BB; bodyweight suspension, BWS) on muscle activation, resistance load, and fatigue. During session one, nine resistance-trained males completed an elbow flexion one-repetition maximum (1RM). During sessions two and three, subjects completed standing biceps curls to fatigue at 70% 1RM utilizing a randomized exercise mode. Surface electromyography (sEMG) recorded muscle activation of the biceps brachii, triceps brachii, anterior deltoid, posterior deltoid, rectus abdominis, and erector spinae. BWS resistance load was measured using a force transducer. Standing maximal voluntary isometric contractions of the elbow flexors recorded at 90° were used to determine the isometric force decrement and rate of fatigue (ROF) during exercise. sEMG and resistance load data were divided into 25% contraction duration bins throughout the concentric phase. BWS resulted in a 67.7?±?7.4% decline in resistance load throughout the concentric phase (p?≤?0.05). As a result, BB elicited higher mean resistance loads (31.4?±?4.0?kg) and biceps brachii sEMG (84.7?±?27.8% maximal voluntary isometric contractions, MVIC) compared with BWS (20.4?±?3.4?kg, 63.4?±?21.6% MVIC). No difference in rectus abdominis or erector spinae sEMG was detected between exercise modes. Isometric force decrement was greater during BWS (?21.7?±?7.0?kg) compared with BB (?14.9?±?4.7?kg); however, BB (?3.0?±?0.8?kg/set) resulted in a steeper decline in ROF compared with BWS (?1.7?±?0.6?kg/set). The variable resistance loading and greater isometric force decrement observed suggest that select BWS exercises may resemble variable resistance exercise more than previously considered.  相似文献   

5.
Abstract

This study aimed to investigate the contributions of kinetic and kinematic parameters to inter-individual variation in countermovement jump (CMJ) performance. Two-dimensional kinematic data and ground reaction forces during a CMJ were recorded for 18 males of varying jumping experience. Ten kinetic and eight kinematic parameters were determined for each performance, describing peak lower-limb joint torques and powers, concentric knee extension rate of torque development and CMJ technique. Participants also completed a series of isometric knee extensions to measure the rate of torque development and peak torque. CMJ height ranged from 0.38 to 0.73 m (mean 0.55 ± 0.09 m). CMJ peak knee power, peak ankle power and take-off shoulder angle explained 74% of this observed variation. CMJ kinematic (58%) and CMJ kinetic (57%) parameters explained a much larger proportion of the jump height variation than the isometric parameters (18%), suggesting that coachable technique factors and the joint kinetics during the jump are important determinants of CMJ performance. Technique, specifically greater ankle plantar-flexion and shoulder flexion at take-off (together explaining 58% of the CMJ height variation), likely influences the extent to which maximal muscle capabilities can be utilised during the jump.  相似文献   

6.
The objective of this study was to determine whether sprint performance is related to the mechanical (elongation - force relationship of the tendon and aponeurosis, muscle strength) and morphological (fascicle length, pennation angle, muscle thickness) properties of the quadriceps femoris and triceps surae muscle - tendon units. Two groups of sprinters (slow, n = 11; fast, n = 17) performed maximal isometric knee extension and plantar flexion contractions on a dynamometer at 11 different muscle - tendon unit lengths. Elongation of the tendon and aponeurosis of the gastrocnemius medialis and the vastus lateralis was measured using ultrasonography. We observed no significant differences in maximal joint moments at the ankle and knee joints or morphological properties of the gastrocnemius medialis and vastus lateralis between groups (P > 0.05). The fast group exhibited greater elongation of the vastus lateralis tendon and aponeurosis at a given tendon force, and greater maximal elongation of the vastus lateralis tendon and aponeurosis during maximum voluntary contraction (P < 0.05). Furthermore, maximal elongation of the vastus lateralis tendon and aponeurosis showed a significant correlation with 100-m sprint times (r = -0.567, P = 0.003). For the elongation - force relationship at the gastrocnemius medialis tendon and aponeurosis, the two groups recorded similar values. It is suggested that the greater elongation of the vastus lateralis tendon and aponeurosis of the fast group benefits energy storage and return as well as the shortening velocity of the muscle - tendon unit.  相似文献   

7.
Introduction: Adolescent fast bowlers are prone to sustaining lumbar injuries. Numerous components have been identified as contributing factors; however, there is limited empirical evidence outlining how the muscles of the lumbopelvic region, which play a vital role in stabilising the spine, function during the bowling action and the influence of such activation on injuries in the fast bowler. Methods: Surface electromyography was utilised to measure the function of the lumbar erector spinae, lumbar multifidus, gluteus medius and gluteus maximus muscles bilaterally during the fast bowling action in a group of 35 cricket fast bowlers aged 12–16 years. Results: Two prominent periods of activation occurred in each of the muscles examined. The period of greatest mean activation in the erector spinae and multifidus occurred near back foot contact (BFC) and within the post-ball-release (BR) phase. The period of greatest mean activation for the gluteus medius and gluteus maximus occurred during phases of ipsilateral foot contact. Discussion: The greatest periods of muscle activation in the paraspinal and gluteal muscles occurred at times where vertical forces were high such as BFC, and in the phases near BR where substantial shear forces are present. Conclusion: The posterior muscles within the lumbopelvic region appear to play a prominent role during the bowling action, specifically when compressive and shear forces are high. Further research is required to substantiate these findings and establish the role of the lumbopelvic muscles in the aetiology of lumbar injury in the cricket fast bowler.  相似文献   

8.
Abstract

Aim of the study was to compare the effects of unilateral eccentric-only training using constant velocity vs. constant external load. Forty-seven participants were randomized in isokinetic (IK), dynamic constant external resistance (DCER) unilateral eccentric training or control groups. Knee extension 1RM and isometric, eccentric and concentric knee extensors peak torque, as well as changes in vastus lateralis fascicle pennation angle, fascicle length, muscle thickness, and quadriceps fat-free mass were measured. Both IK and DCER training consisted in 5?×?8 eccentric-only repetitions, 2d/w, for 6 weeks. IK and DCER training sessions were matched for total volume. After training, both IK and DCER similarly increased 1RM (respectively, +4.4?kg, CI95% 1.8–7.0 and +5.5?kg, CI95% 3.3–7.9), isometric (respectively, +34.5?N/m, CI95% 23.0–45.9 and +15.8, CI95% 5.4–26.2) and concentric peak torque (respectively, +17.0?N/m, CI95% 6.6 to +27.4 and 12.2 CI95% 2.8–21.7). IK increased eccentric peak torque significantly more than DCER (respectively, +84.2?N/m, CI95% 66.3–102.1 and +38.2?N/m, CI95% 21.9–54.4). Both IK and DCER similarly increased fascicle length (respectively, +14.7?mm, CI95% 5.4–24.0 and +14.4?mm, CI95% 5.4–23.3) and muscle thickness (respectively, +3.3?mm, CI95% 1.5–5.1, and +4.1?mm, CI95% 2.5–5.7). Matching the training volume resulted in similar adaptations comparing eccentric-only IK or DCER resistance training. Both in rehabilitation and in training practice, the use of easily available gym devices can be a good substitute for expensive and often unavailable IK devices.  相似文献   

9.
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10.
ABSTRACT

This study investigated the effects of maturity status on knee extensor torque and vastus lateralis architecture of young soccer players. Thirty-four males aged 13–18 years were divided into two groups: pubescent (PUB, n = 15) and postpubescent (POSP, n = 19). Torque by angle interaction was established for absolute [F(2.649, 84.771) = 9.066, p < 0.05] and relative to body mass [F(2.704, 86.533) = 4.050, p < 0.05] isometric torque with the POSP group showing greater values. Muscle volume torque-angle relationship was similar between groups. Absolute, relative to body mass, and relative to muscle volume concentric and eccentric torque-velocity relationship showed a non-significant interaction but a significant group effect in favour the POSP group for absolute and concentric torque relative to body mass. Torque-angle and torque-velocity relationship normalized by body mass allometric exponents showed a non-significant interactions and group effects. Muscle thickness (3.6 ± 0.6 vs. 3.8 ± 0.6 cm), fascicle length (8.3 ± 1.4 vs. 8.9 ± 1.6 cm) and pennation angle (15.0 ± 2.3 vs. 14.3 ± 3.2 degrees) was similar between PUB and POSP groups, respectively. Maturity status did not show a significant effect on muscle architecture and on isometric and dynamic torques when allometrically normalized.  相似文献   

11.
The purpose of this study was to investigate the effects of series elasticity on the torque-angle relationship of the knee extensors in vivo. Forty-two men volunteered to take part in the present study. The participants performed maximal voluntary isometric contractions at eight knee-joint angles (40, 50, 60, 70, 80, 90, 100, 110 degrees). The elongation of the tendon and aponeurosis of the vastus lateralis muscle was directly measured by ultrasonography, while the participants performed ramp isometric knee extensions to the voluntary maximum at 800 of knee angle. There was no significant difference in the torque value between 50 degrees and 100 degrees, although there was variation in the shape of the "torque-angle" relationship. The variability in the torque-angle curve was not affected by the activation level of agonist and antagonist muscles and the moment arm length. The ratio of torque at 1000 compared to that at 50 degrees was significantly (r(2) = 18-23 %) correlated to the maximal elongation and strain (to initial length) of the tendon structures. These results suggest that increased compliance of tendon structures of the knee extensors may contribute to variations in the torque-angle curves of the knee extensors.  相似文献   

12.
Purpose: The present study aimed to investigate whether or not eccentric-only training induced different sex-related adaptations in vastus lateralis muscle architecture and knee extensors strength. Methods: Thirteen healthy women and 13 healthy men were recruited. Vastus lateralis pennation angle, fascicle length, and muscle thickness, as well as knee extensors eccentric, isometric, and concentric peak torque and one-repetition maximum (1RM) were measured. Both women and men underwent a unilateral iso-load knee-extension eccentric-only training with 120% of the concentric 1RM, consisting of 4 sets × 10 repetitions twice a week for a total of 8 weeks. Results: Pennation angle increased in women (+ 14%, 95% CI [10, 17], effect size [ES] = 1.54) but not in men (+ 5%, 95% CI [?1, 11], ES = 0.28), while fascicle length increased in both women (+ 7%, 95% CI [4, 10], ES = 1.02) and men (+ 12%, 95% CI [8, 16], ES = 1.82) and muscle thickness increased in women (+ 13%, 95% CI [8, 18], ES = 1.11) and men (+ 11%, 95% CI [7, 15], ES = 0.89). In both women and men, eccentric (18%, 95% CI [11, 25], ES = 0.96, and 16%, 95% CI [9, 22], ES = 0.82, respectively), isometric (17%, 95% CI [11, 23], ES = 0.53, and 17%, 95% CI [10, 24], ES = 0.62), concentric (12%, 95% CI [7, 16], ES = 0.49, and 9%, 95% CI [5, 13], ES = 0.42) peak torque and 1RM (10%, 95% CI [6, 14], ES = 0.53, and 10%, 95% CI [5, 15], ES = 0.50) similarly increased after the intervention. Conclusions: This study showed that the adaptations in strength are not sex-dependent, but the increases in pennation angle only in women suggest that the changes in muscle architecture may depend on sex.  相似文献   

13.
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14.
This study was undertaken to examine the acute effect of interferential current on mechanical pain threshold and isometric peak torque after delayed onset muscle soreness induction in human hamstrings. Forty-one physically active healthy male volunteers aged 18-33 years were randomly assigned to one of two experimental groups: interferential current group (n = 21) or placebo group (n = 20). Both groups performed a bout of 100 isokinetic eccentric maximal voluntary contractions (10 sets of 10 repetitions) at an angular velocity of 1.05 rad · s(-1) (60° · s(-1)) to induce muscle soreness. On the next day, volunteers received either an interferential current or a placebo application. Treatment was applied for 30 minutes (4 kHz frequency; 125 μs pulse duration; 80-150 Hz bursts). Mechanical pain threshold and isometric peak torque were measured at four different time intervals: prior to induction of muscle soreness, immediately following muscle soreness induction, on the next day after muscle soreness induction, and immediately after the interferential current and placebo application. Both groups showed a reduction in isometric torque (P < 0.001) and pain threshold (P < 0.001) after the eccentric exercise. After treatment, only the interferential current group showed a significant increase in pain threshold (P = 0.002) with no changes in isometric torque. The results indicate that interferential current was effective in increasing hamstrings mechanical pain threshold after eccentric exercise, with no effect on isometric peak torque after treatment.  相似文献   

15.
The aim of this study was to identify how changes in the stability conditions of a back squat affect maximal loads lifted and erector spinae muscle activity. Fourteen male participants performed a Smith Machine (SM) squat, the most stable condition, a barbell back (BB) squat, and Tendo-destabilizing bar (TBB) squat, the least stable condition. A one repetition max (1-RM) was established in each squat condition, before electromyography (EMG) activity of the erector spinae was measured at 85% of 1-RM. Results indicated that the SM squat 1-RM load was significantly (p = 0.006) greater (10.9%) than the BB squat, but not greater than the TBB squat. EMG results indicated significantly greater (p < 0.05) muscle activation in the TBB condition compared to other conditions. The BB squat produced significantly greater (p = 0.036) EMG activity compared to the SM squat. A greater stability challenge applied to the torso seems to increase muscle activation. The maximum loads lifted in the most stable and unstable squats were similar. However, the lift with greater stability challenge required greatest muscle activation. The implications of this study may be important for training programmes; if coaches wish to challenge trunk stability, while their athletes lift maximal loads designed to increase strength.  相似文献   

16.
BackgroundFemales are typically less fatigable than males during sustained isometric contractions at lower isometric contraction intensities. This sex difference in fatigability becomes more variable during higher intensity isometric and dynamic contractions. While less fatiguing than isometric or concentric contractions, eccentric contractions induce greater and longer lasting impairments in force production. However, it is not clear how muscle weakness influences fatigability in males and females during sustained isometric contractions.MethodsWe investigated the effects of eccentric exercise-induced muscle weakness on time to task failure (TTF) during a sustained submaximal isometric contraction in young (18–30 years) healthy males (n = 9) and females (n = 10). Participants performed a sustained isometric contraction of the dorsiflexors at 35° plantar flexion by matching a 30% maximal voluntary contraction (MVC) torque target until task failure (i.e., falling below 5% of their target torque for ≥2 s). The same sustained isometric contraction was repeated 30 min after 150 maximal eccentric contractions. Agonist and antagonist activation were assessed using surface electromyography over the tibialis anterior and soleus muscles, respectively.ResultsMales were ∼41% stronger than females. Following eccentric exercise both males and females experienced an ∼20% decline in maximal voluntary contraction torque. TTF was ∼34% longer in females than males prior to eccentric exercise-induced muscle weakness. However, following eccentric exercise-induced muscle weakness, this sex-related difference was abolished, with both groups having an ∼45% shorter TTF. Notably, there was ∼100% greater antagonist activation in the female group during the sustained isometric contraction following exercise-induced weakness as compared to the males.ConclusionThis increase in antagonist activation disadvantaged females by decreasing their TTF, resulting in a blunting of their typical fatigability advantage over males.  相似文献   

17.
The aims of this study were to examine the acute effects of static stretching on peak torque, work, the joint angle at peak torque, acceleration time, isokinetic range of motion, mechanomyographic amplitude, and electromyographic amplitude of the rectus femoris during maximal concentric isokinetic leg extensions at 1.04 and 5.23 rad x s(-1) in men and women. Ten women (mean +/- s: age 23.0 +/- 2.9 years, stature 1.61 +/- 0.12 m, mass 63.3 +/- 9.9 kg) and eight men (age 21.4 +/- 3.0 years, stature 1.83 +/- 0.11 m, mass 83.1 +/- 15.2 kg) performed maximal voluntary concentric isokinetic leg extensions at 1.04 and 5.23 rad x s(-1). Following the initial isokinetic tests, the dominant leg extensors were stretched using four static stretching exercises. After the stretching, the isokinetic tests were repeated. Peak torque, acceleration time, and electromyographic amplitude decreased (P< or = 0.05) from pre- to post-stretching at 1.04 and 5.23 rad . s(-1); there were no changes (P > 0.05) in work, joint angle at peak torque, isokinetic range of motion, or mechanomyographic amplitude. These findings indicate no stretching-related changes in the area under the angle - torque curve (work), but a significant decrease in peak torque, which suggests that static stretching may cause a "flattening" of the angle - torque curve that reduces peak strength but allows for greater force production at other joint angles. These findings, in conjunction with the increased limb acceleration rates (decreased acceleration time) observed in the present study, provide tentative support for the hypothesis that static stretching alters the angle - torque relationship and/or sarcomere shortening velocity.  相似文献   

18.
Abstract

The objective of this study was to determine whether sprint performance is related to the mechanical (elongation – force relationship of the tendon and aponeurosis, muscle strength) and morphological (fascicle length, pennation angle, muscle thickness) properties of the quadriceps femoris and triceps surae muscle – tendon units. Two groups of sprinters (slow, n = 11; fast, n = 17) performed maximal isometric knee extension and plantar flexion contractions on a dynamometer at 11 different muscle – tendon unit lengths. Elongation of the tendon and aponeurosis of the gastrocnemius medialis and the vastus lateralis was measured using ultrasonography. We observed no significant differences in maximal joint moments at the ankle and knee joints or morphological properties of the gastrocnemius medialis and vastus lateralis between groups (P > 0.05). The fast group exhibited greater elongation of the vastus lateralis tendon and aponeurosis at a given tendon force, and greater maximal elongation of the vastus lateralis tendon and aponeurosis during maximum voluntary contraction (P < 0.05). Furthermore, maximal elongation of the vastus lateralis tendon and aponeurosis showed a significant correlation with 100-m sprint times (r = ?0.567, P = 0.003). For the elongation – force relationship at the gastrocnemius medialis tendon and aponeurosis, the two groups recorded similar values. It is suggested that the greater elongation of the vastus lateralis tendon and aponeurosis of the fast group benefits energy storage and return as well as the shortening velocity of the muscle – tendon unit.  相似文献   

19.
The length-tension relationship of muscle contraction is well documented in adults. However, research on this relationship in children has been limited. The aim of this study was to compare differences in the torque-joint angle relationship of the quadriceps muscle in children and adults. Eight boys aged 8-10 years and eight men aged 20-26 years performed two maximal voluntary isometric contractions at six knee joint angles (20 degrees, 40 degrees, 60 degrees, 80 degrees, 90 degrees, 100 degrees). The mean of the two trials was used as the performance measure. Both groups demonstrated an expected increase in relative torque as the joint angle increased (P< 0.05). The men produced significantly greater relative torque at 20 degrees, 40 degrees and 60 degrees knee flexion (P < 0.05). The percentage of maximal torque at these angles for the men and boys respectively were: 35.2+/-4.3 vs 15.2+/-12%, 63.6+/-9.1 vs 51.8+/-16.8% and 93.6+/-6.5 vs 84.4+/-14.4%. There were no group differences at 80 degrees or 90 degrees. Peak torque was attained at 80 degrees in men, but decreased significantly (P< 0.05) at 90 degrees and 100 degrees. For boys, peak torque was attained at joint angles of 80 degrees and 90 degrees. The reduction in peak torque at 100 degrees was not statistically significant, but the relative torque at this angle was lower in men than in boys (77.9+/-13.7 vs 87.1+/-10.4%; P< 0.05). In conclusion, the relationship between torque and joint angle appears to be affected by age.  相似文献   

20.
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   

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