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1.
Abstract

This study investigated the influence of dehydration during soccer-type intermittent exercise on isokinetic and isometric muscle function. Eight soccer players performed two 90-min high-intensity intermittent shuttle-running trials without (NF) or with (FL) fluid ingestion (5 ml · kg?1 before and 2 ml · kg?1 every 15 min). Isokinetic and isometric strength and muscular power of knee flexors and knee extensors were measured pre-exercise, at half-time and post-exercise using isokinetic dynamometry. Sprint performance was monitored throughout the simulated-soccer exercise. Isokinetic knee strength was reduced at faster (3.13 rad · s?1; P = 0.009) but not slower (1.05 rad · s?1; P = 0.063) contraction speeds with exercise; however, there was no difference between FL and NF. Peak isometric strength of the knee extensors (P = 0.002) but not the knee flexors (P = 0.065) was significantly reduced with exercise with no difference between FL and NF. Average muscular power was reduced over time at both 1.05 rad · s?1 (P = 0.01) and 3.14 rad · s?1 (P = 0.033) but was not different between FL and NF. Mean 15-m sprint time increased with duration of exercise (P = 0.005) but was not different between FL and NF. In summary, fluid ingestion during 90 min of soccer-type exercise was unable to offset the reduction in isokinetic and isometric strength and muscular power of the knee extensors and flexors.  相似文献   

2.
Abstract

We compared starters and non-starters for various isokinetic strength variables in elite women’s soccer players. A convenience sample of 10 starters (mean ± s; age = 20 ± 2 years; height = 170 ± 4 cm; body mass = 65 ± 5 kg) and 7 non-starters (age = 20 ± 1 years; height = 164 ± 3 cm; body mass = 63 ± 4 kg) performed maximal voluntary muscle actions of the leg extensors (concentric) and flexors (eccentric) on an isokinetic dynamometer in order to measure concentric peak torque for the leg extensors, eccentric peak torque for the leg flexors, and the functional hamstrings:quadriceps (H:Q) ratio at 1.047 rad · s-1 and 4.189 rad · s-1 concentric peak torque for the leg extensors was not different between starters and non-starters. However, it was greater at 1.047 rad · s-1 than at 4.189 rad · s-1 in both groups. Eccentric peak torque for the leg flexors was greater for the starters versus non-starters at 4.189 rad · s-1. Eccentric strength of the leg flexors at fast movement velocities may be used as an effective physiological profile and may discriminate between playing status in elite women’s soccer players.  相似文献   

3.
Eccentric contractions that provide spring energy can also cause muscle damage. The aim of this study was to explore leg and vertical stiffness following muscle damage induced by an eccentric exercise protocol. Twenty active males completed 60 minutes of backward-walking on a treadmill at 0.67 m/s and a gradient of ? 8.5° to induce muscle damage. Tests were performed immediately before; immediately post; and 24, 48, and 168 hours post eccentric exercise. Tests included running at 3.35 m/s and hopping at 2.2 Hz using single- and double-legged actions. Leg and vertical stiffness were measured from kinetic and kinematic data, and electromyography (EMG) of five muscles of the preferred limb were recorded during hopping. Increases in pain scores (over 37%) occurred post-exercise and 24 and 48 hours later (p < 0.001). A 7% decrease in maximal voluntary contraction occurred immediately post-exercise (p = 0.019). Changes in knee kinematics during single-legged hopping were observed 168 hours post (p < 0.05). No significant changes were observed in EMG, creatine kinase activity, leg, or vertical stiffness. Results indicate that knee mechanics may be altered to maintain consistent levels of leg and vertical stiffness when eccentric exercise-induced muscle damage is present in the lower legs.  相似文献   

4.
It is currently unclear how football participation affects knee-joint muscle balance, which is widely considered a risk factor for hamstrings injury. This study compared the angle-specific functional hamstring-to-quadriceps (H:Q) ratio (hamstrings eccentric torque as a ratio of quadriceps concentric torque at the same knee-joint angle) of football players with recreationally active controls. Ten male footballers and 14 controls performed maximal voluntary isometric and isovelocity concentric and eccentric contractions (60, 240 and 400° s?1) of the knee extensors and flexors. Gaussian fitting to the raw torque values was used to interpolate torque values for knee-joint angles of 100–160° (60° s?1), 105–160° (240° s?1) and 115–145° (400° s?1). The angle-specific functional H:Q ratio was calculated from the knee flexors eccentric and knee extensors concentric torque at the same velocity and angle. No differences were found for the angle-specific functional H:Q ratio between groups, at any velocity. Quadriceps and hamstrings strength relative to body mass of footballers and controls was similar for all velocities, except concentric knee flexor strength at 400° s?1 (footballers +40%; P < 0.01). In previously uninjured football players, there was no intrinsic muscle imbalance and therefore the high rate of hamstring injuries seen in this sport may be due to other risk factors and/or simply regular exposure to a high-risk activity.  相似文献   

5.
Fatigue represents a reduction in the capability of muscle to generate force. The aim of the present study was to establish the effects of exercise that simulates the work rate of competitive soccer players on the strength of the knee extensors and knee flexors. Thirteen amateur soccer players (age 23.3±3.9 years, height 1.78±0.05?m, body mass 74.8±3.6?kg; mean±s) were tested during the 2000–2001 soccer season. Muscle strength of the quadriceps and hamstrings was measured on an isokinetic dynamometer. A 90?min soccer-specific intermittent exercise protocol, incorporating a 15?min half-time intermission, was developed to provide fatiguing exercise corresponding in work rate to a game of soccer. The exercise protocol, performed on a programmable motorized treadmill, consisted of the different intensities observed during soccer match-play (e.g. walking, jogging, running, sprinting). Muscle strength was assessed before exercise, at half-time and immediately after exercise. A repeated-measures analysis of variance showed significant reductions (P?<0.001) in peak torque for both the quadriceps and hamstrings at all angular velocities (concentric: 1.05, 2.09, 5.23 rad?·?s?1; eccentric: 2.09 rad?·?s?1). The peak torque of the knee extensors (KE) and knee flexors (KF) was greater before exercise [KE: 232±37, 182±34, 129±27, 219±41?N?·?m at 1.05, 2.09 and 5.23 rad?·?s?1 (concentric) and 2.09 rad?·?s?1 (eccentric), respectively; KF: 126±20, 112±19, 101±16, 137±23?N?·?m] than at half-time (KE: 209±45, 177±35, 125±36, 214±43?N?·?m; KF: 114±31, 102±20, 92±15, 125±25?N?·?m) and greater at half-time than after exercise (KE: 196±43, 167±35, 118±24, 204±43?N?·?m; KF: 104±25, 95±21, 87±13, 114±27?N?·?m). For the hamstrings?:?quadriceps ratio, significant changes were found (P?<0.05) for both legs, the ratio being greater before than after exercise. For fast?:?slow speed and left?:?right ratios, no significant changes were found. We conclude that there is a progressive reduction in muscle strength that applies across a range of functional characteristics during exercise that mimics the work rate in soccer.  相似文献   

6.
Abstract

The purpose of this study was to investigate the eccentric torque–velocity and power–velocity relationships of the elbow flexors. Forty recreationally trained individuals (20 men, 20 women) performed maximal eccentric actions at each of five different velocities (1.04 rad · s?1, 2.09 rad · s?1, 3.14 rad · s?1, 4.18 rad · s?1, and 5.23 rad · s?1, in random order) and maximal isometric actions on a Biodex isokinetic dynamometer. A 2×6 (sex×velocity) mixed-factor repeated-measures analysis of variance (ANOVA) was used to assess peak elbow flexor torque during the eccentric and isometric actions. There was no interaction, but there were significant main effects for sex and velocity. Pairwise comparisons demonstrated that values for men were significantly (P<0.05) higher than those for women at all speeds. Furthermore, torques for both sexes were significantly less at 3.14 rad · s?1 (men: 103.94±28.28 N · m; women: 49.24±11.69 N · m) than at 4.18 rad · s?1 (men: 106.39±30.23 N · m; women: 52.77±11.31 N · m) and 5.23 rad · s?1 (men: 108.75±28.59 N · m; women: 53.3±11.67 N · m), while isometric torque was significantly less than at all other speeds (men: 98.66±28.0 N · m; women: 45.25±11.15 N · m). A 2×5 (sex×velocity) mixed-factor repeated-measures ANOVA was used to assess peak eccentric elbow flexor power. There were significant main effects for sex and velocity. Pairwise comparisons demonstrated that values for men were significantly higher than those for women at all speeds. Pairwise comparisons for velocity indicated that peak eccentric power increased across all speeds from 1.04 rad · s?1 (men: 110.44±32.56 W; women 54.36±13.05 W) to 5.23 rad · s?1 (men: 569.46±149.73 W; women: 279.10±61.10 W). These results demonstrate that an increase in velocity had little or no effect on eccentric elbow flexor torque, while eccentric elbow flexor power increased significantly with increases in velocity.  相似文献   

7.
Runners often experience delayed onset muscle soreness (DOMS), especially of the knee extensors, following prolonged running. Sagittal knee joint biomechanics are altered in the presence of knee extensor DOMS but it is unclear how muscle soreness affects lower limb biomechanics in other planes of motion. The purpose of this study was to assess the effects of knee extensor DOMS on three-dimensional (3D) lower limb biomechanics during running. Thirty-three healthy men (25.8?±?6.8 years; 84.1?±?9.2?kg; 1.77?±?0.07?m) completed an isolated eccentric knee extensor damaging protocol to elicit DOMS. Biomechanics of over-ground running at a set speed of 3.35?m?s?1±5% were measured before eccentric exercise (baseline) and, 24?h and 48?h following exercise in the presence of knee extensor DOMS. Knee flexion ROM was reduced at 48?h (P?=?0.01; d?=?0.26), and peak knee extensor moment was reduced at 24?h (P?=?0.001; d?=?0.49) and 48?h (P?<?0.001; d?=?0.68) compared to baseline. Frontal and transverse plane biomechanics were unaffected by the presence of DOMS (P?>?0.05). Peak positive ankle and knee joint powers and, peak negative knee joint power were all reduced from baseline to 24?h and 48?h (P?<?0.05). These findings suggest that knee extensor DOMS greatly influences sagittal knee joint angular kinetics and, reduces sagittal power production at the ankle joint. However, knee extensor DOMS does not affect frontal and transverse plane lower limb joint biomechanics during running.  相似文献   

8.
Abstract

Despite the widespread use of isokinetic eccentric muscle endurance protocols, no research has examined the absolute and relative reliability of such tests. The aim of this study was to examine the reliability of an isokinetic eccentric knee muscle endurance task. Fifteen healthy untrained males volunteered to take part in the study and written informed consent was obtained. The procedures received approval from the University Research Ethics Committee. Participants visited the laboratory on three separate occasions: 2 weeks before testing to familiarize them with the experimental procedures, and on two separate occasions, 2 weeks apart and at the same time of day. Isokinetic eccentric knee extension and flexion movements of the dominant limb were performed using a calibrated dynamometer (Biodex System 3). Range of motion during testing was set using voluntary maximal full extension (0 rad) to 1.57 rad of knee flexion and testing was conducted at 1.56 rad · s?1. Participants performed four maximal efforts to determine maximal peak torque. After 2 min rest, participants completed the all-out endurance test of 50 continuous eccentric repetitions. Data were gravity corrected and windowed to only include constant velocity periods. Repeated-measures analyses of variance were used to examine differences in maximal peak extension and flexion torque and the maximal torque measurement recorded during the endurance test. Absolute and relative reliability of the torque fatigue index, work fatigue index, and total work were assessed through calculation of intra-class correlation coefficients, coefficients of variation, and absolute 95% limits of agreement using the methods described by Bland and Altman (1986). Differences between the strength test and the endurance trial for peak torque were found to be non-significant for both quadriceps (323 vs. 323 N · m) and hamstrings (183 vs. 178 N · m). The intra-class correlation coefficients revealed significant (P<0.05) positive moderate to strong correlations (r=0.44–0.94) across repeated trials for all parameters except hamstring torque fatigue (P=0.11) and hamstring work fatigue index (P=0.08). Coefficients of variation ranged from 6% to 48% and were large for the work fatigue index and torque fatigue index but acceptable for total work for both the extensors and flexors. The 95% limits of agreement indicated systematic bias in repeated trials for both the work fatigue index and torque fatigue index for extensors and flexors, ranging from ?3% to ?10%, with less fatigue evident in the second test. There was also systematic bias for total work, with more work being performed during the second than the first test for both extensors and flexors. The random error was large for all variables and there was greater random error in the hamstrings compared with the quadriceps. Together with moderate to strong intra-class correlation coefficients and large coefficients of variation, the data suggest that there is small systematic bias in repeated eccentric muscle actions for both the quadriceps and hamstrings, although the random error was large despite habituation procedures. Therefore, data from an isokinetic eccentric muscle endurance task should be viewed with some caution even when participants receive considerable habituation before assessment.  相似文献   

9.
Kinetics and full body kinematics were measured in ten elite goalkeepers diving to save high and low balls at both sides of the goal, aiming to investigate their starting position, linear and angular momentum, and legs' contribution to end-performance. Our results showed that goalkeepers adopted a starting position with a stance width of 33 ± 1% of leg length, knee flexion angle of 62 ± 18° and hip flexion angle of 63 ± 18°. The contralateral leg contributed more than the ipsilateral leg to COM velocity (p < 0.01), both for the horizontal (2.7 ± 0.1 m·s?1 versus 1.2 ± 0.1 m·s?1) and for the vertical component (3.1 ± 0.3 m·s?1 versus 0.4 ± 0.2 m·s?1). Peak horizontal and peak angular momenta were significantly larger (p < 0.01) for low dives than for high dives with a mean difference of 55 kg·m·s?1 and 9 kg·m2·s?1, respectively. In addition, peak vertical momentum was significantly larger (p < 0.01) for high dives with a mean difference between dive heights of 113 kg·m·s?1. Coaches need to highlight horizontal lateral skills and exercises (e.g. sideward push-off, sideward jumps), with emphasis on pushing-off with the contralateral leg, when training and assessing goalkeeper’s physical performance.  相似文献   

10.
Abstract

The mechanics of cutting movements have been investigated extensively, but few studies have considered the rapid deceleration phase prior to turning which has been linked to muscle damage. This study used accelerometry to examine the influence of turning intensity on the last three steps of a severe turn.

Ten soccer players performed 135° “V” cuts at five different intensities. Resultant decelerations were recorded from a trunk-mounted tri-axial accelerometer. Lower limb kinematics and ground reaction forces (GRF) from the pivot foot-ground contact (FGC) were also monitored.

Average peak trunk decelerations were larger at the two preceding steps (4.37 ± 0.12 g and 4.58 ± 0.11 g) compared to the PIVOT step (4.10 ± 0.09 g). Larger peak joint flexion angular velocities were observed at PRE step (ankle: 367 ± 192 deg.s?1; knee 493 ± 252 deg.s?1) compared to PIVOT step (ankle 255 ± 183 deg.s?1; knee 377 ± 229 deg.s?1). Turn intensity did not influence peak GRF at PIVOT step.

This study highlights the importance of steps prior to turning and their high-frequency loading characteristics. It is suggested that investigations of lower limb loading during turning should include this deceleration phase and not focus solely on pivot FGC.  相似文献   

11.
This study aimed to provide a comprehensive strength-based physiological profile of women’s NCAA Division I basketball and gymnastic athletes; and to make sport-specific comparisons for various strength characteristics of the knee flexor and extensor muscles. A focus on antagonist muscle balance (hamstrings-to-quadriceps ratios, H:Q) was used to elucidate vulnerabilities in these at-risk female athletes. Fourteen NCAA Division I women’s basketball and 13 gymnastics athletes performed strength testing of the knee extensors and flexors. Outcome measures included absolute and relative (body mass normalised) peak torque (PT), rate of torque development at 50, 100, 200 ms (RTD50 etc.) and H:Q ratios of all variables. The basketball athletes had greater absolute strength for all variables except for isokinetic PT at 240°s?1 and isometric RTD50 for the knee extensors. Gymnasts showed ~20% weaker body mass relative concentric PT for the knee flexors at 60 and 120°·s?1, and decreased conventional H:Q ratios at 60 and 240°·s?1 (~15%). These findings suggest that collegiate level gymnastics athletes may be prone to increased ACL injury risk due to deficient knee flexor strength and H:Q strength imbalance. Coaches may use these findings when implementing injury prevention screening and/or for individualised strength training programming centered around an athletes strength-related deficits.  相似文献   

12.
Abstract

This study investigated symptoms of exercise-induced muscle damage following a simulated rugby league game. Ten male participants were assessed before, immediately after (0 h), and 24 and 48 h after the simulated game. Perceived muscle soreness was higher at all time points (P=0.001) and creatine kinase values were increased at 24 h following the simulated game (P=0.001). Peak knee extensor torque at 60 deg · s?1 was reduced up to 48 h (P =0.04) but was unchanged at 240 deg · s?1. Similarly, peak knee flexor torque at 60 deg · s?1 was lower than baseline up to 24 h, while at 240 deg · s?1 it was reduced at 24 h only (P=0.045). Correlations between changes in strength loss of the knee extensors and fat mass to fat-free mass ratio reveleaved no significant relationship between variables (P >0.05). In addition, countermovement jump performance was reduced at 0 and 24 h following the simulated game (P=0.008). Our results suggest that symptoms of exercise-induced muscle damage occur up to 48 h following a simulated rugby league match. Coaches should be cognisant of the large increases in muscle soreness and reductions in slow velocity force generation, and should adapt training accordingly in the 48 h period following a game.  相似文献   

13.
Abstract

Aim: To investigate the effect of different water immersion (WI) treatments on recovery from intermittent shuttle running exercise in comparison to an ecologically relevant control.

Methods: Forty males performed 90 minutes intermittent shuttle running, following which they were assigned to either: (1) 12-min standing WI at 12°C; (2) 12-min standing WI at 35°C; (3) 2-min seated WI at 12°C; (4) an ecologically relevant control consisting of 12 minutes walking at 5 km h?1. Muscle soreness, maximal voluntary contraction (MVC) of the knee flexors and extensors, hop distance, creatine kinase activity and myoglobin concentration were measured before exercise and in the 168 hours following the intervention. Between-group differences, time effects and interaction effects were investigated by mixed-model ANOVA.

Results: The shuttle running exercise induced an increase in muscle soreness (1, 24, 48 and 72 hours post-intervention) creatine kinase activity and myoglobin concentration (post-exercise and 1, 24 and 48 hours post-intervention), and reduced MVC of the knee extensors (11% reduction at 24 hours, remaining reduced at 48 and 72 hours), flexors (24% reduction at 24 hours, remaining reduced at 24, 48, 72 and 168 hours), and hop distance (24 and 48 hours). However, no between-group differences or interaction effects were evident for any of these parameters.

Conclusion: The WI protocols investigated were not better than light exercise in facilitating recovery from shuttle running exercise. Future studies examining the efficacy of WI as a recovery intervention should include a representative control condition to increase their relevance to sporting populations.  相似文献   

14.
Abstract

In this study, we examined indirect markers of muscle damage and muscle soreness following a 50-km cross-country ski race completed in 2 h and 57 min to 5 h and 9 min by 11 moderately trained male university students. Maximal strength of the knee extensors, several blood markers of muscle damage and inflammation, and muscle soreness (visual analog scale: 0 = “no pain”, 50 mm = “unbearably painful”) were measured one day before, immediately after, and 24, 48, 72, and 144 h after the race. Changes in the measures over time were analysed using one-way repeated-measures analysis of variance and a Fisher's post-hoc test. Maximal strength of the knee extensors decreased significantly (P<0.05) immediately after the race (mean ?27%, s=6), but returned to pre-exercise values within 24 h of the race. All blood markers increased significantly (P<0.05) following the race, peaking either immediately (lactate dehydrogenase: 253.7 IU · l?1, s=13.3; myoglobin: 476.4 ng · ml?1, s=85.5) or 24 h after the race (creatine kinase: 848.0 IU · l?1, s=151.9; glumatic oxaloacetic transaminase: 44.3 IU · l?1, s=4.2; aldolase: 10.0 IU · l?1, s=1.3; C-reactive protein: 0.36 IU · l?1, s=0.08). Muscle soreness developed in the leg, arm, shoulder, back, and abdomen muscles immediately after the race (10–30 mm), but decreased after 24 h (<15 mm), and disappeared 48 h after the race. These results suggest that muscle damage induced by a 50-km cross-country ski race is mild and recovery from the race does not take long.  相似文献   

15.
This study aimed to assess the effects of core stability training on lower limbs’ muscular asymmetries and imbalances in team sport. Twenty footballers were divided into two groups, either core stability or control group. Before each daily practice, core stability group (n = 10) performed a core stability training programme, while control group (n = 10) did a standard warm-up. The effects of the core stability training programme were assessed by performing isokinetic tests and single-leg countermovement jumps. Significant improvement was found for knee extensors peak torque at 3.14 rad · s?1 (14%; P < 0.05), knee flexors peak torque at 1.05 and 3.14 rad · s?1 (19% and 22% with P < 0.01 and P < 0.01, respectively) and peak torque flexors/extensors ratios at 1.05 and 3.14 rad · s?1 (7.7% and 8.5% with P < 0.05 and P < 0.05, respectively) only in the core stability group. The jump tests showed a significant reduction in the strength asymmetries in core stability group (?71.4%; P = 0.02) while a concurrent increase was seen in the control group (33.3%; P < 0.05). This study provides practical evidence in combining core exercises for optimal lower limbs strength balance development in young soccer players.  相似文献   

16.
Joint moments can be used as an indicator of joint loading and have potential application for sports performance and injury prevention. The effects of changing walking and running speeds on joint moments for the different planes of motion still are debatable. Here, we compared knee and ankle moments during walking and running at different speeds. Data were collected from 11 recreational male runners to determine knee and ankle joint moments during different conditions. Conditions include walking at a comfortable speed (self-selected pacing), fast walking (fastest speed possible), slow running (speed corresponding to 30% slower than running) and running (at 4 m · s?1 ± 10%). A different joint moment pattern was observed between walking and running. We observed a general increase in joint load for sagittal and frontal planes as speed increased, while the effects of speed were not clear in the transverse plane moments. Although differences tend to be more pronounced when gait changed from walking to running, the peak moments, in general, increased when speed increased from comfortable walking to fast walking and from slow running to running mainly in the sagittal and frontal planes. Knee flexion moment was higher in walking than in running due to larger knee extension. Results suggest caution when recommending walking over running in an attempt to reduce knee joint loading. The different effects of speed increments during walking and running should be considered with regard to the prevention of injuries and for rehabilitation purposes.  相似文献   

17.
Although most ACL injury prevention programmes encourage greater hip and knee flexion during landing, it remains unknown how this technique influences tibiofemoral joint forces. We examined whether a landing strategy utilising greater hip and knee flexion decreases tibiofemoral anterior shear and compression. Twelve healthy women (25.9 ± 3.5 years) performed a drop-jump task before and after a training session (10–15 min) that emphasised greater hip and knee flexion. Peak tibiofemoral anterior shear and compressive forces were calculated using an electromyography (EMG)-driven knee model that incorporated joint kinematics, EMG and participant-specific muscle volumes and patella tendon orientation measured using magnetic resonance imaging (MRI). Participants demonstrated a decrease in peak anterior tibial shear forces (11.1 ± 3.3 vs. 9.6 ± 2.7 N · kg?1; P = 0.008) and peak tibiofemoral compressive forces (68.4 ± 7.6 vs. 62.0 ± 5.5 N · kg?1; P = 0.015) post-training. The decreased peak anterior tibial shear was accompanied by a decrease in the quadriceps anterior shear force, while the decreased peak compressive force was accompanied by decreased ground reaction force and hamstring forces. Our data provide justification for injury prevention programmes that encourage greater hip and knee flexion during landing to reduce tibiofemoral joint loading.  相似文献   

18.
Abstract

The aim of this study was to assess the effects of cold-water immersion (cryotherapy) on indices of muscle damage following a bout of prolonged intermittent exercise. Twenty males (mean age 22.3 years, s = 3.3; height 1.80 m, s = 0.05; body mass 83.7 kg, s = 11.9) completed a 90-min intermittent shuttle run previously shown to result in marked muscle damage and soreness. After exercise, participants were randomly assigned to either 10 min cold-water immersion (mean 10°C, s = 0.5) or a non-immersion control group. Ratings of perceived soreness, changes in muscular function and efflux of intracellular proteins were monitored before exercise, during treatment, and at regular intervals up to 7 days post-exercise. Exercise resulted in severe muscle soreness, temporary muscular dysfunction, and elevated serum markers of muscle damage, all peaking within 48 h after exercise. Cryotherapy administered immediately after exercise reduced muscle soreness at 1, 24, and 48 h (P < 0.05). Decrements in isometric maximal voluntary contraction of the knee flexors were reduced after cryotherapy treatment at 24 (mean 12%, s x  = 4) and 48 h (mean 3%, s x  = 3) compared with the control group (mean 21%, s x  = 5 and mean 14%, s x  = 5 respectively; P < 0.05). Exercise-induced increases in serum myoglobin concentration and creatine kinase activity peaked at 1 and 24 h, respectively (P < 0.05). Cryotherapy had no effect on the creatine kinase response, but reduced myoglobin 1 h after exercise (P < 0.05). The results suggest that cold-water immersion immediately after prolonged intermittent shuttle running reduces some indices of exercise-induced muscle damage.  相似文献   

19.
Abstract

In this study, we examined hamstring muscle activation at different running speeds to help better understand the functional characteristics of each hamstring muscle. Eight healthy male track and field athletes (20.1 ± 1.1 years) performed treadmill running at 50%, 75%, 85%, and 95% of their maximum velocity. Lower extremity kinematics of the hip and knee joint were calculated. The surface electromyographic activities of the biceps femoris and semitendinosus muscles were also recorded. Increasing the running speed from 85% to 95% significantly increased the activation of the hamstring muscles during the late swing phase, while lower extremity kinematics did not change significantly. During the middle swing phase, the activity of the semitendinosus muscle was significantly greater than that of the biceps femoris muscle at 75%, 85%, and 95% of running speed. Statistically significant differences in peak activation time were observed between the biceps femoris and semitendinosus during 95%max running (P < 0.05 for stance phase, P < 0.01 for late swing phase). Significant differences in the activation patterns between the biceps femoris and semitendinosus muscles were observed as running speed was increased, indicating that complex neuromuscular coordination patterns occurred during the running cycle at near maximum sprinting speeds.  相似文献   

20.
Upper-body dynamic and isometric maximum strength are essential components for success in Brazilian jiu-jitsu (BJJ). This study was aimed at analysing strength parameters in the elbow flexor and extensor muscles of BJJ practitioners. Participants (n = 28) performed maximum isometric contractions of elbow flexors and extensors to determine peak torque (PT), rate of force development (RFD), and the torque–angle (T–A) relationship at elbow angles of 45°, 60°, 75°, 90°, 105°, and 120°. Additionally, concentric and eccentric PTs were measured at 1.04 rad·s-1. Student t-test and ANOVA were performed using α = 0.05. Elbow flexors were stronger isometrically (P < 0.001, ES = 1.23) but weaker concentrically (P < 0.05, ES = 0.54) than extensor muscles, possibly because of the extensive grip disputes and pushing of opponents in BJJ. The T–A relationship had an inverted “U”-shape. Torque differences across elbow angles were moderate (ES = 0.62) for the extensor and large (ES = 0.92) for the flexor muscles. Isometric torque was greatest for elbow angles of 105° and 75° and smallest for 45° and 120° for extensor and flexor muscles, respectively. Elbow flexors had a greater RFD than extensors, regardless of elbow angle. The present study provides comprehensive results for elbow muscle strength in BJJ practitioners.  相似文献   

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