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1.
Abstract

Previous studies have shown that cycling can directly influence neuromuscular control during subsequent running in some highly trained triathletes, despite these triathletes' years of practice of the cycle–run transition. The aim of this study was to determine whether cycling has the same direct influence on neuromuscular control during running in moderately trained triathletes. Fifteen moderately trained triathletes participated. Kinematics of the pelvis and lower limbs and recruitment of 11 leg and thigh muscles were compared between a control run (no prior exercise) and a 30 min run that was preceded by a 15 min cycle (transition run). Muscle recruitment was different between control and transition runs in only one of 15 triathletes (<7%). Changes in joint position (mean difference of 3°) were evident in five triathletes, which persisted beyond 5 min of running in one triathlete. Our findings suggest that some moderately trained triathletes have difficulty reproducing their pre-cycling movement patterns for running initially after cycling, but cycling appears to have little influence on running muscle recruitment in moderately trained triathletes.  相似文献   

2.
Previous studies have shown that cycling can directly influence neuromuscular control during subsequent running in some highly trained triathletes, despite these triathletes' years of practice of the cycle-run transition. The aim of this study was to determine whether cycling has the same direct influence on neuromuscular control during running in moderately trained triathletes. Fifteen moderately trained triathletes participated. Kinematics of the pelvis and lower limbs and recruitment of 11 leg and thigh muscles were compared between a control run (no prior exercise) and a 30 min run that was preceded by a 15 min cycle (transition run). Muscle recruitment was different between control and transition runs in only one of 15 triathletes (<7%). Changes in joint position (mean difference of 3°) were evident in five triathletes, which persisted beyond 5 min of running in one triathlete. Our findings suggest that some moderately trained triathletes have difficulty reproducing their pre-cycling movement patterns for running initially after cycling, but cycling appears to have little influence on running muscle recruitment in moderately trained triathletes.  相似文献   

3.
The study examined the differences between boys and adults after an intense stretch-shortening cycle fatigue protocol on neuromechanical parameters of the lower limb. Thirteen boys (9–11 years old) and 13 adult men (22–28 years old) were tested for maximal isometric voluntary knee extension torque and drop jump (DJ) performance from 30 cm before and immediately after a fatigue protocol, consisted of 10 × 10 maximum effort vertical jumps. Three-dimensional kinematics, kinetics and electromyographic (EMG) parameters of the lower extremities muscles were recorded during DJs before and after the fatigue test. The results indicated that reduction in maximal isometric torque and jumping performance was significantly higher in adults compared to boys. Vertical ground reaction forces, contact time and maximum knee flexion increased in a greater extend in adults than in boys. In addition, preactivation, EMG agonist activity, knee joint stiffness and stretch reflex decreased more in adults than in boys at all the examined phases of jumping tasks. It is concluded that employed fatigue protocol induced acute reduction in performance and altered motor control during jumping in both age groups. However, the differences in the level of fatigue between the 2 groups could be attributed to neuromuscular, mechanical and kinematic parameters observed between groups.  相似文献   

4.
In habitually shod recreational runners, we studied the combined influence of footwear and stretch-shortening cycle (SSC) fatigue on treadmill running pattern, paying special attention to neuro-mechanical adjustments in the acute and 2-day delayed recovery periods. The SSC exercise consisted of a series of 25 sub-maximal rebounds on a sledge apparatus repeated until exhaustion. The acute and delayed functional fatigue effects were quantified in a maximal drop jump test. The neuro-mechanical adjustments to fatigue were examined during two submaximal treadmill run tests of 3 min performed either barefoot or with shoes on. Surface electromyographic (EMG) activities, tibial accelerations and kinematics of the right lower limb were recorded during the first and last 15 s of each run. The main result was that neuro-mechanical differences between the shod and barefoot running patterns, classically reported in the absence of fatigue, persisted in the fatigued state. However, in the delayed recovery phase, rearfoot eversion was found to significantly increase in the shod condition. This specific footwear effect is considered as a potential risk factor of overuse injuries in longer runs. Therefore, specific care should be addressed in the delayed recovery phase of SSC fatigue and the use of motion control shoes could be of interest.  相似文献   

5.
We investigated the association between changes in vastii electromyography (EMG) and knee extensor fatigue during high-intensity cycling, and the subsequent effect on lower-limb power and intermuscular coordination during all-out cycling. On two separate days, participants completed 30-s all-out cycling or 10-min of high-intensity cycling followed by 30-s all-out cycling. EMG for gluteus maximus (GMAX), rectus femoris (RF), vastii (VAS), hamstrings (HAM) and gastrocnemius (GAS); co-activation for GMAX/RF, VAS/HAM and VAS/GAS; isometric maximal voluntary force (IMVF) and resting twitch (RT) of the knee extensors were measured. VAS EMG increases during high-intensity cycling (6% to 14%, P < 0.05) were negatively correlated (r = ?0.791, P < 0.05) with knee extensor IMVF decreases (?2% to?36%, P < 0.05) following the exercise. Knee extensor IMVF decreases were positively correlated (r = 0.757, P < 0.05) with all-out cycling power reductions (0% to ?27%, P < 0.05). VAS/GAS co-activation did not change (P > 0.05) during all-out cycling while VAS and GAS EMG decreased. Larger increase in VAS EMG during high-intensity cycling was associated with greater knee extensor fatigue and larger power reduction during all-out cycling. High VAS/GAS co-activation potentially limited power reduction induced by knee extensor fatigue during all-out cycling.  相似文献   

6.
Abstract

This study investigated the effects of knee localised muscle damage on running kinematics at varying speeds. Nineteen young women (23.2 ± 2.8 years; 164 ± 8 cm; 53.6 ± 5.4 kg), performed a maximal eccentric muscle damage protocol (5 × 15) of the knee extensors and flexors of both legs at 60 rad · s-1. Lower body kinematics was assessed during level running on a treadmill at three speeds pre- and 48 h after. Evaluated muscle damage indices included isometric torque, muscle soreness and serum creatine kinase activity. The results revealed that all indices changed significantly after exercise, indicating muscle injury. Step length decreased and stride frequency significantly increased 48 h post-exercise only at the fastest running speed (3 m · s-1). Support time and knee flexion at toe-off increased only at the preferred transition speed and 2.5 m · s-1. Knee flexion at foot contact, pelvic tilt and obliquity significantly increased, whereas hip extension during stance-phase, knee flexion during swing-phase, as well as knee and ankle joints range of motion significantly decreased 48 h post-exercise at all speeds. In conclusion, the effects of eccentric exercise of both knee extensors and flexors on particular tempo-spatial parameters and knee kinematics of running are speed-dependent. However, several pelvic and lower joint kinematics present similar behaviour at the three running speeds examined. These findings provide new insights into how running kinematics at different speeds are adapted to compensate for the impaired function of the knee musculature following muscle damage.  相似文献   

7.
The main purpose of this study was to evaluate running kinematic characteristics and foot strike patterns (FSP) during early and late stages of actual and common high-intensity intermittent training (HIIT): 5 × 2000 m with 120-s recovery between runs. Thirteen healthy, elite, highly trained male endurance runners participated in this study. They each had a personal record in the half-marathon of 70 ± 2.24 min, and each had a minimum experience of 4 years of training and competition. Heart rate (HR) and rate of perceived exertion (RPE) were monitored during HIIT. High levels of exhaustion were reached by the athletes during HIIT (HRpeak: 174.30 bpm; RPE: 17.23). There was a significant increase of HRpeak and RPE during HIIT; nevertheless, time for each run remained unchanged. A within-protocol paired t-test (first vs. last run) revealed no significant changes (P ≥ 0.05) in kinematics variables and FSP variables during HIIT. There were no substantial changes on kinematics and FSP characteristics in endurance runners after fatigue induced by a HIIT. Only the minimum ankle alignment showed a significant change. The author suggests that these results might be due to both the high athletic level of participants and their experience in HIIT.  相似文献   

8.
In this study, we examined whether self-selected overground running speed was consistent (1) with perceived overground speed on the treadmill and (2) among barefoot and three footwear conditions. Participants ran across a 20-m runway 10 times for each overground condition, with running speed calculated from kinematic data. For the treadmill condition, the participants were instructed to run at a speed that felt similar to their overground speed. This treadmill speed was chosen upon perception, with the display covered from the participant's view. Repeated-measures analysis of variance was used to detect differences in speed between overground and treadmill running, and also among barefoot and footwear conditions. Coefficient alpha (α) was calculated to determine repeatability of observations in each overground condition. The speed was higher during overground (3.65 ± 0.40 m/s) than treadmill (2.25 ± 0.75 m/s) running but did not differ among the barefoot and the three footwear conditions. Overall, overground speed was highly repeatable within an individual (α = 0.96–0.98). Researchers might consider using self-selected speed when investigating overground running mechanics with different foot–ground interface conditions. The influence of treadmill on the perception of speed may be related to shear force, running duration, joint load control, and/or other psychological factors.  相似文献   

9.
The aim of this study was to observe changes in the kinematics and muscle activities when barefoot running was initially adopted by six habitually shod, recreational rearfoot striking runners. Participants ran on a treadmill shod for 5 min, completed 3 × 10-min intervals of barefoot running and then completed a final minute of shod running at a self-selected pace. Dependent variables (speed, joint angles at foot-contact, joint range of motion (ROM), mean and peak electromyography (EMG) activity) were compared across conditions using repeated measures ANOVAs. Anterior pelvic tilt and hip flexion significantly decreased during barefoot conditions at foot contact. The ROM for the trunk, pelvis, knee and ankle angles decreased during the barefoot conditions. Mean EMG activity was reduced for biceps femoris, gastrocnemius lateralis and tibialis anterior during barefoot running. The peak activity across the running cycle decreased in biceps femoris, vastus medialis, gastrocnemius medialis and tibialis anterior during barefoot running. During barefoot running, tibialis anterior activity significantly decreased during the pre-activation and initial contact phases; gastrocnemius lateralis and medialis activity significantly decreased during the push-off phase. Barefoot running caused immediate biomechanical and neuromuscular adaptations at the hip and pelvis, which persisted when the runners donned their shoes, indicating that some learning had occurred during an initial short bout of barefoot running.  相似文献   

10.
Abstract

This study assessed muscle recruitment patterns and stroke kinematics during ergometer and on-water rowing to validate the accuracy of rowing ergometry. Male rowers (n = 10; age 21 ± 2 years, height 1.90 ± 0.05 m and body mass 83.3 ± 4.8 kg) performed 3 × 3 min exercise bouts, at heart and stroke rates equivalent to 75, 85 and 95% V?O2peak, on both dynamic and stationary rowing ergometers, and on water. During exercise, synchronised data for surface electromyography (EMG) and 2D kinematics were recorded. Overall muscle activity was quantified by the integration of rmsEMG and averaged for each 10% interval of the stroke cycle. Muscle activity significantly increased in rectus femoris (RF) and vastus medialis (VM) (P <0.01), as exercise intensity increased. Comparing EMG data across conditions revealed significantly (P <0.05) greater RF and VM activity during on-water rowing at discrete 10% intervals of stroke cycle. In addition, the drive/recovery ratio was significantly lower during dynamic ergometry compared to on-water (40 ± 1 vs. 44 ± 1% at 95%, P <0.01). Results suggest that significant differences exist while comparing recruitment and kinematic patterns between on-water and ergometer rowing. These differences may be due to altered acceleration and deceleration of moving masses on-ergometer not perfectly simulating the on-water scenario.  相似文献   

11.
Team handball is a popular sport worldwide that requires numerous throws to be made throughout the course of a game. Because of the upper extremity demands of repetitive throwing, it is possible that fatigue can alter the mechanics of a shot. The purpose of this study was to determine the influence of localised fatigue on jump shot kinematics and kinetics. Eleven male team handball players (23.1 ± 3.1 years; 185.1 ± 8.3 cm; 89.7 ± 12.2 kg) volunteered. An electromagnetic tracking system was used to examine the jump shot prior to and following localised fatigue. The fatiguing protocol consisted of throwing a 2.2 kg medicine ball into a rebounder until volitional fatigue. No significant kinematic or kinetic differences were observed following fatigue. Shoulder external rotation was ?74.8 ± 14.9° prior to and ?79.0 ± 14.7° following fatigue at MER. Scapula, external rotation at ball release (BR) prior to fatigue was ?2.2 ± 7.0° and ?3.2 ± 11.1° following fatigue. Scapular internal rotation, at maximum shoulder internal rotation (MIR), changed from 18.4 ± 11.2° to 20.4 ± 11.8°. Ball velocity decreased from19.8 m · s–1 to 18.8 m · s–1 (P = 0.12). Accuracy percentage in the pre-fatigue trials was 60.8 ± 14.1% and 52.8 ± 12.7% following fatigue (P = 0.20). While no significant changes were observed, it is possible that other fatiguing protocols that more closely represent the aerobic and throwing demands of the sport may have a greater effect on the kinematics and kinetics of the jump shot.  相似文献   

12.
The present study aimed to investigate the effects of a standardized fatiguing protocol on central and peripheral fatigue in knee-flexors and knee-extensors. Thirteen healthy men (age: 23?±?3 years; height: 1.78?±?0.09 m; body-mass: 73.6?±?9.2?kg) volunteered for the present study. Maximal voluntary contraction (MVC), Electromyography (EMG) activity, voluntary activation level (VAL) as an index of central fatigue and twitch potentiation as an index of peripheral fatigue were measured before and after the fatiguing protocol. The fatiguing protocol consisted of a 0.6 duty-cycle to exhaustion (6?s isometric contraction, 4?s recovery) at 70% MVC. After the fatiguing protocol, MVC decreased in both (Effect-size (ES)?=?1.14) and knee-extensors (ES?=?1.14), and EMG activity increased in both knee-flexors (ES?=?2.33) and knee-extensors (ES?=?1.54). Decreases in VAL occurred in knee-flexors (ES?=?0.92) but not in knee-extensors (ES?=?0.04). Decreases in potentiation occurred in both knee-flexors (ES?=?0.84) and knee-extensors (ES?=?0.58). The greater central occurrence of fatigue in knee-flexors than in knee-extensors may depend on the different muscle morphology and coupled with a greater tolerance to fatigue in knee-extensors. The present data add further insight to the complicated knee-flexors-to-knee-extensors strength relationship and the mechanisms behind the different occurrence of fatigue.  相似文献   

13.
It is common for the physiological working capacity of a triathlete when cycling and running to be assessed on two separate days. The aim of this study was to establish whether an incremental running test to exhaustion has a negative effect after a 5 h recovery from an incremental cycling test. Eight moderately trained triathletes (age, 26.2 +/- 3.4 years; body mass, 67.3 +/- 9.1 kg; VO2max when cycling, 59 +/- 13 ml x kg x min(-1); mean +/- s) completed an incremental running test 5 h after an incremental cycling test (fatigue) as well as an incremental running test without previous activity (control). Maximum running speed, maximal oxygen uptake (VO2max) and the lactate threshold were determined for each incremental running test and correlated with the average speed during a 5 km run, which was performed immediately after a 20 km cycling time-trial, as in a sprint triathlon. There were no significant differences in maximum running speed, VO2max or the lactate threshold in either incremental running test (control or fatigue). Furthermore, good agreement was found for each physiological variable in both the control and fatigue tests. For the fatigue test, there were significant correlations between the average speed during a 5 km run and both VO2max expressed in absolute terms (r = 0.83) and the lactate threshold (r = 0.88). However, maximum running speed correlated most strongly with the average speed during a 5 km run (r = 0.96). The results of this study indicate that, under controlled conditions, an incremental running test can be performed successfully 5 h after an incremental cycling test to exhaustion. Also, the maximum running speed achieved during an incremental running test is the variable that correlates most strongly with the average running speed during a 5 km run after a 20 km cycling time-trial in well-trained triathletes.  相似文献   

14.
Fatigue protocols have been used over the years to examine muscular exhaustion. As an alternative to approaches in laboratory settings, functional agility protocols claiming to mimic the multifaceted loads of athletic activity have been proposed. This study aimed to examine the effects of a functional agility short-term fatigue protocol (FAST-FP) on neuromuscular function. Twenty-eight healthy sports students (15 males, aged 24.3 ± 2.4 years) completed the FAST-FP, which consists of four components: three counter-movement jumps (90% of individual maximum), a 20-s bout of step-ups, three bodyweight squats and an agility run. Tasks were repeated until the participants no longer achieved the required jump height in two consecutive sets. Outcomes (pre-post) encompassed subjective exhaustion (visual analogue scale [VAS]), maximum isometric voluntary force of the knee extensors (MIVF), reactive strength index (RSI), mean power frequency (MPF, measured using surface electromyography) and maximum knee range of motion (ROM). Post-intervention, VAS (+54 mm) increased significantly, while MIVF (–6.1%), RSI (–10.7%) and MPF (–4.1%) were reduced (p < 0.05). No changes were observed for ROM (p > 0.05). The FAST-FP induces small-to-moderate impairments in neuromuscular function and considerable self-perceived fatigue. Current evidence on exhaustion developing in team sports suggests that this magnitude of fatigue is similar. The protocol might thus be valuable in the evaluation of treatments counteracting post-match fatigue in team sports.  相似文献   

15.
Abstract

Research with cyclists suggests a decreased load on the lower limbs by placing the shoe cleat more posteriorly, which may benefit subsequent running in a triathlon. This study investigated the effect of shoe cleat position during cycling on subsequent running. Following bike-run training sessions with both aft and traditional cleat positions, 13 well-trained triathletes completed a 30?min simulated draft-legal triathlon cycling leg, followed by a maximal 5?km run on two occasions, once with aft-placed and once with traditionally placed cleats. Oxygen consumption, breath frequency, heart rate, cadence and power output were measured during cycling, while heart rate, contact time, 200?m lap time and total time were measured during running. Cardiovascular measures did not differ between aft and traditional cleat placement during the cycling protocol. The 5?km run time was similar for aft and traditional cleat placement, at 1084?±?80?s and 1072?±?64?s, respectively, as was contact time during km 1 and 5, and heart rate and running speed for km 5 for the two cleat positions. Running speed during km 1 was 2.1%?±?1.8 faster (P?<?0.05) for the traditional cleat placement. There are no beneficial effects of an aft cleat position on subsequent running in a short distance triathlon.  相似文献   

16.
Fatigue, developed over the course of a run, may cause changes in running kinematics. Training status may influence the effect of fatigue on running kinematics, since well trained, competitive runners are used to running until exhaustion, whereas novice runners are not. This study aimed to determine changes in running kinematics during an exhaustive run in both novice (NOVICE) and competitive (COMP) long-distance runners. About 15 NOVICE and 15 COMP runners performed a treadmill run, until voluntary exhaustion at 3,200 m time trial pace. Joint angles and global trunk and pelvis angles were recorded at the beginning and at the end of the run. In both groups, peak pelvic anterior tilt, pelvic rotation range of motion (both during stance phase) and ankle plantar flexion during swing phase increased after the exhaustive run. There was a significant interaction effect between group and exhaustion for peak forward trunk lean, which increased only in the NOVICE group, and for hip abduction during mid-swing, which increased in NOVICE and decreased in COMP runners. In conclusion, NOVICE runners showed larger kinematic adjustments when exhausted than COMP runners. This may affect their running performance and should be taken into account when assessing a runner’s injury risk.  相似文献   

17.
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   

18.
The aim of this study was to investigate how the type of contact influences physiological, perceptual and locomotive load during a simulated rugby league match. Eleven male university rugby league players performed two trials of the rugby league movement simulation protocol for interchange forwards with a traditional soft tackle bag and a weighted tackle sled to replicate contact demands. The interchange forward-specific simulation was chosen given the contact frequency is higher for this group of players compared to whole match players. Locomotive rate, sprint speed, tackle intensity, heart rate (HR) and rating of perceived exertion were analysed during the first and second bouts that replicated two ~23 min on-field passages. Countermovement jump (CMJ) was measured before and immediately after each trial. More time was spent in heart rate zone between 91 and 100% HRpeak during the first (effect size ± 90% confidence interval: 0.44 ± 0.49) and second bouts (0.44 ± 0.43), and larger (0.6 ± 0.69) decrements in CMJ performance were observed during the sled trial (5.9, s = 4.9%) compared to the bag trial (2.6, s = 5.4%). Changing the type of contact during the match simulation subtly altered both the internal and external loads on participants. Using a standard tackle bag results in faster sprint speed to contact, but lower overall high-intensity running. Conversely, a heavier tackle object increases the internal load and results in greater lower limb neuromuscular fatigue as reflected by the decrease in CMJ performance.  相似文献   

19.
Abstract

The aim of the study was to examine the sticking region and concomitant neuromuscular activation of the prime movers during six-repetition maximum (RM) bench pressing. We hypothesised that both peak velocities would decrease and that the electromyography (EMG) of the prime movers (deltoid, major pectoralis and triceps) would increase during the pre-sticking and sticking region during the six repetitions due to fatigue. Thirteen resistance-trained males (age 22.8 ± 2.2 years, stature 1.82 ± 0.06 m, body mass 83.4 ± 7.6 kg) performed 6-RM bench presses. Barbell kinematics and EMG activity of pectoralis major, deltoid anterior, and triceps brachii during the pre-, sticking and post-sticking region of each repetition in a 6-RM bench press were analysed. For both the sticking as the post-sticking region, the time increased significantly from the first to the sixth repetition. Vertical barbell height at the start of sticking region was lower, while the height at the end of the sticking region and post-sticking region did not change during the six repetitions. It was concluded that in 6-RM bench pressing performance, the sticking region is a poor mechanical force region due to the unchanged barbell height at the end of the sticking region. Furthermore, when fatigue occurs, the pectoralis and the deltoid muscles are responsible for surpassing the sticking region as indicated by their increased activity during the pre- and sticking region during the six-repetitions bench press.  相似文献   

20.
Running is the most important discipline for Olympic triathlon success. However, cycling impairs running muscle recruitment and performance in some highly trained triathletes; though it is not known if this occurs in elite international triathletes. The purpose of this study was to investigate the effect of cycling in two different protocols on running economy and neuromuscular control in elite international triathletes. Muscle recruitment and sagittal plane joint angles of the left lower extremity and running economy were compared between control (no preceding cycle) and transition (preceded by cycling) runs for two different cycle protocols (20-minute low-intensity and 50-minute high-intensity cycles) in seven elite international triathletes. Muscle recruitment and joint angles were not different between control and transition runs for either cycle protocols. Running economy was also not different between control and transition runs for the low-intensity (62.4 +/- 4.5 vs. 62.1 +/- 4.0 ml/min/kg, p > 0.05) and high-intensity (63.4 +/- 3.5 vs. 63.3 +/- 4.3 ml/min/kg, p > 0.05) cycle protocols. The results of this study demonstrate that both low- and high-intensity cycles do not adversely influence neuromuscular control and running economy in elite international triathletes.  相似文献   

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