Influence of lower leg muscle fatigue on the centre of pressure in a static upright posture     

《European Journal of Sport Science》2013,13(3):135-141

Abstract

We examined the influence of fatigue in the lower leg muscles on the centre of pressure sway during a static upright posture. Twelve healthy young men and women completed the exercise stress test on the triceps surae muscle and continued the exercise until their muscles were fatigued. A centre of pressure sway of 1 min was carried out in a Romberg posture at rest and at different instants after fatiguing exercise: immediately after, 5 min after, and 10 min after exercise. Blood lactate concentration was measured from fingertip samples taken before and immediately after exercise. To evaluate body sway, the following four centre of pressure sway factors were selected: unit time sway, front–back sway, left–right sway, and high-frequency band power spectrum. The measurement device used was an Anima stabilometer (G5500). The data sampling frequency was 20 Hz. After exercise, blood lactate concentration was increased. Significant differences were observed in unit time sway, front–back sway, and high-frequency band power spectrum immediately after exercise. These values eventually returned to baseline levels 5 min after fatiguing exercise.  相似文献   

The influence of wearing compression stockings on performance indicators and physiological responses following a prolonged trail running exercise     

《European Journal of Sport Science》2013,13(2):144-150

Abstract

The objective of this study was to investigate the effects of wearing compression socks (CS) on performance indicators and physiological responses during prolonged trail running. Eleven trained runners completed a 15.6 km trail run at a competition intensity whilst wearing or not wearing CS. Counter movement jump, maximal voluntary contraction and the oxygenation profile of vastus lateralis muscle using near-infrared spectroscopy (NIRS) method were measured before and following exercise. Run time, heart rate (HR), blood lactate concentration and ratings of perceived exertion were evaluated during the CS and non-CS sessions. No significant difference in any dependent variables was observed during the run sessions. Run times were 5681.1±503.5 and 5696.7±530.7 s for the non-CS and CS conditions, respectively. The relative intensity during CS and non-CS runs corresponded to a range of 90.5–91.5% HR_max. Although NIRS measurements such as muscle oxygen uptake and muscle blood flow significantly increased following exercise (+57.7% and + 42.6%,+59.2% and + 32.4%, respectively for the CS and non-CS sessions, P<0.05), there was no difference between the run conditions. The findings suggest that competitive runners do not gain any practical or physiological benefits from wearing CS during prolonged off-road running.  相似文献   

Melatonin administration does not alter muscle glycogen concentration during recovery from exhaustive exercise in rats     

《European Journal of Sport Science》2013,13(2):174-182

Abstract

The purpose of this study was to investigate the effect of melatonin administration on muscle glycogen concentration during recovery after exhaustive swimming exercise in sedentary and trained rats. Male Wistar rats were assigned to one of four groups: sedentary control (C), sedentary melatonin-injected (M), exercise-trained (T), and trained and melatonin-injected (MT) groups. Exercise-trained groups were subjected to six weeks of swimming exercise. All rats completed an exhaustive swimming exercise. Two daily subcutaneous injections of melatonin at a dose of 3 mg·kg^?1 were given to the rats in the M and MT groups immediately after the exhaustive exercise. Plasma melatonin, glucose and lactate concentrations, and glycogen concentrations of the soleus and epitrochlearis muscle tissues were measured after exhaustive exercise. Plasma lactate concentration was significantly lower in the T and MT groups than in the C group. Plasma melatonin concentration was higher in the supplemented groups than in the C group. Plasma glucose concentration was significantly higher in the T and MT groups than in the C group. Both epitrochlearis and soleus muscle glycogen concentrations were higher in the trained groups than in the C group. In conclusion, although exercise training results in improvement in muscle glycogen, exogenous melatonin administration after exhaustive exercise did not restore the glycogen concentrations in fast- or slow-twitch muscle tissues.  相似文献   

Compressive properties of helmet materials subjected to dynamic impact loading of various energies     

《European Journal of Sport Science》2013,13(6):341-349

Abstract

Many helmet safety standards require children's helmets to be tested using adult-weighted headforms of approximately 5 kg and impact velocities representative of adult anatomy. The purpose of this study was to test the individual and combined effect of variable headform mass and inbound headform velocity on helmet test results. Testing was conducted on sample sections of helmet liner materials commonly used in multi- and single-impact helmets. Three densities of expanded polystyrene and expanded polypropylene were moulded into 2.54-cm thick foam blocks and cut into circular samples with a 5-cm diameter. Each sample was impacted once using an EN 960 magnesium K1A headform of variable mass on a monorail apparatus in the crown position. A total of 25 impact conditions were used: 5 headform masses and 5 inbound velocities. A PCB 203B force sensor collected force data at 20 kHz in the y-axis of the impact and a 1000-Hz low-pass Butterworth filter was applied during analysis. A three-way analysis of variance revealed significant main effects for headform mass, inbound velocity, and material density on peak linear acceleration (P<0.01). Inbound velocity and headform mass played a significant role in material performance. It is proposed that the headform mass and inbound velocity used in helmet testing protocols be representative of the intended age group to improve the performance range and safety of sport helmets.  相似文献   

Where are all the female participants in Sports and Exercise Medicine research?     

《European Journal of Sport Science》2013,13(8):847-851

Abstract

The aim of this study is to estimate the ratio of male and female participants in Sports and Exercise Medicine research. Original research articles published in three major Sports and Exercise Medicine journals (Medicine and Science in Sports and Exercise, British Journal of Sports Medicine and American Journal of Sports Medicine) over a three-year period were examined. Each article was screened to determine the following: total number of participants, the number of female participants and the number of male participants. The percentage of females and males per article in each of the journals was also calculated. Cross tabulations and Chi-square analysis were used to compare the gender representation of participants within each of the journals. Data were extracted from 1382 articles involving a total of 6,076,580 participants. A total of 2,366,968 (39%) participants were female and 3,709,612 (61%) were male. The average percentage of female participants per article across the journals ranged from 35% to 37%. Females were significantly under-represented across all of the journals (χ² = 23,566, df = 2, p < 0.00001). In conclusion, Sports and Exercise Medicine practitioners should be cognisant of sexual dimorphism and gender disparity in the current literature.  相似文献   

The influence of ankle dorsiflexion on jumping capacity and the modified agility t-test performance     

《European Journal of Sport Science》2013,13(2):137-143

Abstract

Dorsiflexion sport shoes aim to increase jumping capacity and speed by means of a lower position of the heel in comparison with the forefoot, favouring additional stretching of the ankle plantar flexors. In previous studies, contradictory results have been found on the benefits of using this type of shoe. With the aim of comparing a dorsiflexion sport shoe model (DF) with a conventional sport shoe (CS), 41 participants performed a countermovement jump (CMJ) test and an agility test (MAT) with both models of shoe. There were no significant differences in the jump test [CS=35.3 cm (6.4) and DF=35.6 cm (6.4), P>0.05]. In the agility test, the conventional shoe obtained better results than the model with dorsiflexion with regard to time taken to complete the circuit [CS=6236 ms (540) and DF=6377 ms (507), P<0.05)]. In spite of producing pre-stretching of the plantar muscles, the DF sport shoes were not effective for improving either jump power or agility in a specific test.  相似文献   

Comparison of the musculoskeletal effects of different iso-inertial resistance training modalities: Flywheel vs. electric-motor     

《European Journal of Sport Science》2013,13(9):1184-1194

Abstract

This study aimed to analyse whether increasing the eccentric overload (EO) during resistance training, in terms of range of motion and/or velocity using an electric-motor device, would induce different muscle adaptations than conventional flywheel-EO resistance training. Forty physically active university students (21.7?±?3.4 years) were randomly placed into one of the three training groups (EX1, EX2, FW) and a control group without training (n?=?10 per group). Participants in the training groups completed 12 sessions (4 sets of 7 repetitions) of iso-inertial single-leg squat training over 6 weeks for the dominant leg. Resistance was generated either by an electric-motor device at two different velocities for the eccentric phase; 100% (EX1) or 150% (EX2) of concentric speed, or by a conventional flywheel device (FW). Thigh lean tissue mass, unilateral leg press one-repetition maximum (1-RM), unilateral muscle power at different percentages of the 1-RM and bilateral/unilateral vertical jump were assessed before and after the 6-week training. There were significant (p?<?0.05–0.001) main effects of time in the 3 training groups, indicating increased thigh lean tissue mass (2.5–5.8%), 1-RM load (22.4–30.2%), vertical jump performance (9.1–32.9%) and muscle power (8.8–21.7%), without differences across experimental groups. Participants in the control group did not improve any of the variables measured. In addition, EX2 showed greater gains in eccentric average peak power during training than EX1 and FW (p?<?0.001). Despite the different EO offered, 6 weeks of resistance training using flywheel or electric-motor devices induced similar significant gains in muscle mass, strength, muscle power and vertical jump.  相似文献   

Effect of individualized resistance training prescription with heart rate variability on individual muscle hypertrophy and strength responses     

《European Journal of Sport Science》2013,13(8):1092-1100

Abstract

The aim of the present study was to investigate if resistance training (RT), performed with individualized recovery between sessions (RT-IND), promotes greater gains in strength and muscle mass and reduces the variability on adaptations compared to RT with fixed recovery intervals (RT-FIX). Twenty young men (age 21.9?±?3.3 years) were randomized in the RT-IND and RT-FIX groups. Five days before the beginning of the training, measurements of the root mean square of successive R-R intervals differences (RMSSD) values of each individual were performed to establish the baseline values. Before each RT session, the RMSSD values determined whether the participants from RT-IND protocol were recovered from the previous session. Participants performed the RT session only if RMSSD values had returned to the baseline, otherwise they had to wait for an additional 24?h. RT-FIX performed an RT session every 48?h. Muscle strength was measured by one-maximal repetition (1-RM) test and muscle cross-section area (CSA) of the vastus laterals by ultrasonography were assessed pre- and post-training. 1-RM values increased significantly from pre to post-training for both groups (RT-IND: 30% and RT-FIX: 42%, main time effect, P?<?0001), with no significant difference between groups. Muscle CSA increased significantly from pre to post-training (RT-IND: 15.7% and RT-FIX: 15.8%, main time effect, P?<?0001), with no significant difference between groups. In conclusion, RT-IND did not increase the gains in muscle strength and mass neither reduce the variability in muscle adaptations when compared to the RT-FIX.  相似文献   

Kinematic effects of repeated turns while running     

《European Journal of Sport Science》2013,13(8):1072-1081

Abstract

In team sports, non-contact ACL and MCL injuries occur during abrupt changes of direction, like turns or cutting manoeuvres. Fatigue affects dynamic neuromuscular control and increases knee injury risk. This study analysed how lower limb joints and centre-of-mass kinematics are affected throughout a high-intensity running protocol involving repeated 180°-turns. Twenty young men (18–23 years, BMI: 20.8–24.4?kg?m^?2) completed a 5-m shuttle running trial lasting 5?min at an average speed of 75% of their maximum aerobic speed. During the test, cardio-metabolic parameters were obtained, together with joints and centre-of-mass kinematics, using a motion capture system. Kinematic data were compared between the first and the last minute of exercise. Perceived exercise intensity ranged from “hard” to “maximum exertion” and post-exercise lactate concentration ranged from 5.4 to 15.5?mM. The repetition of 180°-turns induced a substantial reduction of hip (?60%, p?<?.001, large effect) and knee flexion (?40%, p?=?.003, medium-to-large effect), and an increase of hip adduction and internal rotation (+25–30%, p?<?.05, medium-to-large effect). Since such movements are factors increasing the likelihood of non-contact knee injuries, we concluded that the prolonged repetition of turns may expose participants to increased risk of ligament failure. Prevention programmes should include discipline-specific neuromuscular training especially in late practices.  相似文献   

运动对骨骼肌线粒体生物合成调节因子影响进展研究     

王震 《吉林体育学院学报》2013,(4):93-97

运动激活细胞信号诱导线粒体生物合成,不仅可以有效地增加线粒体体积、提高ATP供能能力和延缓运动性疲劳发生,还可预防与年龄相关的退行性改变而导致肌肉功能下降。随年龄增长且运动时间减少,线粒体通道受损导致有氧功能减退和细胞凋亡趋势增加可导致肌肉功能下降。通过选择合适的运动方式,能改善这种代谢功能障碍,维持肌肉质量。  相似文献