The effects of maximal and submaximal arm crank ergometry and cycle ergometry on postural sway

Abstract

This study aimed to determine whether arm crank ergometry (ACE) disturbed postural sway to the same extent as cycle ergometry (CE). Nine healthy, none specifically trained adults undertook posturographic tests before and after five separate exercise trials consisting of: two incremental exercise tests to exhaustion for ACE and CE to examine postural sway responses to maximal exercise and to determine peak power output (W_max); two subsequent tests of 30 min duration for ACE and CE at a relative workload corresponding to 50% of the ergometer-specific W_max (ACE_rel; 53 ± 8 W and CE_rel; 109 ± 16 W). A final CE trial was performed at the same absolute power output (CE_abs) as the submaximal ACE trial to match absolute exercise intensity (i.e., 53 ± 8 W). The centre of pressure (COP) displacement was recorded using a force platform before, immediately after exercise and during a 30-min recovery period. ACE had no effects on postural sway (P > 0.05). An increase in mediolateral COP displacement was observed following maximal CE only (P = 0.001), while anteroposterior COP displacement and COP path length increased following maximal and submaximal CE (P < 0.05). These differences in postural sway according to exercise mode likely stem from the activity of postural muscles when considering that CE recruits lower limb muscles involved in balance. This study provides evidence of an exercise mode which does not elicit post-exercise balance impairments, therefore possesses applications to those at an increased risk of falling.     

Effect of bag holding on the center of foot pressure and the lower leg muscle activities

Abstract

This study examined the influence of holding a bag with one hand on the center of foot pressure (COP) and the electromyographic responses in lower leg muscles. Thirteen healthy male adults participated in this study to keep an upright posture while holding a load with the dominant hand with four bag weight conditions (0%, 15%, 30%, and 45% of maximal voluntary contraction (MVC) of the jerk strength). Integrated Electromyography (iEMG) and mean power frequency (MPF) of EMG were calculated to estimate the degree of muscle activity and fatigue in the tibialis anterior and soleus that are involved in ankle joint control. Body sway was evaluated by the mean position of left-right (X) and front-back (Y) axis sway and the following 4 body sway factors; unit time sway factor (F1), front-back sway factor (F2), left-right sway factor (F3), high frequency band power spectrum factor (F4). When holding a bag at 45% MVC or more of the jerk strength with a single hand for one minute, muscle activity in the lower leg on the side of the bag increased markedly, and muscle fatigue was induced in the antigravity muscles of both legs. As a result, anteroposterior sway increased to a short, quick sway.     

Centre of pressure sway characteristics during static one-legged stance of athletes from different sports

Abstract

The frequency of one-legged stance and two-legged stance differs considerably among sports. We therefore expect the balance ability of athletes from different sports to vary. This study compared the sway characteristics during a static one-legged stance of soccer players, basketball players, swimmers, and non-athletes. The centre of pressure sway during one-legged stance of ten male participants representing each of the four groups was measured using a stabilometer. Centre of pressure sway was assessed by four sway factors: sway velocity, anterior-posterior sway, horizontal sway, and high-frequency sway. None of the four groups of participants showed significant differences in body sway between standing on the dominant leg and standing on the non-dominant leg. The soccer players had more high-frequency sway and less anterior-posterior sway and horizontal sway than the basketball players, swimmers, and non-athletes. These results suggest that soccer players have superior ability to maintain a stable one-legged stance. Further study is required to determine how much of the superior balance ability in soccer players is innate and how much is developed through training, as well as to determine the relationship between balance ability and playing performance.     

Stretching and deep and superficial massage do not influence blood lactate levels after heavy-intensity cycle exercise

Abstract

The study aimed to assess the role of deep and superficial massage and passive stretching recovery on blood lactate concentration ([La^?]) kinetics after a fatiguing exercise compared to active and passive recovery. Nine participants (age 23 ± 1 years; stature 1.76 ± 0.02 m; body mass 74 ± 4 kg) performed on five occasions an 8-min fatiguing exercise at 90% of maximum oxygen uptake, followed by five different 10-min interventions in random order: passive and active recovery, deep and superficial massage and stretching. Interventions were followed by 1 hour of recovery. Throughout each session, maximum voluntary contraction (MVC) of the knee extensor muscles, [La^?], cardiorespiratory and metabolic variables were determined. Electromyographic signal (EMG) from the quadriceps muscles was also recorded. At the end of the fatiguing exercise, [La^?], MVC, EMG amplitude, and metabolic and cardiorespiratory parameters were similar among conditions. During intervention administration, [La^?] was lower and metabolic and cardiorespiratory parameters were higher in active recovery compared to the other modalities (P < 0.05). Stretching and deep and superficial massage did not alter [La^?] kinetics compared to passive recovery. These findings indicate that the pressure exerted during massage administration and stretching manoeuvres did not play a significant role on post-exercise blood La^? levels.     

Knee extension fatigue attenuates repeated force production of the elbow flexors

Abstract

Non-local muscle fatigue has been demonstrated with unilateral activities, where fatiguing one limb alters opposite limb forces. Fewer studies have examined if non-local fatigue occurs with unrelated muscles. The purpose of this study was to investigate if knee extensors fatigue alters elbow flexors force and electromyography (EMG) activity. Eighteen males completed a control and fatiguing session (randomised). Blood lactate was initially sampled followed by three maximal voluntary contractions (MVC) with the elbow flexors and two with the knee extensors. Thereafter, subjects either sat (control) or performed five sets of bilateral dynamic knee extensions to exhaustion using a load equal to the dominant limb MVC (1-min rest between sets). Immediately afterwards, subjects were assessed for blood lactate and unilateral knee extensors MVC, and after 1 min performed a single unilateral elbow flexor MVC. Two minutes later, subjects performed 12 unilateral elbow flexor MVCs (5 s contraction/10 s rest) followed by a third blood lactate test. Compared to control, knee extensor force dropped by 35% (p < 0.001; ES = 1.6) and blood lactate increased by 18% (p < 0.001; ES = 2.8). Elbow flexor forces were lower after the fatiguing protocol only during the last five MVCs (p < 0.05; ES = ～0.58; ～5%). No changes occurred between conditions in EMG. Elbow flexor forces significantly decreased after knee extensors fatigue. The effect was revealed during the later stages of the repeated MVCs protocol, demonstrating that non-local fatigue may have a stronger effect on repeated rather than on single attempts of maximal force production.     

Effects of Different Intensities of Exercise on Intraocular Pressure

Abstract

Males (N = 7), ages 23–45, were tested on a maximum and two submaximum performance tests to determine the effects of different intensities of exercise on intraocular pressure. Intraocular pressure, blood pH, and blood lactate concentration were measured at rest, the midpoint of the submaximum tests, the end of exercise, and during the first 10 min of recovery. A two-way ANOVA was employed to determine if any significant differences existed between means due to the exercise or the intensity. The results of this study indicate that the intraocular pressure decreases during exercise and the first few minutes of recovery. However, the intensity of the exercise was not related to the amount of decrease in intraocular pressure. The decrease in pressure was associated with a decrease in blood pH and an increase in blood lactate concentration.     

不同压力下肢紧身服对跑步运动中摄氧量及运动后血乳酸恢复的影响

研究目的:研究穿着不同压力下肢紧身服对跑步过程中摄氧量以及运动后血乳酸恢复的影响。研究方法:选择北京体育大学12名健康男性长跑爱好者作为研究对象。受试者进行3次递增负荷最大摄氧量测试,在测试期间随机穿戴不同压力的下肢紧身服和普通运动长裤进行测试。最大摄氧量测试采用METAMAX 3B心肺功能测试系统进行测试,根据Bruce测试方案每3 min递增负荷,直至受试者运动至力竭。分别在安静时、运动后1 min、4 min、7 min和10 min 5个时刻测量血乳酸指标。采用Simi Aktisys 3D实验设备进行肌肉震动测试。采用一般线性模型的重复测量统计学方法比较3种情况下各项指标的差异。研究结果:运动过程中,高压力下肢紧身服在第二负荷上的耗氧量显著减小(P=0.047),但在其他负荷的耗氧量以及最大摄氧量没有出现显著性的差异。不同压力下肢紧身服对乳酸最大值以及乳酸消除速率没有产生显著性的影响。不同压力下肢紧身服均能够显著减小股四头肌、股二头肌和腓肠肌的肌肉震动(P=0.017、P=0.012、P=0.028),并且压力较大的下肢紧身服对肌肉的固定效果更好。研究结论:不同压力下肢紧身服对一次性高强度跑步运动过程中的最大摄氧量没有显著性的影响,但有可能在一定运动强度范围内减少运动过程中氧气的消耗。下肢紧身服对一次性高强度跑步运动后乳酸恢复没有显著性的影响。下肢紧身服能够降低肌肉的额外震动,并且压力越大,效果越好。     

Changes in transverse relaxation time of quadriceps femoris muscles after active recovery exercises with different intensities

Abstract

The purpose of this study was to examine the changes in the metabolic state of quadriceps femoris muscles using transverse relaxation time (T2), measured by muscle functional magnetic resonance (MR) imaging, after inactive or active recovery exercises with different intensities following high-intensity knee-extension exercise. Eight healthy men performed recovery sessions with four different conditions for 20 min after high-intensity knee-extension exercise on separate days. During the recovery session, the participants conducted a light cycle exercise for 20 min using a cycle (50%, 70% and 100% of the lactate threshold (LT), respectively: active recovery), and inactive recovery. The MR images of quadriceps femoris muscles were taken before the trial and after the recovery session every 30 min for 120 min. The percentage changes in T2 for the rectus femoris and vastus medialis muscles after the recovery session in 50%LT and 70%LT were significantly lower than those in either inactive recovery or 100%LT. There were no significant differences in those for vastus lateralis and vastus intermedius muscles among the four trials. The percentage changes in T2 of rectus femoris and vastus medialis muscles after the recovery session in 50%LT and 70%LT decreased to the values before the trial faster than those in either inactive recovery or 100%LT. Those of vastus lateralis and vastus intermedius muscles after the recovery session in 50%LT and 70%LT decreased to the values before the trial faster than those in 100%LT. Although the changes in T2 after active recovery exercises were not uniform in exercised muscles, the results of this study suggest that active recovery exercise with the intensities below LT are more effective to recover the metabolic state of quadriceps femoris muscles after intense exercise than with either intensity at LT or inactive recovery.     

短时间力竭运动血清生长激素水平与血糖和血乳酸浓度相关性研究

测定了男性大学生短时间力竭运动前后不同时刻血清GH、BG和LA的浓度。结果显示:短时间力竭运动后即刻BG浓度显著高于运动前安静值(P<0 01);运动后30min、运动后60min时BG浓度与安静值无显著性差异,运动后BG浓度呈恢复趋势;运动后即刻、运动后30min时血液LA水平显著高于运动前安静值(P<0 01),运动后60min时LA水平高于运动前安静值(P<0 05),呈恢复趋势;短时间力竭运动后血液LA浓度的变化与GH浓度的变化呈显著正相关(r=0 83,P<0 01)。研究认为,剧烈运动后血液LA水平与GH水平所表现出的相关性有可能是两者与运动强度的相关,安静时低BG所引起的GH分泌增多取决于中枢对BG代谢的利用性,而非血液BG水平。     

Centre of pressure sway characteristics during static one-legged stance of athletes from different sports

The frequency of one-legged stance and two-legged stance differs considerably among sports. We therefore expect the balance ability of athletes from different sports to vary. This study compared the sway characteristics during a static one-legged stance of soccer players, basketball players, swimmers, and non-athletes. The centre of pressure sway during one-legged stance of ten male participants representing each of the four groups was measured using a stabilometer. Centre of pressure sway was assessed by four sway factors: sway velocity, anterior-posterior sway, horizontal sway, and high-frequency sway. None of the four groups of participants showed significant differences in body sway between standing on the dominant leg and standing on the non-dominant leg. The soccer players had more high-frequency sway and less anterior-posterior sway and horizontal sway than the basketball players, swimmers, and non-athletes. These results suggest that soccer players have superior ability to maintain a stable one-legged stance. Further study is required to determine how much of the superior balance ability in soccer players is innate and how much is developed through training, as well as to determine the relationship between balance ability and playing performance.     

The effects of fast bowling fatigue and adhesive taping on shoulder joint position sense in amateur cricket players in Victoria,Australia

The impact that muscle fatigue and taping have on proprioception in an applied sporting context remains unclear. The purpose of this study was to investigate disturbances in position sense at the shoulder joint, and asses the effectiveness of adhesive tape in preventing injury and improving performance, after a bout of cricket fast bowling. Among amateur cricket players (N = 14), shoulder position sense, maximum voluntary contraction (MVC) force and bowling accuracy was assessed before and immediately after a fatiguing exercise bout of fast bowling. Participants were tested with the shoulder taped and untapped. Shoulder extension MVC force dropped immediately and 30 min after the exercise (P < 0.05 and P < 0.05, respectively). Position sense errors increased immediately after exercise (P < 0.05), shifting in the direction of shoulder extension for all measurements. Taping had no effect on position errors before exercise, but did significantly reduce position errors after exercise at mid-range shoulder flexion angles (45° and 60°; P < 0.05 and P < 0.05, respectively). Taping had no significant effect on bowling accuracy. These findings may be explained by a body map shift towards a gravity neutral position. Added cutaneous input from the tape is proposed to contribute more to shoulder position sense when muscles are fatigued.     

The influence of hip mobility and quadriceps fatigue on sagittal spinal posture and muscle activation in rugby scrum performance

Rugby Union scrumming puts the spine under a high degree of loading. The aim of the current study was to determine how sagittal hip range of motion and quadriceps fatigue influence force output, spinal posture, and activation of the trunk and quadriceps muscles in rugby scrumming. Measures of sagittal hip flexion/extension range of motion were collected from 16 male varsity and club first XV level participants. Sagittal spine motion (electromagnetic motion capture), trunk and quadriceps activation (electromyography), and applied horizontal compressive force (force plate) were measured during individual machine scrumming. Participants performed a 5-trial scrum block involving 5?s of contact with 1–2?min recovery between each trial. They then performed a fatiguing protocol (wall sit to failure) and immediately returned to the scrum machine to perform another five trials. Though there was no significant influence of fatigue on the horizontal compressive force applied during contact (P?=?.83), there was a 52% increase in cervical flexion (P?P?P?相似文献   

支链氨基酸对赛艇运动员极限运动血葡萄糖异生的影响

目的：探讨补充支链氨基酸（BCAA）对不同负荷运动后及恢复期糖代谢和糖异生的影响。方法；20名赛艇运动员随机分为2组（BCAA组和对照组），BCAA组每天补充支链氨基酸，时间为4周，对照组则补充安慰剂。在实验期间，两组运动员都进行相同负荷的运动训练。4周后，在赛艇测功仪上进行模拟2km和5km的耐力测试，并分别在运动前、运动后即刻和运动后30min取血测定血糖、丙氨酸和乳酸。结果：在耐力极限负荷运动中，BCAA组的血糖只在运动后即刻明显下降（P 〈0．05），而对照组则在运动后即刻和运动后30min都明显低于安静时水平（P〈0．05）。BCAA组血丙氨酸浓度在运动后即刻和运动后30min均明显增加（P，〈0．05），而对照组血丙氨酸浓度则在运动后出现明显的下降（P〈0．05）。BCAA组的血乳酸值在运动后明显低于对照组（P〈0．05）。结论：补充BCAA可促进力竭运动后及恢复期糖的异生、延缓疲劳发生和促进运动后疲劳的消除。     

Repeated high-intensity exercise in professional rugby union

Abstract

The aim of the present study was to describe the frequency, duration, and nature of repeated high-intensity exercise in Super 14 rugby union. Time–motion analysis was used during seven competition matches over the 2008 and 2009 Super 14 seasons; five players from each of four positional groups (front row forwards, back row forwards, inside backs, and outside backs) were assessed (20 players in total). A repeated high-intensity exercise bout was considered to involve three or more sprints, and/or tackles and/or scrum/ruck/maul activities within 21 s during the same passage of play. The range of repeated high-intensity exercise bouts for each group in a match was as follows: 11–18 for front row forwards, 11–21 for back row forwards, 13–18 for inside backs, and 2–11 for outside backs. The durations of the most intense repeated high-intensity exercise bouts for each position ranged from 53 s to 165 s and the minimum recovery periods between repeated high-intensity exercise bouts ranged from 25 s for the back row forwards to 64 s for the front row forwards. The present results show that repeated high-intensity exercise bouts vary in duration and activities relative to position but all players in a game will average at least 10 changes in activity in the most demanding bouts and complete at least one tackle and two sprints. The most intense periods of activity are likely to last as long as 120 s and as little as 25 s recovery may separate consecutive repeated high-intensity exercise bouts. The present findings can be used by coaches to prepare their players for the most demanding passages of play likely to be experienced in elite rugby union.     

Threshold frequency of an electrically induced cramp increases following a repeated,localized fatiguing exercise

Abstract

Though clinical observations and laboratory data provide some support for the neuromuscular imbalance theory of the genesis of exercise-associated muscle cramps, no direct evidence has been published. The purpose of this study was to determine the effect of local muscle fatigue on the threshold frequency of an electrically induced muscle cramp. To determine baseline threshold frequency, a cramp was electrically induced in the flexor hallucis brevis of 16 apparently healthy participants (7 males, 9 females; age 25.1 ± 4.8 years). The testing order of control and fatigue conditions was counterbalanced. In the control condition, participants rested in a supine position for 30 min followed by another cramp induction to determine post-threshold frequency. In the fatigue condition, participants performed five bouts of great toe curls at 60% one-repetition maximum to failure with 1 min rest between bouts followed immediately by a post-threshold frequency measurement. Repeated-measures analysis of variance and simple main effects testing showed post-fatigue threshold frequency (32.9 ± 11.7 Hz) was greater (P < 0.001) than pre-fatigue threshold frequency (20.0 ± 7.7 Hz). An increase in threshold frequency seems to demonstrate a decrease in one's propensity to cramp following the fatigue exercise regimen used. These results contradict the proposed theory that suggests cramp propensity should increase following fatigue. However, differences in laboratory versus clinical fatiguing exercise and contributions from other sources, as well as the notion of a graded response to fatiguing exercise, on exercise-associated muscle cramp and electrically induced muscle cramp should be considered.     

Blood flow restriction reduces time to muscular failure

Abstract

Exercise to failure results in similar muscle protein synthesis responses, independent of intensity. However, low-intensity exercise likely requires more repetitions and individuals with injuries may be incapable of sustaining the mechanical stress to reach failure. The aim of this study was to determine if knee wraps provide a stimulus to decrease time to failure. Twenty healthy individuals participated in a randomized crossover study consisting of three trials. The first trial was used to determine one-repetition maximum (1-RM) on leg extension. Participants were then assigned to a blood flow restriction or control group. After trial 2, participants crossed over to the opposite trial. Knee wraps were placed around the upper thigh of each leg during blood flow restriction. Leg extensions were completed at 30% 1-RM until failure. A rating of perceived exertion was taken after exercise and whole blood samples were taken before, after, and 3 min after exercise for the determination of lactate. Repetitions until failure and total work were significantly lower with practical blood flow restriction compared with the control trial. Metabolic stress as measured by whole blood lactate was higher immediately after muscular failure in the control compared with the blood flow restriction trial, but not so 3 min after exercise. There were no differences in ratings of perceived exertion. In conclusion, knee wraps provide a stimulus for blood flow restriction allowing failure to occur sooner with similar metabolic stress after reperfusion. However, similar perceptual responses despite the lower workload with blood flow restriction may limit its application to the highly motivated.     

Comparison of physiological responses to graded exercise test performance in outrigger canoeing

Abstract

The aim of this study was to establish a graded exercise test protocol for determining the peak physiological responses of female outrigger canoeists. Seventeen trained female outrigger canoeists completed two outrigger ergometer graded exercise test protocols in random order: (1) 25 W power output for 2 min increasing by 7.5 W every minute until exhaustion; and (2) 25 W power output for 2 min increasing by 15 W every 2 min to exhaustion. Heart rate and power output were recorded every 15 s. Expired air was collected continuously and sampled for analysis at 15-s intervals, while blood lactate concentration was measured immediately after and 3, 5, and 7 min after exercise. The peak physiological and performance variables examined included peak oxygen uptake ([Vdot]O_2peak), minute ventilation, tidal volume, ventilatory thresholds 1 and 2, respiratory rate, respiratory exchange ratio, heart rate, blood lactate concentration, power output, performance time, and time to [Vdot]O_2peak. There were no significant differences in peak physiological responses, ventilatory thresholds or performance variables between the two graded exercise test protocols. Despite no significant differences between protocols, due to the large limits of agreement evident between protocols for the peak physiological responses, it is recommended that the same protocol be used for all comparison testing to minimize intra-individual variability of results.     

短距离冲刺跑与中距离重复跑对血氨及血乳酸水平的影响及其特点

6名短跑及8名中跑运动员分别完成300m冲刺跑及2×800m最大速度跑,于运动前5min、完成后即刻、完成后4min直至22min(间隔时间3min)分别采血测定血氨及血乳酸含量。结果显示,300m冲刺跑及2×800m中距离重复跑均可导致机体血氨水平显著增高,血氨水平与运动强度具有正相依存关系,血氨峰值出现的时间以运动后4-7min为多,均滞后于血乳酸峰值。血氨可以作为监测运动强度的敏感指标,并与血乳酸具有显著的相关关系。受试者血氨水平的增高与其机体机能状态及疲劳程度密切相关。     

The acute effects of resistance exercise on the main determinants of blood rheology

The aim of this study was to examine short-term changes in blood rheological variables after a single bout of resistance exercise. Twenty-one healthy males completed three sets of 5?–?7 repetitions of six exercises at an intensity corresponding to 80% of one-repetition maximum (1-RM). The average duration of the exercise bout was 35?min. Venous blood samples were obtained before exercise, immediately after exercise and after 30?min of recovery and analysed for lactate, red blood cell count, haematocrit, haemoglobin, plasma viscosity, fibrinogen, total protein and albumin concentration. Plasma volume decreased 10.1% following resistance exercise. This occurred in parallel with an increase of 5.6%, 5.4% and 6.2% in red blood cell count, haemoglobin and haematocrit; respectively. Plasma viscosity increased from 1.55?±?0.01 to 1.64?±?0.01 mPa?·?s immediately after resistance exercise before decreasing to 1.57?±?0.01 mPa?·?s at the end of the recovery period. Similarly, fibrinogen, albumin and total protein increased significantly following resistance exercise. However, the rises in all these rheological parameters were transient and returned to pre-exercise values by the end of recovery. We conclude that a single session of heavy resistance exercise performed by normal healthy individuals alters blood rheological variables and that these changes are transient and could be attributed to exercise-induced haemoconcentration.     

Three dimensional musculoskeletal modelling of the abdominal crunch resistance training exercise

Abstract

The aim of this study was to evaluate the benefits and limitations of using three dimensional (3D) musculoskeletal modelling (LifeModeler^TM) in assessing the safety and efficacy of exercising on an abdominal crunch resistance training machine. Three anthropometric cases were studied, representing a 5^th percentile female, and 50^th percentile and 95^th percentile male. Results indicated that the LifeModeler^TM default model was capable of solving the forward dynamics simulations without adjustments. The modelling was able to indicate high risk for back injury when performing the abdominal crunch exercise as a result of the unacceptable intervertebral joint loading that occurs during the exercise. Individuals with small anthropometric dimensions such as some females and children cannot be accommodated suitably on the abdominal crunch machine which negatively impacts exercise posture and technique. Hip flexor muscle contribution in the execution of the exercise for the 5^th percentile female was substantial thus reducing the efficacy of the exercise in isolating the abdominal muscles.