Effects of whole-body vibration and resistance training on knee extensors muscular performance

Whole-body vibration (WBV) is being promoted as an efficient complement to resistance training. The aim of this study was to investigate the effects of an 8-week program of WBV in combination with resistance training on knee extensors muscular performance. A group of 29 young adults (25 men, 4 women; age 21.8 ± 1.5) performed a WBV plus resistance training program (WBV + RES) or an identical exercise program in absence of vibration (placebo plus resistance training, PL + RES). Participants were evaluated for anthropometry, muscle strength (half-squat three repetition maximum, 3RM), knee extensors isokinetic dynamometry (180° and 60° s⁻¹) and counter-movement jump (CMJ). After the intervention, percent body fat significantly decreased 2.1% only in WBV + RES (P < 0.001), while muscle mass significantly increased in both groups (P < 0.01): 2.2 and 2.8 kg in PL + RES and WBV + RES, respectively. No significant differences were observed in isokinetic strength or CMJ, and 3RM significantly increased in both groups (P < 0.001): 64.2 kg (52% of baseline) in PL + RES, and 46.9 kg (43%) in WBV + RES. The addition of WBV to resistance training during 8 weeks, in recreationally active young adults, did not result in a larger muscular performance improvement compared to an identical exercise program in absence of vibration. Muscle mass also seemed to be equally affected with or without vibration, yet body fat could be exclusively decreased by WBV. Further research is required to clarify whether WBV, as a complement to resistance training, produces additional specific benefits.     

Fitness efficacy of vibratory exercise compared to walking in postmenopausal women

In this study, we compared the efficacy of 8 months of low-frequency vibration and a walk-based program in health-related fitness. Twenty-seven postmenopausal women were randomly assigned into two groups: whole-body vibration (WBV) group (n = 18) performed three times/week a static exercise on a vibration platform (6 sets of 1-min with 1 min of rest, with a 12.6 Hz of frequency and an amplitude of 3 mm); walk-based program (WP) group (n = 18) performed three times/week a 60-min of walk activity at 70–75% of maximal heart rate. A health-related battery of tests was applied. Maximal unilateral concentric and eccentric isokinetic torque of the knee extensors was recorded by an isokinetic dynamometer. Physical fitness was measured using the following tests: vertical jump test, chair rise test and maximal walking speed test over 4 m. Maximal unilateral isokinetic strength was measured in the knee extensors in concentric actions at 60 and 300°/s, and eccentric action at 60°/s. After 8 months, the WP improved the time spent to walk 4 m (20%) and to perform the chair rise test (12%) compared to the WBV group (P = 0.006, 0.002, respectively). In contrast, the comparison of the changes in vertical jump showed the higher effectiveness of the vibratory exercise in 7% (P = 0.025). None of exercise programs showed change on isokinetic measurements. These results indicate that both programs differed in the main achievements and could be complementary to prevent lower limbs muscle strength decrease as we age [ISRCTN76235671].     

膝骨关节炎与膝关节伸、屈肌群肌力的相关性研究

目的通过研究膝骨关节炎(knee osteoarthritis,KOA)症状及病变阶段与膝关节伸、屈肌群肌力的相关性,探讨KOA患者肌力训练的关键肌群。方法社区募集健康老年人、单膝KOA患者、双膝KOA患者共99位志愿者,应用膝关节等速肌力测试、WOMAC评分、6 min步行测试、CS-30测试,分析志愿者膝关节伸、屈肌群峰力矩与KOA症状、全身有氧运动能力、关节功能等的相关性。结果单膝KOA组患者患侧膝关节伸肌群等速峰力矩显著低于健侧。双膝KOA组患者症状严重侧和症状较轻侧膝关节伸、屈肌群等速峰力矩差异均有统计学意义。双膝KOA组患者膝关节伸肌群等速峰力矩显著低于健康组。KOA患者膝关节伸、屈肌群等速峰力矩与CS-30测试、6 min步行测试均呈正相关,均与年龄呈负相关;膝关节伸肌群等速峰力矩与WOMAC评分的疼痛和功能障碍项呈负相关。结论膝关节伸、屈肌群均与KOA相关,KOA康复过程中不仅需重视股四头肌等伸肌群的训练,而且要兼顾腘绳肌、腓肠肌等屈肌群的训练。     

Strength,Functional Outcome,and Postural Stability After Anterior Cruciate Ligament Reconstruction

OBJECTIVE: To compare postural stability, single-leg hop, and isokinetic strength measurements in subjects after anterior cruciate ligament (ACL) reconstruction with an age- and activity-matched control group. DESIGN AND SETTING: Subjects reported to a sports medicine/athletic training research laboratory for testing. Subjects reported for one testing session for a total test time of 1 hour. SUBJECTS: Twenty subjects with ACL reconstructions (ACLRs) and 20 age- and activity-matched controls were selected to participate in this study. An arthroscopically assisted central one-third bone-patellar tendon procedure was used to repair the ACLs. MEASUREMENTS: We measured concentric and eccentric peak torque (Nm) measurements of the knee extensors and flexors at 120 degrees and 240 degrees /second on an isokinetic dynamometer. Unilateral and bilateral dynamic postural stability was measured as a stability index in the anterior-posterior and medial-lateral planes with the Biodex Stability System. We tested single-leg hop for distance to measure objective function. RESULTS: We found no significant difference between the ACLR and control subjects for stability index or knee-flexion peak torque scores. On the single-leg hop for distance, the ACLR subjects hopped significantly shorter distances with the involved limb than the uninvolved limb. Furthermore, the ACLR subjects' single-leg hop distance was significantly less when the involved limb was compared with the control-group matched involved limb, and the ACLR subjects performed significantly better when the uninvolved limb was compared with the control-group matched uninvolved limb. The ACLR subjects produced significantly greater torque in the uninvolved leg than in the involved leg. In addition, the peak torque was significantly less for the involved limb in the ACLR group when compared with the matched involved limb of the control group. CONCLUSIONS: After ACLR (mean = 18 +/- 10 months), single-leg hop-for-distance scores and quadriceps strength were not within normal limits when compared with the contralateral limb. Our results suggest that bilateral and single-limb postural stability in the ACLR group was not significantly different than the control group at an average follow-up of 18 months after surgery.     

Isokinetic assessment of the hip muscles in patients with osteoarthritis of the knee

OBJECTIVES:

To evaluate the difference in isokinetic strength of hip muscles between patients with knee osteoarthritis (OA) and matched healthy controls, and to establish the correlation between this isokinetic strength and pain and function in patients with knee OA.

METHODS:

25 patients with a diagnosis of unilateral knee OA, 25 patients with bilateral knee OA, and 50 matched controls were evaluated using the visual analog scale for pain, knee Lequesne index, Western Ontario and McMaster Universities questionnaire and an isokinetic test.

RESULTS:

The groups were matched for age, gender and body mass index. The results of the isokinetic test revealed lower peak torque of the hip in patients with OA of the knee than in the control group for all movements studied. Strong correlations were found between the peak torque, visual analog scale and function.

CONCLUSIONS:

Patients with OA of the knee exhibit lower isokinetic strength in the hip muscles than healthy control subjects. Strengthening the muscles surrounding the hip joint may help to decrease pain in people with knee OA. Some correlations between pain/function and peak torque were found.     

Comparison of eccentric and concentric isokinetic exercise testing after anterior cruciate ligament reconstruction

Evaluation of muscle function can be helpful in rehabilitation programs with knee injuries. The purposes of this study were to evaluate muscle performance and functional level through eccentric and concentric isokinetic testing after anterior cruciate ligament reconstruction, and to determine whether eccentric and concentric isokinetic values were correlated with functional level using the Modified Cincinnati Scale (MCS). In order to compare the characteristics of eccentric and concentric parameters, we tested 24 male patients (mean age; 31.1 years) after primary reconstruction of ruptured anterior cruciate ligaments of the knee (mean duration; 20.2 months), at angular velocities of 60 degree/sec using Cybex 6000 isokinetic dynamometer. We also evaluated the functional level using the MCS. The values of peak torque of the involved knee extensors and flexors were significantly lower than the uninvolved limb in all eccentric and concentric tests (p<0.01). The deficiency ratios of peak torque in knee extensors were significantly larger than knee flexors in both eccentric and concentric tests (p<0.01). The MCS was inversely correlated with the deficiency ratio in peak torque of eccentric knee extensors (p<0.05). These results suggest that eccentric knee extensor training is essential to restore the functional capacity of the injured knee and that isokinetic evaluation is necessary to plan rehabilitation programs to correct possible imbalances which may be predispose subjects to future injury.     

等速肌力训练对早中期膝关节骨性关节炎患者膝关节功能的影响

目的 探讨等速肌力训练对早中期膝关节骨性关节炎患者膝关节功能的影响。方法 选取2016年6月~2018年1月天津北大医疗海洋石油医院康复医学科收治的早中期KOA患者90例为研究对象,随机分为观察组及对照组,每组45例。对照组在常规药物治疗基础上给予关节松动训练和威伐光治疗,观察组在对照组治疗基础上增加等速肌力训练。评估所有患者治疗前、治疗后4周视觉模拟评分（VAS）、膝关节主动活动度（AROM）、Lysholm膝关节功能评分,并进行等速肌力测试。结果 与治疗前相比,经4周治疗后所有患者VAS评分、AROM评分、Lysholm膝关节功能评分,峰力矩（PT）、总功量（Tw）均较治疗前有改善,观察组治疗后VAS评分（2.65±0.81）分、AROM评分（92.23±7.83）分、Lysholm膝关节功能评分（76.23±5.42）分、伸肌群PT（67.23±5.42）N·m、屈肌群PT（51.35±4.72）N·m、伸肌群Tw（638.43±202.31）N·m、屈肌群Tw（616.50±210.52）N·m改善均优于对照组的（3.82±0.65）分、（81.98±7.38）分、（67.90±4.22）分、（56.90±4.32）N·m、（41.17±5.13）N·m、（520.32±211.51）N·m、（495.01±197.43）N·m,差异有统计学意义（P＜0.05）。结论 在关节松动训练和威伐光治疗治疗基础上增加等速肌力训练,可更好改善早中期KOA患者关节活动度、疼痛、肌力,进而改善患者膝关节功能及日常生活能力。     

对女子手球运动员膝关节屈伸肌群进行等速测试

目的对广东省女子手球队运动员膝关节进行等速向心测试,探讨手球项目运动员膝关节屈伸肌群等速测试特征,为手球项目运动员的力量训练和相关的体育科研提供参考。方法运用CON-TREX等速测试系统对14名广东省女子手球运动员的膝关节进行等速向心测试,选取相对峰力矩、屈伸肌峰力矩比值、平均功率、总功和疲劳指数5个指标来研究手球项目运动员膝关节屈伸肌群的等速测试特征。选取独立样本t检验比较屈肌和伸肌的测试结果。结果膝关节伸肌相对峰力矩值在慢速测试(60°/s)和快速测试(240°/s)时均明显大于屈肌(P<0.01);女手队员膝关节屈伸肌峰力矩比值在快速测试(240°/s)时为76%左右;膝关节屈伸肌平均功率和总功在慢速测试(60°/s)时表现为伸肌大于屈肌(P<0.01),在快速测试(240°/s)时表现为左膝关节伸肌大于屈肌(P<0.05);女手队员膝关节屈伸肌疲劳指数范围在0～0.49之间。结论女手队员膝关节伸肌的最大力量和快速力量大于屈肌;女手队员膝关节屈伸肌峰力矩比值在快速测试(240°/s)时略微偏低,说明女手队员膝关节屈肌快速力量偏低;女手队员膝关节伸肌的快速力量和肌肉工作能力均大于屈肌;女手队员膝关节屈伸肌疲劳指数偏低,说明女手队员膝关节屈伸肌的力量耐力水平比较低。     

髌腱末端病运动员膝关节屈伸峰力矩和表面肌电图的特征☆

背景：髌腱末端病是腱止点部位的微细损伤,股四头肌群中的股内侧肌与股外侧肌之间的力量平衡发生变化,可直接导致髌骨产生异常运动从而对腱止点部位产生影响。 目的：分析髌腱末端病发生机制和髌腱末端病对膝关节及其周围肌肉活动产生的影响。 方法：选择10名患有髌骨肌腱病的男运动员及10名运动项目、身高和年龄匹配的正常男运动员,采用瑞士CON-TREX等速肌力测试与训练系统,分别进行膝关节力量和表面肌电图的测试,比较与分析膝关节屈肌力矩、伸肌力矩和股四头肌表面肌电图的变化。 结果与结论：发现在等长运动时,末端病组的伸肌伸肌峰力矩明显小于对照组、峰值转矩比比值明显大于对照组;在等速运动时,末端病组的伸肌伸肌峰力矩明显小于对照组,并随着运动角速度增加而变化显著,而峰值转矩比比值均不同程高于对照组;末端病组的股内侧肌/股外侧肌的整合肌电图比值在等长运动和等速运动时,均明显低于对照组。提示髌腱末端病运动员膝关节屈肌与伸肌的力量差距较为突出,存在股内侧肌活动低下和股内侧肌与股外侧肌之间不平衡的现象。     

Voluntary activation of the ankle plantar flexors following whole-body vibration

This study investigated the effect of whole-body vibration (WBV) on the voluntary activation of the ankle plantar flexors. Twelve healthy young adults were randomly exposed to two treatments on separate occasions. The first (non-WBV) involved stretching of the plantar flexors at end range of dorsiflexion for five 1-min bouts. The second involved the same stretch with WBV (26 Hz) for five 1-min bouts. Attempted maximal voluntary contractions (AMVCs) of the plantar flexors were performed on an isokinetic dynamometer (30° s⁻¹) before and after each treatment. A twitch interpolation technique was used to investigate voluntary activation. Post-treatment data were normalised against pre-treatment data. Subjects were classified as maximally (n = 6) or sub-maximally (n = 6) activated using the pre-treatment twitch interpolation data. The effects of WBV were assessed by repeated measure (RM) MANOVA. After WBV, the group of subjects classified as sub-maximally activated increased peak voluntary torque and rate of voluntary torque production (P < 0.05), whereas angular displacement to peak torque reduced (P < 0.05); i.e. peak torque was produced at a longer muscle length. No significant non-WBV treatment effects were found for this group. No significant WBV effects were found for the group of subjects classified as maximally activated. This study found that the response to WBV was dependent on the level of voluntary activation of the ankle plantar flexors during a set of AMVCs.     

女子曲棍球运动员膝关节屈伸肌群等速测试与分析

背景：等速测试系统已广泛应用来评价不同项目运动员关节肌群的力量特征。 目的：测试广东省女子曲棍球运动员的膝关节进行等速向心,观察曲棍球项目运动员膝关节屈伸肌群的等速向心测试力量特征。 方法：运用CON-TREX等速测试系统对广东省14名现役女子曲棍球运动员的膝关节进行等速向心测试。检测指标为相对峰力矩、关节肌群屈伸肌峰力矩比值、平均功率、总功和疲劳指数。 结果与结论：在60 (°/s)慢速测试时,女子曲棍球队员的两侧膝关节肌群相对峰力矩值表现为伸肌大于屈肌(P < 0.01);左膝关节屈伸肌峰力矩比值在3种不同测试速度下的范围为66%~77%,右膝关节屈伸肌峰力矩比值为82%~88%;左膝关节伸肌平均功率值均大于屈肌(P < 0.01);左右膝关节伸肌的总功值均大于屈肌(P < 0.01);膝关节屈伸肌疲劳指数范围在0.24~0.48之间。膝关节伸肌的最大力量大于屈肌,屈伸肌峰力矩比值在240 (°/s)快速测试时略微偏低,而右膝关节屈伸肌峰力矩比值在慢速测试时偏高,说明女子曲棍球队员左膝关节屈肌快速力量偏低,右膝关节伸肌最大力量比较低,伸肌的快速力量大于屈肌,伸肌的工作能力强于屈肌,屈伸肌的力量耐力水平比较低。     

Whole-body vibration and the prevention and treatment of delayed-onset muscle soreness

Context:

Numerous recovery strategies have been used in an attempt to minimize the symptoms of delayed-onset muscle soreness (DOMS). Whole-body vibration (WBV) has been suggested as a viable warm-up for athletes. However, scientific evidence to support the protective effects of WBV training (WBVT) on muscle damage is lacking.

Objective:

To investigate the acute effect of WBVT applied before eccentric exercise in the prevention of DOMS.

Design:

Randomized controlled trial.

Setting:

University laboratory.

Patients or Other Participants:

A total of 32 healthy, untrained volunteers were randomly assigned to either the WBVT (n  =  15) or control (n  =  17) group.

Intervention(s):

Volunteers performed 6 sets of 10 maximal isokinetic (60°/s) eccentric contractions of the dominant-limb knee extensors on a dynamometer. In the WBVT group, the training was applied using a vibratory platform (35 Hz, 5 mm peak to peak) with 100° of knee flexion for 60 seconds before eccentric exercise. No vibration was applied in the control group.

Main Outcome Measure(s):

Muscle soreness, thigh circumference, and pressure pain threshold were recorded at baseline and at 1, 2, 3, 4, 7, and 14 days postexercise. Maximal voluntary isometric and isokinetic knee extensor strength were assessed at baseline, immediately after exercise, and at 1, 2, 7, and 14 days postexercise. Serum creatine kinase was measured at baseline and at 1, 2, and 7 days postexercise.

Results:

The WBVT group showed a reduction in DOMS symptoms in the form of less maximal isometric and isokinetic voluntary strength loss, lower creatine kinase levels, and less pressure pain threshold and muscle soreness (P < .05) compared with the control group. However, no effect on thigh circumference was evident (P < .05).

Conclusions:

Administered before eccentric exercise, WBVT may reduce DOMS via muscle function improvement. Further investigation should be undertaken to ascertain the effectiveness of WBVT in attenuating DOMS in athletes.     

The effects of whole body vibration on balance,joint position sense and cutaneous sensation

Whole body vibration (WBV) may enhance muscular strength and power but little is known about its influence on sensory-motor function. Vibration of a single muscle or tendon affects the afferent system in a manner that depends on amplitude and frequency. WBV stimulates many muscle groups simultaneously and the frequencies and amplitudes used are different from many of the studies on single musculotendinous units. We investigated the effects of WBV at two amplitudes on balance, joint position sense (JPS) and cutaneous sensation in young healthy subjects. Eighteen adults (24.3 ± 1.5 years, 15 females) were assessed before WBV (five 1 min bouts, 30 Hz) then immediately, 15 and 30 min afterwards. Two amplitudes (4 and 8 mm peak to peak) were investigated on different occasions. Standing balance was assessed with feet together and eyes closed, and standing on one leg with eyes open and closed. JPS at the knee and ankle was assessed by repositioning tasks while cutaneous sensation was recorded from six sites in the lower limb using pressure aesthesiometry. Neither amplitude affected JPS (P > 0.05). There were minimal effects on balance only in the vertical plane and only 30 min after WBV (P < 0.05). Low amplitude vibration only reduced sensation at the foot and ankle immediately after WBV (P < 0.008). High amplitude vibration impaired sensation at the foot, ankle and posterior shank for the entire test period (P < 0.008). In young healthy individuals WBV did not affect JPS or static balance, but reduced cutaneous sensation. These data may have implications for older and clinical populations with compromised postural control.     

Similar increases in muscle size and strength in young men after training with maximal shortening or lengthening contractions when matched for total work

Training exclusively with eccentric (lengthening) contractions can result in greater muscular adaptations than training with concentric (shortening) contractions. We aimed to determine whether training-induced increases in muscle size and strength differed between muscles performing maximal lengthening (LC) or maximal shortening (SC) contractions when total external work is equivalent. Nine healthy young males completed a 9-week isokinetic (0.79 rad/s) resistance training program of the elbow flexors whereby they performed LC with one arm and an equivalent volume of total external work with the contralateral arm as SC. Training increased isometric peak torque for both LC (~10%) and SC (~20%) with no difference (P = 0.14) between conditions. There were also similar increases in isokinetic peak torque at both slow (0.79 rad/s) and fast (5.24 rad/s) shortening and lengthening peak torque for both LC (~8–10%) and SC (~9–20%). Training increased work per repetition similarly for both LC (~17%) and SC (~22%), in spite of ~40% greater work per repetition with LC. The increase in muscle cross-sectional area with training was also similar (P = 0.37) between LC (~6.5%) and SC (~4.6%). We conclude that increases in muscle size and strength with short-term unilateral resistance training are unrelated to muscle contraction type when matched for both exercise intensity (i.e. maximal contractions) and total external work.     

The effects of 11 weeks whole body vibration training on jump height,contractile properties and activation of human knee extensors

The purpose of the present study was to investigate whether 11 weeks of whole body vibration (WBV) training applied in a way that is commonly seen in practice, i.e. without additional loads, would improve muscle activation and/or contractile properties of the knee extensor muscles and counter movement jump height in healthy subjects. Ten subjects belonging to the experimental group trained three times a week and stood bare-foot with a 110 ° knee angle on a vibration platform (30 Hz, 8 mm amplitude). They underwent five to eight sets of 1-min vibration with 1 min rest in between. Ten control subjects followed the same training programme but stood (110 ° knee angle) beside the platform. Before, during and following the training period the subjects were tested. Values [mean (SEM)] obtained in the last test were expressed as percentages of the baseline value and presented for control and experimental groups. Quadriceps femoris isometric muscle force [105.4 (6.2)%, 99.9 (2.0)%; P=0.69], voluntary activation [107.1 (6.0)%, 101.1 (2.3)%; P=0.55] and maximal rate of voluntary force rise [95.4 (6.0)%, 103.3 (7.7)%; P=0.57] did not improve. The maximal rate of force rise during electrical stimulation was increased [102.3 (4.5)%, 123.6 (7.5)%; P=0.02]. Counter movement jump height was not affected by WBV [103.7 (1.8)%, 103.0 (2.8)%; P=0.71]. In conclusion, 11 weeks of standard two-legged WBV training without additional training loads did not improve functional knee extensor muscle strength in healthy young subjects.     

等速限弧运动对膝关节炎功能影响

目的　探讨股四头肌限弧等速运动角度对膝骨性关节炎患者的疗效。 方法　共78例右膝骨性关节炎患者纳入研究，按随机法赋值从大到小分成3组，每组26例。3组除常规运动训练外，进行不同角度的限弧等速运动训练。训练弧度分别为：A组膝屈90°→10°，B组膝屈60°→10°，C组膝屈30°→10°。每周3 次, 训练 8 周。在治疗前后分别采用疼痛视觉模拟评分法（VAS）评估疼痛改善程度，采用美国特种外科医院（HSS）指数评定膝关节功能情况，同时等速训练仪测定患膝峰力矩（peak torque，PT）、本体感觉误差均值。 结果　3组疼痛、HSS指数、PT较治疗前差异有显著性意义（P <0.05），A组优于B组、C组（P <0.05）；治疗后各组本体感觉较治疗前略有改善，但3组改善程度无统计学差异（P> 0.05）。 结论　不同弧度等速运动可以改善膝关节功能，较大弧度的限弧等速运动获益更明显。     

Effects of whole-body vibration exercise on muscular strength and power,functional mobility and self-reported knee function in middle-aged and older Japanese women with knee pain

BackgroundWhole-body vibration training using vertical-vibration machines is called “acceleration training” (AT). The purpose of this study was to elucidate the effect of AT on lower-limb muscular strength and power, functional mobility and self-reported knee function in middle-aged and older Japanese women with knee pain.MethodsThirty-eight middle-aged and older Japanese women (aged 50–73 years) with knee pain were divided into two groups: (1) the AT group (n = 29) engaged in AT three times per week for eight weeks, and (2) the control group (C group, n = 9). The AT program consisted of flexibility training, strength training of mainly the quadriceps and surrounding muscles and cool-down exercises. The C group was encouraged to perform the same or similar exercises at home without vibratory stimulus. We evaluated knee strength and power, functional mobility (timed up and go: TUG) and self-reported knee function (Japanese Knee Osteoarthritis Measure: JKOM).ResultsNo one in the AT group dropped out during the program. All JKOM categories except degree of pain improved significantly post intervention indicating improved knee function, and TUG was significantly shorter in these participants. All knee strength and power parameters except isometric knee extension peak torque improved significantly. The degree of change in JKOM total score and TUG was significantly different between the two groups.ConclusionVibratory stimulus during an eight week AT programme can promote participation and safely improve functional mobility and self-reported knee function better than exercise without vibratory stimulus in middle-aged and older Japanese women with knee pain.Level of evidence: level 2.     

Neuromuscular fatigue induced by whole-body vibration exercise

The aim of this study was to examine the magnitude and the origin of neuromuscular fatigue induced by half-squat static whole-body vibration (WBV) exercise, and to compare it to a non-WBV condition. Nine healthy volunteers completed two fatiguing protocols (WBV and non-WBV, randomly presented) consisting of five 1-min bouts of static half-squat exercise with a load corresponding to 50 % of their individual body mass. Neuromuscular fatigue of knee and ankle muscles was investigated before and immediately after each fatiguing protocol. The main outcomes were maximal voluntary contraction (MVC) torque, voluntary activation, and doublet peak torque. Knee extensor MVC torque decreased significantly (P < 0.01) and to the same extent after WBV (?23 %) and non-WBV (?25 %), while knee flexor, plantar flexor, and dorsiflexor MVC torque was not affected by the treatments. Voluntary activation of knee extensor and plantar flexor muscles was unaffected by the two fatiguing protocols. Doublet peak torque decreased significantly and to a similar extent following WBV and non-WBV exercise, for both knee extensors (?25 %; P < 0.01) and plantar flexors (?7 %; P < 0.05). WBV exercise with additional load did not accentuate fatigue and did not change its causative factors compared to non-WBV half-squat resistive exercise in recreationally active subjects.     

Neuromuscular adaptations to 8-week strength training: isotonic versus isokinetic mode

Previous studies attempted to compare the effectiveness of isokinetic and isotonic training. However, they have provided conflicting results. The purpose of this study was to compare the effects of isotonic versus isokinetic standardized concentric strength training programs of the knee extensors on the neuromuscular system. The standardization of these two training programs was ensured by the equalization of the total external amount of work performed and the mean angular movement velocity. Thirty healthy male students were randomly assigned to the isotonic (IT; n = 11), the isokinetic (IK; n = 11) or the control (C; n = 8) group. Both IT and IK groups trained their dominant lower leg 3 sessions/week for 8 weeks on a dynamometer. The IT group exercised using a preset torque of 40% of the maximal voluntary isometric torque at 70° (0° = leg in horizontal position). The IK group exercised at a velocity ranging between 150° and 180° s^?1. Isotonic, isokinetic and isometric tests were performed on a dynamometer before and after strength training. Surface electromyographic activity of vastus lateralis, vastus medialis, rectus femoris, semitendinosus and biceps femoris muscles was recorded during the tests. Significant strength increases in both dynamic and static conditions were noticed for IT and IK groups without any significant difference between the two trained groups. Agonist muscle activity also increased with training but no change in antagonist muscle co-activity was observed. The two training methods could be proposed by clinicians and athletic coaches to improve concentric muscle strength in dynamic and static conditions.     

Strength training improves cycling efficiency in master endurance athletes

The purpose of this study was to test the effect of a 3-week strength training program of knee extensor muscles on cycling delta efficiency in master endurance athletes. Nine master (age 51.5 ± 5.5 years) and 8 young (age 25.6 ± 5.9 years) endurance athletes with similar training levels participated in this study. During three consecutive weeks, all the subjects were engaged in a strength training program of the knee extensor muscles. Every week, they performed three training sessions consist of 10 × 10 knee extensions at 70% of maximal repetition with 3 min rest between in a leg extension apparatus. Maximal voluntary contraction torque (MVC torque) and force endurance (End) were assessed before, after every completed week of training, and after the program. Delta efficiency (DE) in cycling was evaluated before and after the training period. Before the training period, MVC torque, End, and DE in cycling were significantly lower in masters than in young. The strength training induced a significant improvement in MVC torque in all the subjects, more pronounced in masters (+17.8% in masters vs. +5.9% in young, P < 0.05). DE in cycling also significantly increased after training in masters, whereas it was only a trend in young. A significant correlation (r = 0.79, P < 0.01) was observed between MVC torque and DE in cycling in masters. The addition of a strength training program for the knee extensor muscles to endurance-only training induced a significant improvement in strength and cycling efficiency in master athletes. This enhancement in muscle performance alleviated all the age-related differences in strength and efficiency.