健康男女青年前臂旋前、旋后肌群力量的研究

目的 :(1 )通过测试健康男女青年前臂旋肌群的力量 ,为运动训练、损伤和康复提供数据和科学依据 ;(2 )探讨健康青年前臂旋肌群的生物力学规律。方法 :利用CYBEX -60 0 0测力系统对健康男女青年前臂旋前、旋后肌群进行等长和等速测试。结果发现 ,在等长测试中 ,男女旋后肌群峰力矩随着测量角度的增加而减少、旋前肌群峰力矩随着测量角度增加而增加。在等速向心测试中 ,男女旋前、旋后肌群的峰力矩随着所测角速度的增加而减少。两种测试均表明旋前肌群峰力矩要大于旋后肌群的峰力矩 (P <0 0 5 )。男性与女性相比绝对力矩较大 (P <0 0 5 ) ,但去除体重因素后 ,男女力矩间的差距缩小。结果表明 ,用相对峰力矩比较男女间的差别更为合理。通过测试发现健康男女青年前臂旋的力量较薄弱 ,这可能与平时前臂旋肌锻炼少有关     

机械性踝关节不稳患者踝屈、伸肌群等速肌力评价

目的:评价机械性踝关节不稳(mechanical ankle instability,MAI)患者踝屈、伸肌群的等速肌力。方法:20名单侧机械性踝关节不稳患者的双侧踝关节分别接受等速肌力测试(60°/s和120°/s)。比较患侧和健侧踝关节屈、伸肌群相对峰力矩、平均功率、总功和屈伸力矩比的差异。结果:60°/s时,两侧伸肌群相对峰力矩、平均功率及总功的差别均无统计学意义(P=0.303,P=0.548,P=0.452),屈肌群相对峰力矩、平均功率和屈伸力矩比均无显著性差异(P=0.417,P=0.275,P=0.870),但屈肌群总功有显著性差异(P=0.043)。120°/s时,两侧伸肌群相对峰力矩、平均功率及总功差别均无统计学意义(P=0.096,P=0.069,P=0.233),但屈肌群相对峰力矩、平均功率、总功和屈伸力矩比有显著性差异(P=0.030,P=0.043,P=0.017,P=0.036)。结论:机械性踝关节不稳患者患侧踝关节跖屈肌群快速运动时肌力下降,这可能与其踝关节稳定性有关。     

膝关节屈肌和伸肌等速向心、等速离心及等长测试的研究

本文通过运用Ｃｙｂｅｘ－６０００型等速测力系统对２５名健康男青年膝屈肌和伸肌进行等速向心、等速离心及等长测试，来比较膝肌肉向心收缩、离心收缩和等长收缩的功能，并探讨其相互间的关系。结果表明：等速测试时，膝屈肌和伸肌离心收缩的肌力明显大于向心收缩。在膝屈曲６０°时，离心收缩和等长收缩的肌力同样明显大于向心收缩，但离心收缩与等长收缩相比无显著性差异。随运动速度增加，屈肌和伸肌向心收缩的肌力明显下降，而离心收缩的肌力无明显变化。     

强化训练对士兵踝关节肌力和跟腱横截面积的影响

目的评价踝关节强化训练对士兵踝关节肌力的影响,找到合适的、能快速提高训练成绩的训练方法。方法随机挑选新入伍的士兵和第二年度兵各30名,并对新兵专门添加为期8周的踝关节背伸、跖屈、内外翻的肌力强化训练,然后采用CYBEX-6000型等速测试训练系统分别对训练前、强化训练8周时的新兵和第二年度兵进行踝关节肌力等速测试和跟腱横截面积测量。结果新兵训练前、强化训练8周后、第二年度士兵的跟腱横截面积(分别为0·64±0·05cm2、0·67±0·07cm2、0·65±0·07cm2)与体重呈正相关(r=0·446),消除体重因素后,各组间无明显差异(P=0·698,F=0·361);训练前的踝关节背伸、跖屈、内外翻的峰力矩、力矩加速能、耐力、屈伸峰力矩之比等指标均明显低于强化训练8周组和第二年度士兵组(P<0·05或0·01)而强化组和第二年度兵组之间无明显差异(P>0·05)。结论新兵8周强化训练能取得与经常规训练的第二年度兵接近的效果,即强化训练可以在短期内快速促进体能储备,从而提高训练成绩;训练后跟腱截面积无明显变化,提示踝关节肌力的提高不是通过肌腱肥大实现的,而与肌腱的功能结构塑形改建有关。     

正常男性膝关节等速向心收缩力矩比较研究

利用ＢＩＯＤＥＸ多关节等速测试及康复系统,测试了２０例正常男性两侧膝关节的等速向心收缩的力矩资料,并进行了比较,结果表明：峰力矩及相对峰力矩两膝无差异,随速度增加而减少;到达峰力矩时间亦随速度增加而减少;屈肌／伸肌值随速度增加而增加。     

优秀击剑运动员下肢三关节等速肌力测试分析

目的:研究我国优秀击剑运动员下肢髋、膝、踝三关节肌群等速肌力表现,找出薄弱肌群。方法:国家击剑队备战2008年奥运会重点队员26名,男女各13名,年龄23.1±2.36岁。在60°/s、240°/s速度下测定运动员双侧下肢髋、膝、踝屈伸肌群等速向心峰力矩。结果发现:(1)髋关节:在240°/s下双侧伸肌峰力矩均明显低于60°/s(P<0.05),60°/s和240°/s下双侧髋关节屈肌峰力矩无显著差异(P>0.05);男运动员两个速度下前腿伸肌峰力矩均显著高于后腿(P<0.05),女运动员无显著差异(P>0.05);两个速度下,运动员双腿屈伸肌峰力矩比值低于正常。(2)膝关节:60°/s时男运动员双腿屈伸肌峰力矩有显著差异(P<0.05),240°/s时双侧伸肌峰力矩有显著差异(P<0.05),女运动员两个速度下均无显著差异(P>0.05);60°/s时,女运动员前后腿屈伸肌峰力矩比值分别为0.56和0.54,男运动员分别为0.63和0.67;240/°s时男女前后腿屈伸肌峰力矩比值均在正常范围。(3)踝关节:60°/s时男运动员前腿踝关节屈伸肌峰力矩显著大于后腿(P<0.05),240°/s时无显著差异(P>0.05);两个速度下,女运动员踝关节屈伸肌峰力矩均无显著性差异(P>0.05);运动员踝关节屈伸峰力矩比值在两个速度下均低于正常。结论:优秀男子击剑运动员下肢关节等速肌力双侧不对称,女运动员不对称表现不明显;击剑运动员下肢薄弱肌群为后腿髋关节伸肌群、股后肌群、前腿股后肌群及踝关节背伸肌群。     

人体跖趾关节活动受限对行走时下肢生物力学特征的影响

目的:分析跖趾关节活动受限对行走时下肢生物力学特征的影响。方法:10名普通男性大学生分别完成正常和跖趾关节受限情况下的步行,同步采集运动学、动力学及下肢主要肌肉的表面肌电信号。计算髋、膝、踝的三维角度、关节净力矩、关节功率和关节功,计算各肌肉摆动相和支撑相的肌电均方根振幅(RMS)并获得肌电的线性包络线。结果:与正常步行比较,限制跖趾关节行走时步宽显著增大(P=0.032),摆动相百分比显著增大(P=0.002),支撑相百分比显著减小(P=0.002),步长、步频两组之间无显著性差异(P>0.05)。跖趾关节受限情况下,踝最大背屈角度显著增大(P<0.001),最大跖屈角度显著减小(P<0.001);踝关节最大跖屈力矩(P<0.001)、最大背屈力矩(P=0.029)显著增大;踝关节功率最大值增大(P<0.001)、最小值显著减小(P<0.001);踝关节负功显著增大(P<0.001),正功受限和正常两种情况无显著性差异(P>0.05)。膝关节和髋关节各指标在受限和正常两种情况下均无显著性差异(P>0.05)。支撑相腓肠肌内侧头RMS值受限情况显著大于正常情况(P=0.009),其他肌肉两组间均无显著性差异(P>0.05)。结论:在跖趾关节运动受到约束后,人体主要是通过踝关节增大背屈角度、增加做功和增大周围肌肉的活动水平来代偿,以保持步长、步速和运动中的动态平衡。限制跖趾关节会增加行走时人体足踝部分的能量消耗,长期受限,可能会导致小腿后群肌肉的疲劳或损伤。     

慢性踝关节不稳患者三维步态动力学特征

目的:研究慢性踝关节不稳患者步态的三维动力学特征,探讨其运动功能变化及生物力学机制。方法:选择慢性踝关节不稳患者15名(实验组),依据其年龄、身高、体重匹配健康受试者15名(对照组)。采用三维动作捕捉系统和Visual 3D软件观测受试者步行时支撑期地面反作用力(GRF)及踝关节力矩的变化。结果:实验组在矢状轴、额状轴和垂直轴的GRF第1峰值较对照组差异均无统计学意义(P>0.05),但3个轴向的GRF第2峰值均较对照组小,其中矢状轴向前和垂直轴向上的GRF差异具有统计学意义(P<0.01)。踝关节力矩于矢状面、额状面、水平面的第1峰值分别是背伸、内翻和内收力矩,实验组较对照组差异均无统计学意义(P>0.05)。踝关节力矩于3个面的第2峰值分别是跖屈、外翻和外展力矩,实验组均较对照组小,其中跖屈和外展力矩差异具有统计学意义(P<0.05)。结论:慢性踝关节不稳患者步行过程中,于支撑末期向上、向前的地面反作用力以及踝跖屈、外展力矩降低,这可能是踝跖屈、外翻肌群肌肉功能不足所致,但导致踝关节跖屈功能不足的主要肌群尚需进一步明确。     

太极拳锻炼对老年人下肢肌力影响的研究

本研究采用太极拳运动作为干预因子 ,探讨太极拳运动对老年人下肢肌肉力量的影响 ,为老年人正确锻炼下肢肌肉力量以及太极拳抗衰老机理提供实验依据。采用CybexII+ 等速肌力测试系统 ,对经过 1 6周太极拳练习的 65～ 70岁老人的膝关节屈、伸肌群力量进行标准化、定量化测量 ,实验结果表明 ,男、女运动组屈、伸膝肌群耐力 (ER)均显著高于对照组 ,运动组自身前后对照显示 ,各项肌力指标除屈、伸肌爆发力 (TAE)外均出现显著性差异     

中国女子篮球运动员膝关节等速肌力测试分析

目的:了解中国国家女子篮球队运动员膝关节等速肌力特征。方法:选用IsoMed 2000等速测试系统,采用60°/s、180°/s、240°/s三种角速度,测试18名中国女篮国家队运动员膝关节等速肌力。根据场上位置将运动员分为三组:后卫组7人(1、2号位),前锋组6人(3、4号位),中锋组5人(5号位),比较分析三组运动员的测试结果。结果:(1)女篮运动员双侧膝关节慢速测试时(60°/s)屈伸肌峰力矩(PT)显著高于快速测试(180°/s,240°/s),膝关节屈伸肌峰力矩比值(H/Q)随测试速度增加递增,左右膝H/Q无显著性差异。(2)慢速测试时(60°/s),左右膝关节峰力矩、峰力矩/体重比值、平均功率、H/Q无显著差异。(3)快速测试(240°/s)时,左膝屈肌PT、峰力矩/体重比值(PT/BW)显著高于右膝。180°/s测试时,左膝屈肌平均功率显著高于右膝。(4)60°/s测试时,后卫、前锋、中锋运动员PT、PT/BW组间比较无显著性差别。180°/s测试时,后卫运动员左膝屈肌PT与前锋、中锋运动员比较有显著性差异(P=0.02),各组间伸肌PT未见显著差异。240°/s测试时,后卫运动员右膝屈、伸肌PT/BW和中锋运动员比较均存在显著差异;后卫、前锋、中锋三组运动员平均功率、H/Q、总功与峰值功率组间比较均无显著性差别。结论:(1)女篮运动员快速测试(240°/s)时左膝屈肌力量强于右膝,反映快速运动时左右膝关节肌力不平衡。(2)不同场上位置女篮运动员膝关节等速肌力快速测试结果有差异性,提示力量训练应根据场上位置进行特异性训练。(3)女篮运动员需加强屈肌快速力量训练,以提高H/Q,预防膝关节损伤。     

Prevention of disuse muscular weakness by restriction of blood flow

PURPOSE: The aim of the present study was to compare the effects of periodic restriction of blood flow to lower extremities with those of isometric exercise on disuse muscular atrophy and weakness induced by immobilization and unloading. METHODS: The left ankle of each of 15 healthy males was immobilized for 2 wk using cast, and subjects were instructed to walk using crutches with non-weight bearing during this period. Subjects were divided into three groups: a restriction of blood flow (RBF) group (application of external compressive force of 200 mm Hg for 5 min followed by 3 min of rest, repeated five times in a single session, two sessions per day for 14 d); an isometric training (IMT) group (20 "exercises" of 5-s isometric contraction of the knee extensor, flexor, and ankle plantar flexor muscles followed by rest, twice a day, daily for 2 wk); and a control (CON) group (no intervention). We measured changes in muscle strength, thigh/leg circumferences, and serum growth hormone levels. RESULTS: Immobilization/unloading resulted in significant decreases in muscle strength of knee extensor and flexor muscles (P < 0.01 and < 0.05, respectively) and thigh and leg circumferences (P < 0.05, each) in the CON group, and significant decreases in muscle strength of the knee flexor muscles, ankle plantar flexor muscles, and leg circumference (P < 0.05) in the IMT group. RBF protected against these changes in muscle strength and thigh/leg circumference (P < 0.01 and < 0.05, respectively). No changes in serum growth hormone levels were noted. CONCLUSION: Our results indicate that repetitive restriction of blood flow to the lower extremity prevents disuse muscular weakness.     

Acute effects of passive stretching vs vibration on the neuromuscular function of the plantar flexors

This study examined the acute effects of passive stretching (PS) vs prolonged vibration (VIB) on voluntary peak torque (PT), percent voluntary activation (%VA), peak twitch torque (PTT), passive range of motion (PROM), musculotendinous stiffness (MTS), and surface electromyographic (EMG) and mechanomyographic (MMG) amplitude of the medial gastrocnemius (MG) and soleus (SOL) muscles during isometric maximal voluntary contractions (MVCs) of the plantar flexors. Fifteen healthy men performed the isometric MVCs and PROM assessments before and after 20 min of PS, VIB, and a control (CON) conditions. There were 10% and 5% decreases in voluntary PT, non-significant 3% and 2% decreases in %VA, 9–23% decreases in EMG amplitude of the MG and SOL after the PS and VIB, respectively, with no changes after the CON. PROM increased by 19% and MTS decreased by 38% after the PS, but neither changed after the VIB or CON conditions. Both PS and VIB elicited similar neural deficits (i.e., γ loop impairment) that may have been responsible for the strength losses. However, mechanical factors related to PROM and MTS cannot be ruled out as contributors to the stretching-induced force deficit.     

Ankle dorsiflexors and plantarflexors neuromuscular electrical stimulation training impacts gait kinematics in older adults: A pilot study

BackgroundWhile ankle muscles, highly affected by aging, are highly implicated in the changes in gait kinematics and involved in the limitation of seniors' mobility, whether neuromuscular electrical stimulation (NMES) training of these muscles could impact gait kinematics in older adults has not been investigated yet.Research questionWhat are the effects of 12 weeks of ankle plantar and dorsiflexors NMES training on strength and gait kinematics in healthy older adults?MethodsFourteen older adults (73.6 ± 4.9 years) performed a three-time per week, three months long NMES training of both ankle plantar and dorsiflexors. Before and after training, neuromuscular parameters, gait kinematic parameters, and daily physical activity were measured.ResultsThe participants significantly increased their lower limb muscle mass and their plantar and dorsiflexors isometric strength after training. They reduced the hip abduction/adduction and the pelvic anterior tilt range of motion and variability during gait. However, the participants became less active after the training.SignificanceNMES training of ankle muscles, by increasing ankle muscle mass and strength,modified gait kinematics. NMES training of ankle muscles is feasible and effective to lower the hip implication and increment foot progression angle during gait. Further study should determine if this could lower the risk of falling.     

Plantar calcaneal enthesophytes: new observations regarding sites of origin based on radiographic,MR imaging,anatomic, and paleopathologic analysis

OBJECTIVE: To determine the relationship between sites of calcaneal plantar enthesophytes and surrounding fascial and soft tissue structures using routine radiography, MR imaging, and data derived from cadaveric and paleopathologic specimens. DESIGN AND PATIENTS: Two observers analyzed the MR imaging studies of 40 ankles in 38 patients (35 males, 3 females; mean age 48.3 years) with plantar calcaneal enthesophytes that were selected from all the ankle MR examinations performed during the past year. Data derived from these MR examinations were the following: the size of the enthesophyte; its location in relation to the plantar fascia (PF) and flexor muscles; and the thickness and signal of the PF. The corresponding radiographs of the ankles were evaluated at a different time by the same observers for the presence or absence of plantar enthesophytes and, when present, their measurements. A third observer reviewed all the discordant observations of MR imaging and radiographic examinations. Two observers analyzed 22 calcaneal specimens with plantar enthesophytes at an anthropology museum to determine the orientation of each plantar enthesophyte. MR imaging of a cadaveric foot with a plantar enthesophyte with subsequent sagittal sectioning was performed to provide further anatomic understanding. RESULTS: With regard to MR imaging, the mean size of the plantar enthesophytes was 4.41 mm (SD 2.4). Twenty (50%) enthesophytes were located above the PF, 16 (40%) between the fascia and abductor digiti minimi, flexor digitorum brevis and abductor hallucis muscles, and only one (3%) was located within the PF. In three (8%) cases the location was not determined. The size of enthesophytes seen with MR imaging and radiographs was highly correlated (P<0.01). The interobserver agreement for all measurements was good (Pearson >0.8, kappa >0.9). Eleven of the 22 bone specimens had plantar enthesophytes oriented in the direction of the abductor digiti minimi and 11 oriented in the direction of the flexor digitorum brevis and PF. The cadaveric sections revealed different types of enthesophytes. CONCLUSIONS: Plantar calcaneal enthesophytes arise in five different locations: at the insertion sites of abductor digiti minimi and flexor digitorum brevis muscles; between the PF and these muscles; and, less frequently, within the PF and at the insertion site of the short plantar ligament.     

Effects of plyometric and weight training on muscle-tendon complex and jump performance

PURPOSE: The purpose of this study was to investigate the effects of plyometric and weight training protocols on the mechanical properties of muscle-tendon complex and muscle activities and performances during jumping. METHODS: Ten subjects completed 12 wk (4 d.wk(-1)) of a unilateral training program for plantar flexors. They performed plyometric training on one side (PT; hopping and drop jump using 40% of 1RM) and weight training on the other side (WT; 80% of 1RM). Tendon stiffness was measured using ultrasonography during isometric plantar flexion. Three kinds of unilateral jump heights using only ankle joint (squat jump: SJ; countermovement jump: CMJ; drop jump: DJ) on sledge apparatus were measured. During jumping, electromyographic activities were recorded from plantar flexors and tibial anterior muscle. Joint stiffness was calculated as the change in joint torque divided by the change in ankle angle during eccentric phase of DJ. RESULTS: Tendon stiffness increased significantly for WT, but not for PT. Conversely, joint stiffness increased significantly for PT, but not for WT. Whereas PT increased significantly jump heights of SJ, CMJ, and DJ, WT increased SJ only. The relative increases in jump heights were significantly greater for PT than for WT. However, there were no significant differences between PT and WT in the changes in the electromyographic activities of measured muscles during jumping. CONCLUSION: These results indicate that the jump performance gains after plyometric training are attributed to changes in the mechanical properties of muscle-tendon complex, rather than to the muscle activation strategies.     

Association between isometric muscle strength and gait joint kinetics in adolescents and young adults with cerebral palsy

The purpose of this study was to determine the association between isometric muscle strength of the lower limbs and gait joint kinetics in adolescents and young adults with cerebral palsy (CP). Twenty-five participants (11 males) with bilateral spastic CP, aged 14-22 years (mean: 18.9, sd: 2.0 yr) and Gross Motor Function Classification System (GMFCS) level II (n=19) and III (n=6) were tested. Hand held dynamometry was used to measure isometric strength (expressed in Nm/kg) of the hip, knee, and ankle muscles using standardized testing positions and procedures. 3D gait analysis was performed with a VICON system to calculate joint kinetics in the hip, knee and ankle during gait. Ankle peak moments exceeded by far the levels of isometric strength of the plantar flexors, while the knee and hip peak moments were just at or below maximal isometric strength of knee and hip muscles. Isometric muscle strength showed weak to moderate correlations with peak ankle and hip extension moment and power during walking. Despite considerable muscle weakness, joint moment curves were similar to norm values. Results suggest that passive stretch of the muscle-tendon complex of the triceps surae contributes to the ankle moment during walking and that muscle strength assessment may provide additional information to gait kinetics.     

Relationship between postural sway on an unstable platform and ankle plantar flexor force steadiness in community-dwelling older women

BackgroundForce steadiness is evaluated as force variability during constant force exertion around a target level. Ankle plantar flexor force steadiness is reported to be related to postural sway on an unstable platform in healthy young adults; however, this relationship in older adults is unclear.Research questionThis study aimed to investigate whether ankle plantar flexor force steadiness was related to postural sway on stable and unstable platforms in older adults.MethodsTwenty-six community-dwelling older women participated in this study (72 ± 6 years). Maximal isometric strength and force steadiness at 5%, 20 %, and 50 % of the maximal strength of ankle plantar flexion were assessed. Postural sway in the anteroposterior direction during bipedal standing was measured on stable and unstable platforms.ResultsThe results showed that force steadiness at any intensity level and maximal isometric strength were not related to postural sway on the stable platform. Force steadiness at 20 % of maximal strength alone was significantly correlated with postural sway on the unstable platform (ρ = 0.441, p < 0.05).SignificanceThese results indicate that the ability to control muscle force could be important for postural stability on an unstable platform in older adults.     

Fatigue and recovery at long and short muscle lengths after eccentric training

PURPOSE: To determine the effects of high-speed eccentric training of rat plantar flexor muscles on: 1) maximum (120 Hz) force at 90 degrees ankle position; 2) fatigue (40 concentric muscle actions, ROM 50 degrees) and recovery (6 concentric muscle actions) tested at short or long muscle lengths; and 3) low-frequency fatigue. METHODS: Training consisted of eccentric muscle actions from ankle positions of 140 degrees to 40 degrees (velocity approximately 400 degrees x s(-1)) followed by unresisted concentric muscle actions (5 x 10 repetitions, 5 d x wk(-1) for 6 wk). Fatigue was induced by concentric muscle actions with a rest of 12.5 s between muscle actions, and recovery consisted of equivalent concentric muscle actions performed every 5 min for 30 min. Low-frequency fatigue was measured 35 min after testing at 90 degrees ankle position by using the ratio of isometric force produced by 20- and 100-Hz stimulation frequencies. RESULTS: Eccentric training increased maximal isometric force per muscle weight by 22% whereas muscle weights were unchanged. In control muscles (C), isometric force immediately preceding each concentric muscle action decreased more at long lengths than at short lengths during the fatigue protocol; this length-dependent difference disappeared after 30 min of recovery. At short lengths, isometric force decreased less in trained muscles (T) (C: 78.4 +/- 3.6%; T: 59.6 +/- 4.4%) and recovered more during the following 30-min period (C: 84.7 +/- 2.5%; T: 95.4 +/- 2.8% of initial values). Changes in F20/F100 were smaller for trained muscles (C: 35.4 +/- 2.0%; T: 22.0 +/- 1.4%). CONCLUSIONS: High-speed eccentric training (5 d x wk(-1) for 6 wk) reduced fatigability and enhanced recovery mainly at long muscle lengths. It also reduced low-frequency fatigue, which may be attributed to alterations in intracellular calcium handling.     

Comparison of lower limb muscle strength between diabetic neuropathic and healthy subjects using OpenSim

Diabetes neuropathy and vasculopathy are the two major complications of diabetes mellitus, leading to diabetic foot disease, of which the worst consequences are plantar ulcers and amputations. Motor impairments like joint stiffness and loss of balance are distinctive effects of diabetes and they have been extensively explored. However, while altered muscle function has been also assessed through experimentally measured surface electromyography, little is known about muscle forces. The objective of this study was to estimate muscle forces in subjects with diabetes and to use these data to identify differences with respect to a population of healthy subjects matched for age and BMI. This was obtained by generating musculoskeletal models of 10 diabetic and 10 control subjects in OpenSim starting from experimentally recorded data. Dynamic simulations of motion were run and hence muscle forces calculated. Student T test (p < 0.05) was used to compare joints kinematics, kinetics and muscle forces between the two populations. Significant changes were observed between lower limb muscle forces and activation of diabetic and healthy subjects, as well as between joints kinematics and kinetics. In particular muscles related to foot movements proved to be stronger in the healthy population. The typical ankle rigidity of the diabetic population was confirmed by a lower range of motion registered at the ankle plantar/flexion angle associated with weaker dorsal-plantar flexor muscles. The information provided by this methodology can help planning specific training programs aiming at augmenting muscle strength and joints mobility, and they can also improve the evaluation of the potential benefits.     

Effect of resistance training on muscle fatigue and recovery in intact rats

PURPOSE: To examine the effect of resistance training on muscle fatigue from intermittent contractions and subsequent recovery in intact rats. METHODS: By using electrical stimulation, plantar flexor muscles were trained with eccentric and concentric contractions (5 x 10 repetitions, 5 d x wk(-1) for 6 wk) during ankle rotations. By using nerve stimulation, concentric contractions (40) imposed on isometric contractions (stimulation time, 1.9 s; rest period, 13.6 s; intermittent contractions) induced fatigue. During recovery, equivalent contractions were used every 5 min for 30 min. RESULTS: Training increased isometric forces (19% and 23% at ankle positions of 1.57 and 0.70 rad), but muscle weights were not changed. After training, smaller declines in isometric (control, 68.9+/-1.4%; trained, 58.8+/-2.9%) and average concentric force (control, 71.6+/-0.7%; trained, 65.5+/-2.8%) occurred from fatigue. Recovery for 5 min returned isometric and average concentric force to 61.7+/-2.2% and 65.1+/-2.5% of initial values for controls and 76.9+/-2.2% and 77.1+/-2.2% after training. After recovery for 30 min, these forces were 87.6+/-0.7% and 89.2+/-1.1% of initial values for controls and recovered almost completely (94.2+/-1.3% and 94.6+/-1.6%) in trained muscles. During fatigue, the decline in force during successive concentric contractions was larger after training (from 19.7+/-1.1% to 50.1+/-2.0%; controls, from 19.9+/-2.0% to 41.7+/-1.4%). Recovery of this decline in force was training-independent and complete within 5 min. CONCLUSIONS: Rat plantar flexor muscles adapt to 6 wk of 5 d x wk(-1) resistance training with: 1) increased isometric force, 2) smaller losses in isometric and average concentric force during fatigue, 3) larger force decline during concentric contractions during fatigue, and 4) improved recovery following fatigue. Different mechanisms might account for the recovery of the average concentric force and the decline in force during concentric contractions.