Effects of strength and endurance training on isometric muscle strength and walking speed in elderly women

The separate effects of 18 weeks of intensive strength and endurance training on isometric knee extension (KE) and flexion (KF) strength and walking speed were studied in 76-to 78-year-old women. Maximal voluntary isometric force for both KE and KF was measured in a sitting position on a custom-made dynamometer chair at a knee angle of 60° from full extension. Maximal walking speed was measured over a distance of 10 m. The endurance-trained women increased KE torque and KE torque/body mass after the first 9 weeks of training when compared with the controls. When comparing the baseline, 9 week and 18 week measurements within the groups separately, both the endurance- and strength-training groups increased KE torque, KE torque/body mass and walking speed. Individual changes in KE torque/body mass before and after 18 weeks of training averaged 19.1% in the strength group, 30.9% in the endurance group and 2.0% in the controls. This study indicates that in elderly women the effects of physical training on muscle strength and walking speed occur after endurance as well as strength training. The considerable interindividual variation in change of muscle performance is also worth noticing.     

Specificity of velocity in strength training

Summary Twenty-one male volunteers (ages 23–25 years) were tested pre- and post training for maximal knee extension power at five specific speeds (1.05, 2.09, 3.14, 4.19, and 5.24 rad·s⁻¹) with an isokinetic dynamometer. Subjects were assigned randomly to one of three experimental groups; group S, training at 1.05 rad·s⁻¹ (n=8), group I, training at 3.14 rad·s⁻¹ (n=8) or group F, training at 5.24 rad·s⁻¹ (n=5). Subjects trained the knee extensors by performing 10 maximal voluntary efforts in group S, 30 in group I and 50 in group F six times a week for 8 weeks. Though group S showed significant increases in power at all test speeds, the percent increment decreased with test speed from 24.8% at 1.05 rad·s⁻¹ to 8.6% at 5.24 rad·s⁻¹. Group I showed almost similar increment in power (18.5–22.4 at all test speeds except at 2.09 rad·s⁻¹ (15.4%). On the other hand, group F enhanced power only at faster test speeds (23.9% at 4.19 rad·s⁻¹ and 22.8% at 5.24 rad·s⁻¹).     

Effects of isokinetic training of the knee extensors on isometric strength and peak power output during cycling

Summary Isokinetic training of right and left quadriceps femoris was undertaken three times per week for 16 weeks. One group of subjects (n=13) trained at an angular velocity of 4.19 rad·s^–1 and a second group (n=10) at 1.05 rad·s^–1. A control group (n=10) performed no training. Maximal voluntary contraction (MVC) of the quadriceps, and peak pedal velocity (_p,peak) and peak power output (W _peak) during all-out cycling (against loads equivalent to 9, 10, 11, 12, 13 and 14% MVC) were assessed before and after training. The two training groups did not differ significantly from each other in their training response to any of the performance variables (P>0.05). No significant difference in MVC was observed for any group after the 16-week period (P=0.167). The post-training increases in averageW _peak (7%) and _p,peak (6%) during the cycle tests were each significantly different from the control group response (P=0.018 andP=0.008, respectively). It is concluded that 16 weeks of isokinetic strength training of the knee extensors is able to significantly improve _p,peak andW _peak during sprint cycling, an activity which demands considerable involvement of the trained muscle group but with its own distinct pattern of coordination.     

The impact of joint angle and movement velocity on sex differences in the functional hamstring/quadriceps ratio

Background

Females are two to eight times more likely to suffer a non-contact injury compared with males thus the purpose of this study was to explore the influence of joint angle and movement velocity on sex differences in the functional hamstring to quadriceps ratio (H/Q_FUNC).

踝关节等速肌力训练对老年脑卒中患者平衡功能的影响

目的　探讨应用等速肌力训练加强踝关节屈伸肌群的肌力,对老年脑卒中患者平衡功能的影响。 方法　选取40例老年脑卒中患者随机分为对照组（n=20）、治疗组（n=20）,对照组接受常规康复治疗,治疗组在对照组基础上,增加针对踝关节背伸与跖屈肌群的等速肌力训练。2组患者治疗前和治疗3周后均进行Berg平衡量表（Berg balance scale, BBS）;“起立-走”计时测试（Timed up and go test, TUGT）;以及ProKin平衡仪的评估,参数包括Y-COP标准差、运动轨迹长度、运动轨迹面积、踝关节背伸与跖屈肌群的等速峰力矩等平衡功能相关指标的测量。 结果　2组患者经过平衡训练后,平衡功能的各项指标均较治疗前有改善(P<0.05）;治疗组患者治疗后平衡功能与对照组比较,各项评估指标均优于对照组(P<0.05）。 结论　踝关节等速肌力训练,可以明显改善老年脑卒中患者踝关节背伸与跖屈肌群的肌力及平衡功能。     

Effects of velocity of isokinetic training on strength,power, and quadriceps muscle fibre characteristics

Summary Twenty young men trained the right knee extensors and flexors on an isokinetic dynamometer three times weekly over a 10-week period. During each session, 10 men in the slow training group completed three sets of 8 maximal contractions at a rate of 1.05 rad s^–1, whereas the other 10, the fast group, completed three sets of 20 contractions at a rate of 4.19 rad s^–1. Subjects were pre- and post-tested for peak torque and power on an isokinetic dynamometer at 1.05, 3.14, and 4.19 rad s^–1. Proportions of muscle fibre-types and fibre cross-sectional areas were determined from biopsy specimens taken before and after training from the right vastus lateralis. When testing was conducted at 1.05 rad s^–1, the slow group improved (P<0.05) peak torque by 24.5 N m (8.5%), but no change was noted for the fast group. Power increased (P< 0.05) by 32.7 W (13.6%) in the slow group and 5.5 W (2.5%) in the fast. At 3.14 rad s^–1, both groups increased (P<0.05) peak torque and power. At 4.19 rad s^–1, the fast group increased (P<0.05) peak torque by 30.0 N m (19.7%), whereas no training effect was observed in the slow group. There was no significant change in power in either group at 4.19 rad s^–1, No significant changes were observed over the 10-week training period in percentages of type I, IIa and IIb fibres, but both groups showed significant increases (P<0.05) in type I and IIa fibre areas. No differences were noted between groups, and no hypertrophy of type IIb fibres was observed.     

抗阻训练对绝经后女性身体成分、膝关节肌肉力量及动态平衡能力的影响

目的：探讨抗阻训练对绝经后女性身体成分、膝关节屈伸肌力及动态平衡能力的影响。方法：将25 名绝 经女性随机分为抗阻训练组和对照组,抗阻训练前后测试绝经后女性身体成分（ 体质量、体脂肪量、肌肉量、左 右下肢肌肉量）,左、右膝关节屈、伸肌力及动态平衡能力。结果：12 周抗阻训练可使绝经后女性体脂肪量显著 下降,左右下肢肌肉量及全身肌肉量均显著增加,而体质量在抗阻训练前后无显著差异;此外,12 周抗阻训练可 使绝经后女性左、右膝关节屈、伸肌肌力显著增加,闭眼状态下总体稳定指数、前后方向稳定指数及左右方向稳 定指数显著下降。结论：12 周抗阻训练可显著降低绝经后女性身体脂肪量、增加下肢肌肉量及膝关节肌肉力量, 改善动态平衡能力,对于预防绝经后女性跌倒及提高绝经后女性生存质量有重要意义。     

Maximal strength and power characteristics in isometric and dynamic actions of the upper and lower extremities in middle-aged and older men

Muscle cross-sectional area of the quadriceps femoris (CSA_QF), maximal isometric strength (handgrip test and unilateral knee extension/flexion), the shape of isometric force–time curves, and power–load curves during concentric and stretch–shortening cycle (SSC) actions with loads ranging from 15 to 70% of one repetition maximum half-squat (1RM_HS) and bench-press (1RM_BP) were examined in 26 middle-aged men in the 40-year-old (M40) (mean age 42, range 35–46) and 21 elderly men in the 65-year-old age group (M65) (mean age 65, range 60–74). Maximal bilateral concentric (1RM_HS and 1RM_BP), unilateral knee extension (isometric; MIF_KE and concentric; 1RM_KE) strength and muscle CSA in M65 were lower (P < 0.001) than in M40. The individual values of the CSA_QF correlated with the individual values of maximal concentric 1RM_HS, 1RM_KE and MIF_KE in M65, while the corresponding correlations were lower in M40. The maximal MIF_KE value per CSA of 4.54 ± 0.7 N m cm^–2 in M40 was greater (P < 0.05–0.01) than that of 4.02 ± 0.7 N m cm^–2 recorded in M65. The maximal rate of force development of the knee extensors and flexors in M65 was lower (P < 0.01–0.001) and the heights in squat and counter-movement jumps as much as 27–29% lower (P < 0.001) than those recorded in M40. M65 showed lower (P < 0.001) concentric power values for both upper and lower extremity performances than those recorded for M40. Maximal power output was maximized at the 30–45% loads for the upper extremity and at the 60–70% loads for the lower extremity extensors in both age groups. Muscle activation of the antagonists was significantly higher (P < 0.01–0.001) during the isometric and dynamic knee extension actions in M65 than in M40. The present results support a general concept that parallel declines in muscle mass and maximal strength take place with increasing age, although loss of strength may vary in both lower and upper extremity muscles in relation to the type of action and that ageing may also lead to a decrease in voluntary neural drive to the muscles. Explosive strength and power seem to decrease with increasing age even more than maximal isometric strength in both actions but power was maximized at the 30–45% loads for the upper and at the 60–70% loads for the lower extremity action in both age groups. High antagonist muscle activity may limit the full movement efficiency depending on the type of muscle action, testing conditions and the velocity and/or the time duration of the action, especially in the elderly.     

Effects of eccentric strength training on biceps femoris muscle architecture and knee joint range of movement

The aim was to determine whether eccentric strengthening changed the muscle architecture of human biceps femoris and consequently, knee range of motion. Twenty-two subjects were randomly assigned to control and experimental groups. The experimental group completed an eccentric strengthening programme for 8 weeks. Outcome measures included hamstring muscle strength (one repetition maximum), the passive knee extension test (PKE) (knee joint angle at which the onset of passive tension occurs), fascicle length (FL) and pennation angle (PA). One repetition maximum increased by 34% (P < 0.01), the PKE test revealed a 5% increase in joint range of motion (P = 0.01), FL increased by 34% (P = 0.01) and PA did not change (P = 0.38). This is the first report of an increase in FL in the biceps femoris following eccentric resistance training. In addition, the results might imply that this fascicle lengthening could lead to an increase in the range of motion of the knee. Clinical implications for rehabilitation and injury prevention are discussed.     

Comparison of force–velocity relationships of vastus lateralis muscle in isokinetic and in stretch‐shortening cycle exercises

Aim: This study investigated the force–velocity characteristics of the vastus lateralis (VL) muscle fascicle and muscle–tendon unit (MTU) in isolated lengthening and shortening actions, and during natural movement. Methods: Four subjects performed maximal eccentric and concentric knee extensions (60, 120 and 180° s^?1). Unilateral counter movement jumps and drop jumps in the sledge apparatus served as natural movements. Vastus lateralis fascicle lengths were determined from ultrasonography. In vivo patellar tendon forces (PTF) were measured with an optic fibre technique. Patellar tendon force was derived to VL force according to the cross‐sectional area of the muscle. Force in the direction of fascicle was calculated by dividing the VL force value by cosine of the fascicle angle. Force–velocity curves were constructed using angle specific values from isokinetic knee extensions (classical curve) and using instantaneous values from jumping exercises. Results: In the fascicle level, we did not find an enhanced muscle force in the jumping performances as compared with the classical force–velocity curve. In the muscle–tendon level, the instantaneous force at high muscle–tendon shortening speeds exceeded that extrapolated according to Hill's equation. Conclusion: This difference between fascicle and muscle–tendon behaviour suggests that the neural input in fast stretch‐shortening cycle exercises minimizes the length changes in muscle fascicle and enables storage and recoil of energy from elastic components that contributes to the enhanced mechanical output of the MTU during the push‐off phase.     

Enzyme adaptations of human skeletal muscle during bicycle short-sprint training and detraining

The effect of sprint training and detraining on supramaximal performances was studied in relation to muscle enzyme adaptations in eight students trained four times a week for 9 weeks on a cycle ergometer. The subjects were tested for peak oxygen uptake (V˙O_{2 peak}), maximal aerobic power (MAP) and maximal short-term power output (W˙_max) before and after training and after 7 weeks of detraining. During these periods, biopsies were taken from vastus lateralis muscle for the determination of creatine kinase (CK), adenylate kinase (AK), glycogen phosphorylase (PHOS), hexokinase (HK), phosphofructokinase (PFK), lactate dehydrogenase (LDH) and its isozymes, 3-hydroxy-acyl-CoA dehydrogenase (HAD) and citrate synthase (CS) activities. Training induced large improvements in W˙_max (28%) with slight increases (3%) in V˙O_{2 peak}} (P < 0.10). This was associated with a greater glycolytic potential as shown by higher activities for PHOS (9%), PFK (17%) and LDH (31%) after training, without changes in CK and oxidative markers (CS and HAD). Detraining induced significant decreases in V˙O_{2 peak} (4%), MAP (5%) and oxidative markers (10–16%), while W˙_max and the anaerobic potential were maintained at a high level. This suggests a high level in supramaximal power output as a result of a muscle glycogenolytic and glycolytic adaptation. A long interruption in training has negligible effects on short-sprint ability and muscle anaerobic potential. On the other hand, a persistent training stimulus is required to maintain high aerobic capacity and muscle oxidative potential. This may contribute to a rapid return to competitive fitness for sprinters and power athletes.     

最佳功率负荷下不同力量训练手段骨骼肌输出功率的确定及特征

背景:在最佳功率负荷下进行力量训练能实现骨骼肌输出功率的最大化,骨骼肌输出功率的增大能提高运动员的运动表现和大众的健康水平,备受国内外学者和体能教练的青睐。目的:确定不同力量训练手段最佳功率负荷,分析不同力量训练手段最佳功率负荷输出功率特征。方法:选择北京体育大学男性大学生运动员27名,进行半蹲起和卧推抛最大力量测试,利用九轴传感器测试受试者在10%,30%,50%,70%和90%最大力量负荷下的输出功率。结果与结论:①半蹲起的最佳功率负荷为70%最大力量,其平均输出功率和最大输出功率均显著高于10%,30%,50%最大力量(P<0.01);半蹲起输出功率与最大速度呈高度相关(r=0.84-0.87,P<0.01),与平均速度和平均力呈中度相关(r=0.50-0.68,P<0.01),与最大力量呈低度相关(r=0.40,P<0.05);②卧推抛的最佳功率负荷为70%最大力量,其平均输出功率显著高于10%最大力量(P<0.01)、30%最大力量(P<0.05)和90%最大力量(P<0.01);卧推抛输出功率与平均速度、最大速度、最大力呈高度相关(r=0.70-0.84,P<0.01),与平均力和最大力量呈中度相关(r=0.57-0.70,P<0.01),与体质量和训练年限呈低度相关(r=0.40-0.46,P<0.05);③结果表明,大学生运动员半蹲起和卧推抛的最佳功率负荷均值为70%最大力量,由于个体生理学和训练学差异性,骨骼肌精确的最佳功率负荷仍需进一步测量;提高大学生运动员骨骼肌的最大输出功率时,发展骨骼肌收缩速度优先于发展骨骼肌收缩力。     

Assessment of human knee extensor muscles stress from in vivo physiological cross-sectional area and strength measurements

Summary The physiological cross-sectional areas (CSAp) of the vastus lateralis (VL), vastus intermedius (VI), vastus medialis (VM) and rectus femoris (RF) were obtained, in vivo, from the reconstructed muscle volumes, angles of pennation and distance between tendons of six healthy male volunteers by nuclear magnetic resonance imaging (MRI). In all subjects, the isometric maximum voluntary contraction strength (MVC) was measured at the optimum angle at which peak force occurred. The MVC developed at the ankle was 746.0 (SD 141.8) N and its tendon component (F _t) given by a mechanical advantage of 0.117 (SD 0.010), was 6.367 (SD 1.113) kN. To calculate the force acting along the fibres (F _f) of each muscle, F _t was divided by the cosine of the angle of pennation and multiplied for (CSAp · CSAp^–1), where CSAp was the sum of CSAp of the four muscles. The resulting F _f values of VL, VI, VM and RF were: 1.452 (SD 0.531) kN, 1.997 (SD 0.187) kN, 1.914 (SD 0.827) kN, and 1.601 (SD 0.306) kN, respectively. The stress of each muscle was obtained by dividing these forces for the respective CSAp which was: 6.24 × 10^–3 (SD 2.54 × 10^–3) m² for VL, 8.35 × 10^–3 (SD 1.17 × 10^–3) m² for VI, 6.80 × 10^–3 (SD 2.66 × 10^–3) m² for VM and 6.62 × 10^–3 (SD 1.21 × 10^–3) m² for RE The mean value of stress of VL, VI, VM and RF was 250 (SD 19) kN m²; this value is in good agreement with data on animal muscle and those on human parallel-fibred muscle.     

Shortening velocity and force/pCa relationship in skinned crab muscle fibres of different types

Single fibres of three different types, which had been characterized histochemically with regard to differences in myofibrillar adenosine triphosphatase (ATPase) activity and its pH stability, were microdissected from freeze dried preparations of the closer muscle in walking legs of the crab Eriphia spinifrons. Shortening velocities were determined in slack tests and under constant load conditions in maximally Ca²⁺-activated skinned muscle fibres. Force/pCa relationships were also measured for the different types of fibres. Compared with data on vertebrate muscles, all crab muscle fibres required large length changes to reach zero force and showed low Ca²⁺ sensitivity for isometric force generation. The length/time relationship obtained from slack tests had a biphasic course. Maximal velocity of filament sliding differed in the three types of fibres investigated. The filament sliding of type IV fibres was about 3 times faster than that of type I fibres. The values obtained for type II fibres ranged in between. These data are positively correlated with myofibrillar ATPase activity determined histochemically. Ca²⁺ sensitivity of force generation was lowest in the fast type IV fibres. It was high in the slow type I and the faster contracting type II fibres. Ca²⁺ sensitivity in crab muscle seems not to be correlated with speed of shortening.     

Exploration of myostatin polymorphisms and the angiotensin-converting enzyme insertion/deletion genotype in responses of human muscle to strength training

This study explores the associations between polymorphisms in two candidate genes—myostatin gene (MSTN or GDF8) and angiotensin-converting enzyme (ACE) gene—with interindividual differences in human muscle mass and strength responses to strength training. The MSTN AluI A55T (exon 1), BanII K153R, TaqI E164 K and BstNI P198A (all in exon 2) markers and the ACE insertion (I)/deletion (D) polymorphism were typed in 57 males [22.4 (3.7) years] who participated in a 10-week, high-resistance training program for the elbow flexors. Maximal strength, and maximal isometric and concentric elbow flexor torques were measured at baseline and after training. Information on muscle cross-sectional area of the upper arm was obtained by computer tomography scans. Only one individual was heterozygous for the MSTN BanII K153R variant. No allelic variant was detected at the other MSTN sites in this population. For the ACE I/D polymorphism, no evidence was found for an association of the D or I allele with baseline strength, isometric and concentric torque or arm muscle cross-sectional area [analysis of covariance (ANCOVA) 0.25<P<0.97]. Responses to the strength-training program were not associated with the ACE I/D genotype (ANCOVA 0.057<P<0.70). Borderline significance was found for larger strength gains in dynamic flexion torques for I/I genotypes. This study therefore does not support the hypothesis that an increased muscle fiber hypertrophic effect of strength training is present in D-allele carriers.     

The high-force region of the force-velocity relation in frog skinned muscle fibres

The force-velocity relation has been studied during calcium-induced contracture of chemically skinned fibres from the semitendinosus muscle of Rana temporaria with special interest focused on the high-load region. The force-velocity curve was hyperbolic at low and intermediate loads but departed below the hyperbola as the load exceeded about 80% of the isometric force (P_o). The force intercept (P*_o) of the hyperbola derived from force-velocity data truncated at 0.78 P_o was higher than P_o (P*_o /P_o = 1.14±0.04). At submaximum Ca²⁺ concentration, where the isometric force of the fibre was 65–75% of the maximum value, the force-velocity data still departed below the hyperbola at high loads (P_o /P_o = 1.09±0.04). The departure of the force-velocity data from the hyperbola at high force was also found at high ionic strength (250 mM), but not at low ionic strength (150 mM) (P_o /P_o = 1.09±0.03 and 0.98±0.03, respectively). The force-velocity relations derived under different experimental conditions could be fitted well by a modified version of Hill's (1938) hyperbolic equation (Edman 1988) using similar numerical values of k₁ and k₂ in the latter equation. The results indicate that the force-velocity relation in skinned muscle fibres is biphasic, and that the two curvatures, as in intact muscle fibres, are closely related to one another. Furthermore the evidence supports the hypothesis that the altered shape of the force-velocity relation at high loads is not related to the force level per se but rather to the speed of shortening of the contractile system (Edman 1992).     

Serial effects of high-resistance and prolonged endurance training on Na+–K+ pump concentration and enzymatic activities in human vastus lateralis

The purpose of this study was to compare two contrasting training models, namely high-resistance training and prolonged submaximal training on the expression of Na⁺–K+ ATPase and changes in the potential of pathways involved in energy production in human vastus lateralis. The high-resistance training group (VO _2peak = 45.3 ± 1.9 mL kg^?1 min^?1, mean ± SE, n = 9) performed three sets of six to eight repetitions maximal, each of squats, leg presses and leg extensions, three times per week for 12 weeks, while the prolonged submaximal training group (VO _2peak = 44.4 ± 6.6 mL kg^?1 min^?1, n = 7) cycled 5–6 times per week for 2 h day^?1 at 68% VO _2peak for 11 weeks. In the HRT group, Na⁺–K⁺ ATPase (pmol g^?1 wet wt), measured with the ³H-ouabain binding technique, showed no change from 0 (289 ± 22) to 4 weeks (283 ± 15), increased (P < 0.05) by 16% at 7 weeks and remained stable until 12 weeks (319 ± 19). For prolonged submaximal training, a 22% increase (P < 0.05) was observed from 0 (278 ± 31) until 3 weeks (339 ± 29) with no further changes observed at either 9 weeks (345 ± 25) or 11 weeks (359 ± 34). In contrast to high-resistance training, where a 15% increase (P < 0.05) was observed, only in the maximal activity of phosphorylase, prolonged submaximal training resulted in increases in malate dehydrogenase, β-hydroxyl-CoA dehydrogenase, hexokinase and phosphofructokinase. In contrast to high-resistance training which failed to result in an increase in VO _2peak, prolonged submaximal training increased VO _2peak by ≈15%. Only for prolonged exercise training was a relationship observed for VO _2peak and Na⁺–K⁺-ATPase (r = 0.59; P < 0.05). Correlations between VO _2peak and mitochondrial enzyme activities were not significant (P > 0.05) for either training programme. It is concluded that although both training programmes stimulate an up-regulation in Na⁺–K⁺ ATPase concentration, only the prolonged submaximal training programme enhances the potential for β-oxidation, oxidative phosphorylation and glucose phosphorylation.