Improvement in muscle strength with low‐load isotonic training depends on fascicle length but not joint angle

Abstract

Introduction: In this study we investigate whether low-load isotonic training will elicit greater improvement in muscle strength at the same fascicle length, rather than at the same joint angle. Methods: Sixteen healthy men (24.1 6 2.5 years of age) were randomly divided into intervention and control groups. Pre-and posttraining maximum isometric and isokinetic strengths and fascicle lengths of the medial gastrocnemius muscle were measured. Isotonic resistance training at 15 8 to 30 8 ankle plantarflexion at low intensity was conducted for 4 weeks. Results: The maximum isometric and isokinetic strength of the intervention group increased significantly only at 15 8 dorsiflexion and 8 8 to 12 8 dorsiflexion. Fascicle length during maximum voluntary contraction at 15 8 dorsiflexion to 0 8 was similar to fascicle length under training conditions. Discussion: It is possible that the improvement in muscle strength with low-load training depends on fascicle length rather than joint angle. 57: 83-89, 2018 Muscle strength is known to specifically improve at the applied angle of training. In isometric training, Kitai and Sale 1 reported that ankle plantarflexion training using maximum voluntary isometric contraction at an ankle angle of 0 8 (i.e., 90 8 angle between the tibia and the sole of the foot) produces an improvement in maximum isometric strength at an ankle position of only around 0 8 (between -5 8 and 5 8). These results demonstrate the so-called joint angle specificity on training effect. Muscle Nerve1 Moreover, it was reported that muscle strength specifically improves at the training angle used during not only isometric training but also isotonic and isokinetic training. Graves et al.2 and Barak et al., 3 respectively, examined the effect of isotonic and isokinetic high-load training of knee extension, and reported that the improvement in maximum isometric strength occurred at the training angle. On the other hand, some reports have demonstrated that an improvement in maximum muscle strength can be obtained over a wide range of joint angles around the training angle during isometric training 4-7 or eccentric isokinetic training.3 Thus, because a consensus view regarding joint angle specificity has yet to be achieved, further research and investigation are required.In general, it has been stated that a high load of more than 60% of maximum voluntary contraction is needed to gain an improvement in strength during resistance training.8 Therefore, all previous studies investigating the joint angle specificity of the training effect used a high load of more than 70% maximum voluntary isometric contraction or 60% 1 repetition maximum (1RM). However, our recent study 9 showed that isometric training with a low-intensity 30% maximum voluntary contraction was effective for improving the muscle strength at a different joint angle from the training angle. Our findings suggest that the effects of lowintensity training depend on not the joint angle specificity but rather on the fascicle length. The fascicle l...

Investigation of joint angle specificity in low-load hip abductor isometric training: a randomized controlled trial

“…The results of the present study did not follow the principle of specificity of joint angle, which was proposed by Kitai and Sale 5) and widely accepted [10][11][12] . On the other hand, the results supported the previous studies 7,8) , which reported that the MVC was improved more at an agonist muscle lengthened position than at the same position using training.…”

“…Kitai and Sale (1989) 5) reported that ankle plantarflexion training with a high load improved in the MVC at an ankle position only used during training. The previous study addressed this issue and found that low-load training at the agonist muscle in the shortened position improved the muscle strength only at a more lengthened (dorsiflexion) position than the position used during training in healthy young men 7,8) . Regarding the results, the authors also reported that the fascicle length during the training position, measured using ultrasound, was similar to the fascicle length during maximum voluntary contraction (MVC) at the angle that was obtained during improvements in MVC.…”

Differential changes in muscle architecture and neuromuscular fatigability induced by isometric resistance training at short and long muscle-tendon unit lengths

“…The data were nonnormally distributed and, therefore, log-transformed when analyzed and are presented as means Ϯ SD of raw data. no change (51,64,69,72) or only increases in FL (73) or PA (27,30,60). Based on previous studies (49,74), a greater FL increase induced by training is suggested to occur when training is performed at long MTU lengths due to a longer muscle stretch.…”

Benefits and Mechanisms of Exercise Training for Knee Osteoarthritis

“…Furthermore, a clinical trial of 61 patients with KOA showed that isotonic exercise can alleviate pain, stiffness, and improve knee joint function effectively, but it cannot increase quadriceps strength significantly ( Malas et al, 2013 ). In addition, Tanaka et al (2018) found that the muscle strength of patients with KOA could be effectively improved through low-load isotonic resistance exercise. Moreover, isotonic-centripetal exercise and isotonic-eccentric exercise has the same effect on increasing knee extension and knee flexion muscle strength, as well as relieving pain in patients with KOA ( Vincent et al, 2019 ).…”