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Clinical Rehabilitation Technologies for Force-Control–Based Exoskeleton Robot
Published in Yuehong Yin, Biomechanical Principles on Force Generation and Control of Skeletal Muscle and their Applications in Robotic Exoskeleton, 2020
Isometric contraction training: While doing isometric contraction training, the exoskeleton’s joint angle is fixed. The gasbag is bound with human leg, and human joints are fixed. When the training starts, set the hip joint and knee joint of exoskeleton as 30° and 45° so that human legs are fixed. Then, the gasbag is charged, and F/E of calf is repeated to train the thigh muscles. In this process, the gasbag pressure and the EMG signal of each muscle are recorded, as illustrated in Figure 5.24. Referring to the figure, a group of antagonistic muscles, including the quadriceps femoris, biceps femoris, semitendinosus, and semimembranosus, are responsible for the extension and flexion of knee joint, respectively. When human calf extends forward, the EMG signal of quadriceps femoris is stronger. When calf flexes backward, the EMG signals of biceps femoris, semitendinosus, and semimembranosus are stronger. The muscle force can be calculated by force models to represent the training efficacy, as illustrated in Figure 5.25.
Effect of active resisted 30 m sprints upon step and joint kinematics and muscle activity in experienced male and female sprinters
Published in Journal of Sports Sciences, 2021
With increasing load, step and joint kinematics changed, while maximal muscle activation did not show much change with increasing load. So did maximal hamstring and calf muscle activity decrease, while maximal rectus femoris activity increased when load increased. However, this was only found significantly in women. An explanation for the decrease in hamstring activity is due to the lower maximal hip and knee extension with increasing loads. The biceps femoris and semitendinosus are mostly active during the late swing phase in which knee extension occurs (Higashihara et al., 2010; Kuitunen et al., 2002; Yu et al., 2008). These two muscles work as antagonists of the quadriceps and their role is to control knee extension during the late swing phase to avoid too much extension and to create a knee flexion moment (Higashihara et al., 2010). When the maximal knee extension decreased with increasing loads it is expected that hamstrings activation also would decrease. This was in accordance with the findings of Slawinski et al. (2008) who found that the hamstrings activation was lower when sprinting on an inclined surface compared to flat surface. When sprinting on an inclined surface the maximal knee extension velocity is less, which asks less activation of the hamstrings.
The effect of a passive trunk exoskeleton on metabolic costs during lifting and walking
Published in Ergonomics, 2019
S. J. Baltrusch, J. H. van Dieën, S. M. Bruijn, A. S. Koopman, C. A. M. van Bennekom, H. Houdijk
Muscle activity was recorded using surface Electromyography (Cometa Srl, Milan, Italy, Bandwith: 100 Hz, Input impedance: 20MOhm, Sampling Frequency: 2000 Hz). Surface electrodes were placed at 7 bilateral sites on the skin after abrasion and cleaning with alcohol (Ag-AgCl electrodes†; interelectrode distance, 20 mm). The recording sites were: m. longissimus thoracis (LT) at the T9 level (4 cm lateral), m. iliocostalis lumborum (IL) at the L2 level (6 cm lateral), m. longissimus lumborum (LL) at the L3 level (3 cm lateral), m. external oblique muscles (EO) about 15 cm above the SIAS, m. rectus abdominis (RA), 3 cm lateral from the umbilicus, m. vastus medialis (VM) and m. biceps femoris (BF).