Motor development
Ajay Sharma, Helen Cockerill, Lucy Sanctuary in Mary Sheridan's From Birth to Five Years, 2021
To walk, infants have to achieve dynamic balance as their bodies become less stable because of the smaller base on their feet and a higher centre of gravity. They also require sufficient muscle power, particularly in their extensor muscles, to balance the pull of the flexors and a change in the leg muscle activation from simultaneous co-activation of antagonistic muscles to reciprocal activation. When infants have sufficient strength to hold part of their body weight on one leg, they begin to move sideways, holding on to furniture, lifting the legs and arms one at a time. Next, they move forwards, with parents holding their hands, their bodies tilted 45° forward or backwards.
Osteoporotic thoracolumbar fractures
Peter V. Giannoudis, Thomas A. Einhorn in Surgical and Medical Treatment of Osteoporosis, 2020
Pain from vertebral fragility fractures can eventually lead to abnormal flexion of the spine to compensate for the discomfort. The overuse of spinal flexors will further aggravate the kyphotic spine. This overall imbalance between the use of back extensors and flexors will worsen the pain already present from the bony injury, subsequently leading to chronic pain. The degree of kyphosis has also been associated with increasing risk of vertebral fractures (90). Therefore, exercise programs focused on strengthening the spinal extensor muscles and correcting posture with the aim of reducing the degree of kyphosis to relieve pressure on the anterior aspect of the vertebral body has been recommended (77). The extensor muscles are considered the main supportive muscles of the spine, and in an erect posture, they resist the effects of gravity (77). A study comparing participants allocated to spinal extension, flexion, or extension and flexion programs reported statistically significant less vertebral fractures in the spinal extension group, where the focus is on strengthening the spinal erector muscles (91). Therefore, rehabilitation exercise programs for vertebral fragility fractures have incorporated this into their prescribed programs.
Modeling and simulation of tissue load in the human spine
Youlian Hong, Roger Bartlett in Routledge Handbook of Biomechanics and Human Movement Science, 2008
The effect of changes in passive properties of muscles and ligamentous spine on the results in general and the FRP in particular is found to be substantial. A decrease in passive contribution of extensor muscles (case with +5 per cent) (Figure 3.6) markedly increased activity in global extensor muscles and diminished that in abdominal muscles at larger flexion angles. A reverse trend was computed when the passive contribution was increased resulting in an earlier and greater activity in abdominal muscles but flexion relaxation in extensor muscles. Similar effects were also predicted as the bending rigidity of the ligamentous spine was altered (Figure 3.7). A decrease in passive stiffness due to an injury or joint relaxation could delay flexion relaxation in extensor muscles. The abdominal muscles are also affected by such changes.
Flexibility and strength training in asthma: A pilot study
Published in Journal of Asthma, 2018
Sara Olenich, Graeme Waterworth, Gary J. Badger, Bruce Levy, Elliot Israel, Helene M. Langevin
So far, current physical therapy practice and research have given little attention to manual therapies applied to the chest wall and upper extremities. Resistance Flexibility and Strength Training (RFST) is a nonconventional physical technique specifically aimed at correcting postural misalignment by applying resistive force while eccentrically contracting muscles to stretch dense fascia and scar tissue (26, 27). Thus, the patient performs an eccentric contraction of extensor muscles when the joint is flexed or of flexor muscles when the joint is extended. In this relatively simple technique, the combined externally applied torque exerted by the practitioner and the eccentric contraction performed by the patient act in concert to stretch the connective tissues, both within and surrounding the muscle. In the upper body, this technique uses the arm as a lever to stretch the muscles and connective tissues of the chest wall.
The effect of Knee-Ankle-Foot orthosis stiffness on the parameters of walking
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2018
Sayed Mohammad Ali Abtahi, Nima Jamshidi, Aram Ghaziasgar
The motor units generate force during walking, and the reduction of these units results in muscle weakness (Whittle 2014). This muscle weakness usually occurs in the ankle plantar flexor and knee flection muscles and it is representated in ground reaction force parameters (Jamshidi et al. 2010 and Jamshidi et al. 2009b). The activity of extensor muscles improves the stability of the body. This hierarchy begins with hamstrings and quadriceps activity to prepare limb in the swing phase to stand. When transferring the body weight on the foot rapidly, hip extensor and knee extensor muscles (quadriceps) increase knee and hip flexion stability; at the same time, the hip abductors support the pelvis. Since the body weight is passed over the foot, ankle plantar flexor controls the tibia and increases the hip and knee extensors stability indirectly (Ayyappa 1997).
Effect of hand postures and object properties on forearm muscle activities using surface electromyography
Published in International Journal of Occupational Safety and Ergonomics, 2020
Kyung-Sun Lee, Myung-Chul Jung
The contributions of individual forearm muscles to the muscle activity varied. The EPL and FPL muscles, which are involved with thumb functions, had the largest muscle activities, followed by the extension of the metacarpophalangeal joint, which is related to the ED for all four fingers, and the extension of the wrist in the ulnar direction, which is related to the ECU. In addition, the extensor muscle group showed higher muscle activity than the flexor muscle group. Similar to the study by Ayoub and Presti [15], this study found that the extensor muscles were activated to a greater extent than the flexor muscles when participants held an object weighing less than 2000 g. All of the extensor and flexor muscles must be activated to hold an object. In particular, the wrist extensors have to be activated to counteract the wrist flexor torque caused by the finger flexor tendons [40].