Loss of maximal explosive power of lower limbs after 2 weeks of disuse and incomplete recovery after retraining in older adults

Abstract

Key pointsr Disuse in older adults can critically decrease lower limb muscle power, leading to compromised mobility and overall quality of life.r We studied how muscle power and its determinants (muscle mass, single muscle fibre properties and motor control) adapted to 2 weeks of disuse and subsequent 2 weeks of physical training in young and older people.r Disuse decreased lower limb muscle power in both groups; however, different adaptations in single muscle fibre properties and co-contraction of leg muscles were observed between young and older individuals.r Six physical training sessions performed after disuse promoted the recovery of muscle mass and power. However, they were not sufficient to restore muscle power to pre-disuse values in older individuals, suggesting that further countermeasures are required to counteract the disuse-induced loss of muscle power in older adults.Enrico Rejc is presently Assistant Professor and Director of the Neuromuscular and Skeletal Research Core at the Kentucky Spinal Cord Injury Research Center, Department of Neurosurgery, University of Louisville, USA. Prior to taking this position, he was also involved in research activities at the University of Udine, University of California, Los Angeles, and Manchester Metropolitan University. He has studied the effects of disuse, ageing, spinal cord injury and physical exercise on the human neuromuscular system for about 10 years. His research is also focused on the recovery of motor function after severe spinal cord injury using spinal cord epidural stimulation and activity-based training. Stefano Lazzer is Professor and Director of the School of Sport and Exercise Sciences, Department of Medicine, University of Udine, Italy. He studies the physiology of muscle contraction, bioenergetics and cardio-respiratory adaptations to exercise on human health and performance. His current research programme is focused on the metabolic responses during exercise and the adaptation of humans disuse and training. Abstract Disuse-induced loss of muscle power can be detrimental in older individuals, seriously impairing functional capacity. In this study, we examined the changes in maximal explosive power (MEP) of lower limbs induced by a 14-day disuse (bed-rest, BR) and a subsequent 14-day retraining, to assess whether the impact of disuse was greater in older than in young men, and to analyse the causes of such adaptations. Sixteen older adults (Old: 55-65 years) and seven Young (18-30 years) individuals participated in this study. In a subgroup of eight Old subjects, countermeasures based on cognitive training and protein supplementation were applied. MEP was measured with an explosive ergometer, muscle mass was determined by magnetic resonance, motor control was studied by EMG, and single muscle fibres were analysed in vastus lateralis biopsy samples. MEP was ß33% lower in Old than in Young individuals, and remained significantly lower (−19%) when normalized by muscle volume. BR significantly affected MEP in Old (−15%) but not in Young. Retraini...

Postpolio syndrome and the late effects of poliomyelitis. Part 1. pathogenesis, biomechanical considerations, diagnosis, and investigations

“…The normal aging process also specifically involves the loss of motor neurons with advancing age, particularly over the age of 60 years . Physical inactivity and muscle disuse, which lead to deconditioning and muscle weakness, may also play roles; it has been demonstrated that 10 days of bed rest results in significant loss of whole‐body lean tissue, lower body lean tissue, and strength in otherwise healthy older individuals . Muscle disuse in older healthy adults can critically decrease lower limb muscle power leading to impaired functional capacity, compromised mobility, and overall decline in quality of life, and it has been suggested that a similar effect may occur in postpolio individuals .…”

“…[45][46][47] Muscle disuse in older healthy adults can critically decrease lower limb muscle power leading to impaired functional capacity, compromised mobility, and overall decline in quality of life, and it has been suggested that a similar effect may occur in postpolio individuals. 46,48 It has been postulated that these various factors, superimposed upon the polio-related motor neuron loss and compensatory motor unit changes, may be factors in the disturbance of the denervation/reinnervation equilibrium, contribute to the progressive loss of motor units, and be primary etiological factors in the development of PPS. 49 Another proposed theory in the pathogenesis of PPS is the persistence or reactivation of the poliovirus that results in the progressive motor neuron degeneration.…”

“…Physical inactivity and muscle disuse, which lead to deconditioning and muscle weakness, may also play roles; it has been demonstrated that 10 days of bed rest results in significant loss of whole‐body lean tissue, lower body lean tissue, and strength in otherwise healthy older individuals . Muscle disuse in older healthy adults can critically decrease lower limb muscle power leading to impaired functional capacity, compromised mobility, and overall decline in quality of life, and it has been suggested that a similar effect may occur in postpolio individuals . It has been postulated that these various factors, superimposed upon the polio‐related motor neuron loss and compensatory motor unit changes, may be factors in the disturbance of the denervation/reinnervation equilibrium, contribute to the progressive loss of motor units, and be primary etiological factors in the development of PPS …”

Tensiomyography detects early hallmarks of bed-rest-induced atrophy before changes in muscle architecture

“…Declines in muscle mass and function after such short periods are of high clinical relevance to most patients who are, on average, hospitalized for Ͻ7 days (15). The disuse-induced loss of muscle mass is particularly relevant for the elderly who show higher atrophy after 14-day bed rest and a much slower recovery or even complete lack of recovery for at least 14 days afterward (33,36). Therefore, there is a substantial need to develop methods to detect early stages of muscle atrophy-related processes.…”

Dietary Protein and Muscle in Aging People: The Potential Role of the Gut Microbiome

“…Age associated loss of muscle mass starts as early as age thirty, and is a gradual process [ 1 ]. Older people lose more skeletal muscle with bedrest and show an attenuated response to retraining after immobilisation, in comparison to younger individuals [ 2 , 3 , 4 ]. Sarcopenia is a geriatric syndrome defined as the age-related loss of skeletal mass and function, quantified by objective measures of muscle mass, strength, and physical function [ 5 ].…”