Muscle Function: Effects of Aging

 

Original Editor - Wendy Walker

Top Contributors - Wendy Walker, Lucinda hampton, Andeela Hafeez, Kim Jackson, Vidya Acharya, Tony Lowe, Uchechukwu Chukwuemeka, Tarina van der Stockt, WikiSysop, Simisola Ajeyalemi, Rucha Gadgil, Amrita Patro, Lauren Lopez, Admin, Aminat Abolade, Evan Thomas, Lizzie Cotton and Claire Knott  

Introduction

As we age our muscles undergo progressive changes, primarily involving loss of muscle mass and strength.

The age-related loss of muscle function is known as Sarcopenia, derived from the Greek words for flesh (sarcos) and loss (penia) and its definition includes loss of muscle strength and power, as well as reduced function. It occurs with increasing age, and is a major component in the development of frailty.

The loss of muscle mass during the aging process is important clinically as it reduces strength and exercise capacity, both which are needed to perform activities of daily living.

Age-related changes in muscle structure

With increasing age, we lose muscle mass: lean muscle mass contributes up to 50% of total body weight in young adults, but this decreases to 25% by 75 to 80 years. 

Typical muscle changes with age:

Gross Muscle changes:

• Reduced muscle mass (replaced by increased fat mass)
• Reduced muscle strength
• Slowing on contractile properties and rate of force development

Muscle Fibre changes:

• Atrophy
• Fibre necrosis
• Fibre type regrouping

Effects of endocrine changes on muscle

With increased age, the following changes in endocrine function result in sarcopenia:

• Increased insulin resistance
• Decreased growth hormone
• Reduction in oestrogen and testosterone
• Vitamin D deficiency
• Increased parathyroid hormone

Conditions associated with impairment of skeletal function

• Diabetes
• Metabolic syndrome
• Chronic Obstructive Airways Disease (COPD)
• Congestive Cardiac Failure
• Osteoarthritis
• Parkinsons
• Cancer
• Stroke

Physiotherapy Interventions to minimise or reverse sarcopenia

Resistance exercise training :

The effects of resisted exercise on ageing muscles is the same as for young muscles:

• improved muscle strength
• increased muscle power - power is a product of both strength and speed. Optimal power reflects how quickly you can exert force to produce the desired movement
• improved muscle composition

Evidence:

Population studies

Resistance or weight training has been demonstrated to produce increases in muscle strength and power, and also mobility function, in older people living in the following settings:

1. independently in the community,,
2. in nursing homes,,
3. hospitalised elderly people,

Gender differences

Increased muscle quality from resistance training is a common finding in older adults, and in men there appears to be no difference in young versus old, but there is a study which suggests that older women have a blunted response relative to younger women.

Frequency of resistance training

Frequency of training: studies have demonstrated that resistance training regimes performed once, twice or even three times a week all result in strength improvements.

Length of training programme

There are many studies which clearly demonstrate that older people who participate in resistance training programmes lasting at least 6 to 12 weeks will show increase in both strength and mobility function.

Cochrane Review

The authors collated the results from 121 RCTs examing the effects of resistance strength training exercises, and came to the following conclusions:

"This review provides evidence that PRT is an effective intervention for improving physical functioning in older people, including improving strength and the performance of some simple and complex activities. However, some caution is needed with transferring these exercises for use with clinical populations because adverse events are not adequately reported."

References

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