Strength training: why it applies to all of us

We’re ageing all the time. The WHO estimates that the percentage of the world’s population over 60 years old will jump from 12% to 22% between 2015 and 2050. The number of over 60s already overtook the number of under fives in 2020. But what does that have to do with ageing?
The ageing process is a widespread phenomenon in the living world [1, 2], but this biological issue has not yet been resolved, and it presents huge challenges for our society.

The effects of ageing on our muscles and the consequences for our health

Ageing is associated with a reduced ability to build strength. This is caused by a number of changes, such as loss of muscle mass [3-7], a shift in muscle fibre types [8-10], muscle architecture and ultrastructure [11-13] and the neural control of muscles [14, 15], which has a considerable effect on the health of older people [16-21].

The skeletal muscles can’t escape the aging process, deteriorating over time [3]. After puberty and in adulthood, healthy people’s muscle mass and strength remains stable. Degenerative processes kick in from around the fourth and fifth decade, which lead to a loss of muscle mass and strength [4]. A recent quantitative study calculated the median loss of muscle mass per decade in men as 4.7% and in women as 3.7% [5]. Up to the age of 80, there’s an age-related loss of around 30% of a person’s maximum muscle mass [6, 7].

However, the loss of muscle mass is not evenly distributed across the whole body, as determined by a MRI study on 200 women and 268 men. The rate of muscle mass loss in the lower limbs was more than double that of the upper limbs [22]. Although men have more muscle mass than women, there is a similar loss of muscle mass in both sexes when viewed as a percentage of maximum muscle mass [22].

The muscle cross-section decreases

The ageing process goes hand in hand with a reduction in cross-sectional area, mainly when it comes to type II fibres [8]. The proportion and volume of type I fibres also decrease [8-10]. Between the ages of 22 and 74, a decrease in type II cross-sectional vastus lateralis muscle area in men has been observed, from 58% to 52% [8]. Considering the fact that the specific tension of type II fibres is 1.4 times higher that of type I fibres [23, 24], this could explain a loss of strength of 2% best, not the 45% determined between these age groups [25]. It’s also remarkable that some studies have not observed any differences in tension between the fibre types [26-28]. So, we can assume with reasonable certainty that a shift of fibre type is only a small part of the age-related loss of strength observed over the ageing process.

Ageing processes have been associated with ultrastructural changes such as increased connective tissue and fat infiltration (image) [29-31]. The area incapable of contracting in older men was double the size of that of younger men, which could be a better explanation for the observed loss of strength than the decrease in type II cross-sectional area [31].

The effects on our health

The decrease in strength in older people can also be attributed to the reduced ability to recruit muscle [14]. The denervation of muscle fibres in rat muscles accounted for 11% of loss of strength [15]. Considering the fact that skeletal muscle mass constitutes up to 40% of total body mass [33], muscle mass and strength loss has fundamental effects on older people’s health, as it’s linked to the risk of adverse effects such as physical disability, poor quality of life and death [16-18].

Furthermore, the close association between skeletal muscle mass and bone density means that loss of skeletal muscle mass results in bone loss. Ostopenia, the loss of bone mass [19], presents a big clinical problem when combined with sarcopenia. Impairment of the musculoskeletal system leads to balance problems and increases the risk of falls, which result in osteoporotic fractures [20]. Low skeletal muscle mass and strength is therefore a driver of public health costs, as a high prevalence of hospital stays has been observed in this cohort [21]. In the United States alone, the total cost of hospital stays of patients with sarcopenia in 2014 was estimated at 40.4 billion dollars [34]. In Switzerland, sarcopenia affected one quarter of all elderly people in 2016 [35].

In the next instalment, we’ll show you how we can improve our quality of life and combat muscle atrophy and loss of strength: I can’t change my age. I’m going to change how I age.

References

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