"Capable till the end"

Time and tide wait for no one. Maintaining skill, capacity and autonomy by using strength and conditioning.

It seems widely accepted that a properly executed resistance training program can improve an older adult’s ability to avoid injuries [1], as well as increase physical function [2],[3] mobility, balance, coordination and reduce the risk of falling. In addition, it has been demonstrated to create more robust psychological well-being [4] and improve social connections [5]. Moreover, physiologically speaking, there seem to be lots of benefits from using a well-thought-out training program, with much of the literature concluding a reduction and even reversal in signs of frailty [6], improvement in contractile function, decrease in muscular atrophy and amelioration in morphology, [7], as well better neuromuscular function, [8] and hormonal adaptations [9].

Physiological inflammation, the good, the bad and the ugly

As we age, our cells undergo a complex signalling process called apoptosis, which could be loosely described as a regulation of non-functional cells, average cell turnover [10], or, more morbidly, pre-programmed cell death [11]. Although it may seem apoptosis is not responsible for the ageing process, it is part of it and could be regarded as essential to maintaining homeostasis [12].

Cytokines are a small group of proteins responsible for regulating the response to disease. Pro-inflammatory cytokines aid in proliferating disease, whereas anti-inflammatory cytokines reduce inflammation and increase healing. Oxidative stress caused by various lifestyle factors can be seen as a promotor of rapid cell death which may increase apoptotic signalling in older or unused muscle fibres, inducing a lack of balance between anti-inflammatory and pro-inflammatory cytokines [13]. Additionally, it seems this may increase the chances of mitochondrial dysfunction [14], apoptotic susceptibility and catabolism [15], therefore reducing protein synthesis, promoting muscle wastage, muscular atrophy and sarcopenia [16]. Sarcopenia can be defined as a reduction in the amount of myofibril satellite cells and or size of muscle fibres [17], which may contribute to a reduced capacity of functional movement in an individual [18]. In addition, it has been stipulated that a decrease in motor units seems to play a significant role in the proliferation of sarcopenia [19], with adults between the age of 60 to 90 years of age experiencing total losses of anywhere up to 50% per muscle group [20].

Fig 1. Cellular and molecular changes that contribute to muscular ageing [22]

N. Miljkovic, J. Y. Lim, I. Miljkovic, and W. R. Frontera, “Aging of skeletal muscle fibres,” Annals of Rehabilitation Medicine. 2015.

Use it or lose it

The Henneman size principle proposes that motor neurons with large cell bodies innervate fast-twitch, high force, more fatiguing muscle fibres. In contrast, small cell bodies innervate slow-twitch, low force and more fatigue-resistant fibres and are done so in order of size, depending on the force output required [21].

The size principle has been the subject of review [22], with some debates relating to motor unit decline, denervation and reinnervation of muscle fibre types. This creates an interesting discussion, especially regarding fast-twitch fibres being denervated and converted to slow-twitch and the possible slowing or reversal of this process when resistance training is incorporated into an individual’s lifestyle [23]. This ability for the body to reinnervate muscle twitch fibres can mean an individual has more ability to contract a higher percentage of muscle fibres, therein improving or maintaining mass and potentially neutralising a deterioration in strength and power.

Fig 2. Shows remodelling or denervation and rein-nervation of fast to slow twitch fibres [19]

Y. N. Kwon and S. S. Yoon, “Sarcopenia: Neurological Point of View,” J. Bone Metab., 2017.

How long have I got doc?

Muscular depletion seems to begin in the 3rd decade of life with reports of a median loss of muscle mass of 0.47% per year for men and 0.37% for women [24], with acceleration occurring from the 6th decade onward [25]. Most rates of muscle loss seem to occur around the hip and lower limbs, with men showing decreases of almost twice that of women [26]. Although many confounding factors contribute to muscle loss, disuse seems to increase muscle wastage at a much higher rate [27]. To further highlight this, significant loss of muscle mass and strength has been shown within healthy young males (23 ± one year) within as little as 14 days of immobilisation, quadriceps muscle cross-sectional area leg lean mass was reduced by 3.1 ± 0.7% (P < 0.01) and strength was decreased by 22.9 ± 2.6% (P < 0.001) [28]. This essentially adheres to the adage of “use it or lose it”.

Mass or Strength?

It has been proposed for there to be a clear definition between loss of muscle mass or “sarcopenia” and a loss of strength which has been determined as “Dynapenia” [29],

with some indications showing differences in these two definitions [30]. Strength has been shown to peak around the 3rd decade of life, with plateaus up until the 4th decade, then a decline at a rate of up to 15% per decade after that, in some instances with men showing a more significant loss in strength specifically eccentrically over women [31].In the interest of progression, more recent literature reviews seem to support the evidence that strength declines faster than muscle mass in both sexes [32]. Strength per unit of muscle gained or lost is measured using various means of testing such as DEXA, isokinetic testing, MRI and muscle biopsy [33], again discussions seem to be inconclusive as to which is the most optimum measurement of muscular deterioration; however, those that have shown a more significant number of variables appears to be a better predictor of individual who is more susceptible to muscle and strength loss combined. [34]. Grip strength seems to play a prominent role in determining overall strength and has been recently promoted as an indispensable biomarker for older adults’ health [35], as well as strong correlations drawn to mortality [36]. Again grip strength peaks in the fourth decade before a steady decline [37]. Although the rate at which grip strength decline seems to vary from study to study [38], some follow-up evaluations have also shown that it is most likely case-dependent, especially among those who regularly participate in resistance training [39].

Fig 3. Shows data collected from 12 studies of male and female grip strength through the decades of life [41] R. M. Dodds et al., “Grip strength across the life course: Normative data from twelve British studies,” PLoS One, 2014.

Are hormones overrated?

Hormonal responses in males and females have also declined with ageing [42]. Testosterone has been shown to stimulate the anabolic effect and increase protein synthesis, which is widely considered an essential factor in strength and muscle growth [42]. However, men can suffer a decline in up to 1.4% testosterone per year from the 4th decade on [43], with women showing a gradual decline up until menopause and after that up to a 60% reduction within a 2 to 5 year period, [44]. Evidence around increased glucocorticoids contributing to the acceleration of sarcopenia over time may be one possible component that could be regulated via bouts of resistance training, creating a balance between cortisol and testosterone [45].

Although most discussions conclude with an advocation around exercise and resistance training programs, appropriate and specific prescriptions seem limited. Assessing the amount of degeneration and frailty might seem an obvious way to determine the different stages of ageing and could help categorise an individual’s abilities. Measurement techniques have been developed, such as the “7-point scale” [46], which includes factors such as age, sex, psychological condition, disease and level of education. This scale has been used extensively to determine health care predictors and protocols; however, when considering preventative measures and longevity, it could be used as a precursor to establishing a training program. If frailty is understood, a possible prescription of training exercises and frequency could be applied.

It is likely to be case-dependent; establishing a level of intensity in strength training sessions throughout the various stages of ageing might seem obvious to apply maximal load testing. However, extreme physical demands of maximal loading may deliver problems regarding the cognitive perception of exertion. An alternative could be isometric pulls with dynamometers and acceleration devices.

Fig 4. Shows one type of model to determine levels of frailty for full exercise prescription [6]

N. W. Bray, R. R. Smart, J. M. Jakobi, and G. R. Jones, “Exercise prescription to reverse frailty,” Appl. Physiol. Nutr. Metab., 2016.

Frequency, volume, intensity and exercise selection would need regulating for individuals within the categories of non-frail, pre-rail and frail [6]. Advocating up to 80% of 1RM elicits higher gains in strength but reduces overall session work time to aid recovery. Other accumulations of data seem to establish a frequency of resistance training up to three times per week, with a volume between two and three sets per exercise and six to ten repetitions, at an intensity of 50 to 70% of 1RM with around two to three minutes rest. This might suggest a low to medium level of hypertrophy training to illicit enough response for adaptation but might lie more in the realms of morphology and functionality to stay within relatively safe exertion levels [48].

The most focus would suggest allowing enough stimulus to create a dose-response to reduce or attempt to reverse frailty (Bray, Smart, Jakobi, & Jones, 2016).

This could be seen as contrary to approaches used in younger populations where healthier physiological systems, cognitive function and techniques allow a more extensive scope of regimes regarding volume and intensity for adaptation.

Power resistance training at higher intensities does seem to have shown more positive results in the strength gains of older populations, but not necessarily functionality [49]. Furthermore, advocating a more explosive style of power movements in training programs might also open further comparisons of older populations with an increased resistance training maturity vs those with little or no experience [50]. Finally, although a discussion of strength training has been the central topic of debate, research showing that ageing diminishes the rate of force development faster than strength [51] could again compound focus within this area of the force-velocity curve.

Comparatively speaking, there have been instances of stark contrast with older masters athletes in weightlifting of up to 85 years of age, establishing 32% peak power and time to reach maximal peak power 13% less in lower extremities over control groups, establishing equal force output and rate of force development to that of a 65-year-old. [52].

This could encourage strength and power training from a younger age to support longevity through physiological systems, highlighting further that specific power training protocols within programs could contribute to the possible discussion of rein-nervation of fast-twitch fibres [19]. Additionally, this may also serve to appropriate a more suitable training outcome for individuals with varying levels of sarcopenia and/or dynapenia, which may, in turn, bring healthy promotion to the benefits of power-based resistance training as well as conventional slow, careful exercise programs for older individuals.

Not one size fits all.

Exercise selection seems to be limited in the discussion, although more recent evidence suggests that mobilising and strengthening the hip and leg with closed chain exercises such as the squat and deadlift should be a primary focus to increase strength and stability during day-to-day activities [53]. Additionally, core, shoulder and upper extremities need to be considered, although this seems individually dependent. As previously mentioned, muscular atrophy occurs faster in the lower portion of the body. Therefore this could seem a valid reason for prioritising more hip-dominant exercises [54]. Less skill-based activities such as simple single joint movements using machines and light weights might reduce the risk of injury and focus more on safety, however, if skill can be improved, multiple joint exercises and potentially Olympic weightlifting derivatives could promote better neural activation and strength and power adaptations [55].

In conclusion - LIFT Lifelong....and maybe a bit quicker.

To conclude, many compounding factors can exacerbate muscular atrophy, sarcopenia and/or dynapenia, which is the primary driver of muscle loss and strength over a lifetime. Although many complex variables play a role and have not been included in the context of this article, there seems to be an extraordinary amount of evidence to suggest that resistance training should be implemented to help slow the process of frailty and ageing and improve functional mobility and overall quality of life.

However, the evidence contained in systematic reviews and meta-analyses tends to conclude in broad parameters regarding training frequencies, volume and intensities, especially regarding the exercise selection [56].

Based on the evidence, a broad spectrum of resistance training protocols covering the entire force-velocity curve could be implemented for older individuals much as they are for younger individuals within reason, providing the correct assessment of needs has been carried out (Bray et al., 2016). Moreover, specific programs should consider implementing power-based training regimes to encourage possible maintenance and/or reinnervation of fast-twitch fibres [23]. Promoting strength training from a younger age might be an obvious solution to shifting positive mental health, possible fear and understanding in a more positive direction [57]. In turn, this might help in reducing possible misconceptions that lifting weights is harmful. Based on the accumulation of evidence, it seems that it is never too late to start, and some exercise is better than none, however with the wealth of information available in this area, it may be lacking the most is specific training protocols with well-designed and executed resistance programs, as well as specific exercise selections. This could border more on educational, social and healthcare-related systems working together with strength and conditioning coaches to improve older individuals’ overall quality of life.

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