Resistance training for older adults and the conditions of the STAR triad.

Everybody is ageing, and with age there are several conditions that will sooner or later affect all of us.  Most people will have seen these conditions in ageing relatives and will have an intuitive understanding what their effect on quality of life is.  Difficulty moving and experiencing pain when performing activities of daily life are very common among older people.  Simple activities like raising from a chair, climbing stairs, or reaching overhead for objects can become real challenges.  Responsible for the debilitating effects of ageing is in most cases, not just one but a complex of conditions, that are inter-related.  In a recent review, Minetto, et al (2020) coined the acronym STAR for this complex of disorders that includes sarcopenia, tendinopathy and arthritis.  Tendinopathy is a pathology where affected tendons show a decline in function, reduced tolerance to exercise and pain, caused by disorganisation of collagen fibres, increased sensory nerve innervation, and an increase in immune response and inflammatory markers (Millar et al., 2021).  Sarcopenia is defined as the loss of muscle strength as a consequence of, or when it coincides with low muscle quantity and quality (Cruz-Jentoft & Sayer, 2019).  Arthritis is a condition where joints are affected by swelling, stiffness and pain and the breakdown of tissues within the joint, which can have multiple causes like autoimmune reactions, infections, wear and tear and damage from previous injuries (Arthritis – Symptoms and Causes, n.d.).  According to Minetto (2020), it is important to recognise how these three conditions are affecting each other and that they have to be evaluated comprehensively.  Examples for the interconnectedness within the STAR triad are, the increased risk of knee and hip osteoarthritis caused by quadriceps weakness (Godziuk et al., 2018), or insufficient hip abductor function leading to gluteal tendinopathy (Plinsinga et al., 2019).  As both, tendinopathy and arthritis are painful conditions, they tend to lead to avoidance patterns which contribute to more loss of muscle mass  and strength (Vlaeyen & Linton, 2000).  And even when physically active, pain can interfere with the neural mechanisms of motor control at different places in the nervous system, for example reducing force production of the quadricep muscle, when the knee is affected by osteoarthritis (Kittelson et al., 2014).  So, it becomes clear that the interaction between all three conditions within the STAR complex can create a positive feedback loop that contributes to the decline of quality of life and independence of the ageing individual affected.  The good news is that all three conditions of the STAR triad have a common way of treatment and prevention:  They can be kept in check with exercise alone or in combination with other lifestyle interventions like nutrition (Cruz-Jentoft & Sayer, 2019; Maganaris et al., 2017; McAlindon et al., 2014).

Exercise of all kinds can be seen as beneficial for ageing individuals affected by one or more conditions of the STAR triad (or for the prevention of it), but one form of exercise is particularly effective in preventing loss of muscle strength and sarcopenia.  Resistance training has shown to be the best tool in preventing and improving the effects of age related loss of muscle strength and sarcopenia, and thus positively effects the outcome of tendinopathy and arthritis (Linqian Lu et al., 2021).  The central mechanism by which resistance training can help to battle the STAR triad is by maintaining or even building muscle mass and function (Cooney et al., 2011).  The actual age and the progression of the condition of sarcopenia seems to be largely irrelevant as resistance training at the right intensity and volume seems to improve the condition regardless of the above.  In a study by Vikberg (2019) the hypertrophic effect of a 10-week resistance training programme has shown to be present in all participants of the intervention group with a mean age of 70 years with pre-sarcopenia. 

Although resistance training has a generally good effect for the prevention and treatment of sarcopenia, special considerations must be involved when working around the limitations caused by arthritis and tendinopathy.  In the case of tendinopathy, a popular and effective non-operative treatment and training protocol is the application of eccentric exercises (Visnes & Bahr, 2007).  Even though it is unclear which exact form of eccentric training has the best result in ameliorating the effects of (in this case: patellar) tendinopathy, it seems that drop squats and slow eccentric movements, and exercising-until-tendon pain, all seem to be having a positive outcome on follow up after 12 months when compared to surgery (Bahr et al., 2006).  Recommendations for the frequency and volume of affective eccentric trainings reach from three sets of 15 repetitions three times a week to three sets of 15 repetitions two times daily depending on the actual workout protocol (Visnes & Bahr, 2007).  At this point it is important to mention that these recommendations are based on the work on younger athletes with tendinopathies as a result of overuse, and likely need adjustment when applied to an older cohort.  The underlying mechanism by which eccentric exercise affects tendons and their collagen matrix remains the same, though the rate of improvement is likely to be slower in older people due to slower turnover rates within the tendon tissue (Svensson et al., 2016). 

The detriments of an arthritic condition are similar to those of tendinopathy with pain stiffness and the tendency to be physically inactive.  However, an affective resistance training programme for the improvement of a by osteo- or rheumatoid arthritis effected individual might differ from the previously described.  A comparison of concentric and eccentric training showed slightly better outcomes for pain and strength gains after four weeks in the eccentric training group, but with a high variability which indicates a need for individualisation of training methods and programmes (Vincent et al., 2019).  But because of the lowered tolerance for training loads in individuals affected by arthritis it might be beneficial to make use of a technique called blood flow restriction training.  Blood flow restriction training has the benefit of achieving similar improvements in muscle strength and cross sectional area (hypertrophy) with much lower loads when compared with traditional high intensity resistance training (Vechin et al., 2014).  This method involves occluding or restricting the venous blood flow from the limb that is performing the workout and to complete all sets with an intensity of only 20% to 30% 1RM with an occlusion pressure of  80mmHg to 150mmHg (without opening the occlusion cuff in between sets) (Heitkamp Hc & Heitkamp, 2015).  As a result of the restricted blood flow it seems that muscle activation and fibre recruitment is at levels usually only seen when working with heavier loads especially in older untrained people (Takarada et al., 2000).  Moreover, this form of training also has shown to increase pennation angles of the trained muscle which is a morphological change that leads to increased muscle strength (Kubo et al., 1999).  But the best part is that low intensity resistance training with blood flow restriction seems to stimulate muscle growth on par with high intensity resistance training, likely because of elevated levels of hormones such as insulin like growth factor 1 (IGF1), vascular endothelial growth factor (VEGF), growth hormone (GH), and interleukin-6 (Patterson et al., 2013).  Because of the limitations in the research regarding exact training protocols, levels of blood flow restriction, and long-term effects, this form of training is probably best applied and supervised by a fitness professional or physician with sufficient experience in applying this technique. However, blood flow restriction training was affirmed to present no greater risk as traditional strength training (Hughes et al., 2017). 

Further benefits of resistance training with predominantly vertical movements (like squats) that do not affect the muscle as such, are improved bone properties like density and diameters (Johansson et al., 2015).  Resistance training can also assist to prevent and manage the effects of type-2 diabetes by improving insulin sensitivity, reducing HbA1c, and increasing the density of glucose transporter type 4 among others (Westcott & Wayne L. Westcott, 2012).  The best way to prevent age related strength and muscle loss it to start resistance training early in life (midlife) and to maintain muscle mass and joint health for as long as possible (Naseeb & Volpe, 2017).  However it is never too late to start resistance training, but as with any new physical activity, picking up a new form of resistance training has the potential to cause sore muscles and might temporarily worsen the joint pain experienced (Liu & Latham, 2009).  To support the build-up, maintenance, and function of muscle mass one can follow a few simple dietary recommendations.  Firstly, for older people it is recommended to increase the daily amount of protein to 1.3 – 1.4 g per kg of bodyweight (lean body mass) per day (Naseeb & Volpe, 2017).  Secondly, the reduction of dietary sugar and refined carbohydrates in the diet can help to reduce the disrupting effects of glucose related metabolites (advanced glycosylated end products or AGEs) on the rebuilding of tendons and other tissues in the body (Svensson et al., 2016).  For more details on that please follow this link to a related blog article.  Additionally there is some evidence that sufficient Vitamin D supplementation (optimal serum levels of 30 to 60 ng/mL) has a positive effect on muscle strength in older adults (Antoniak & Greig, 2017), on top of the well known benefits of healthy bones, management of calcium and phosphate levels, immune function, and many more (Basit, 2013). In conclusion, resistance training is an excellent tool in the pursuit of musculoskeletal health in older people at risk of developing, or with signs of the conditions of the STAR triad.  Depending on the severity and combination of conditions there is some form of resistance training that will have a positive effect on the affected person, especially when the intervention is tailored towards the individual needs of the condition and person.  In general, it is recommended to prevent the conditions of the STAR triad by including resistance exercises into the lifestyle early on.  Additional lifestyle measures like diet can support and enhance the positive effects of resistance training for older people.

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