Exercise as it relates to Disease/Can physical activity slow the development of sarcopenia as we age?

This page is a critique of the article 'Yearlong physical activity and sarcopenia in older adults: the Nakanojo Study' by H Park, S Park, R J Shephard and Y Aoyagi in 2010.

What is the background to this research?
Sarcopenia is described as the progressive decline and loss of skeletal muscle mass and strength as one ages . A number of potential variables have been associated with the development of sarcopenia such as physical activity level, hormone deficiencies and dietary protein intake. As muscle function is a determinant of physical ability, sarcopenia can affect quality of life and consequently ability to maintain independence  . Many studies have found a direct link between physical inactivity and the progression of sarcopenia.

The relationship between habitual exercise and sarcopenia is one that is of importance. By understanding this relationship, the development of sarcopenia in the elderly population can be further understood and factors associated with the onset of the disease recognised.

The authors, Park, Park, Shephard and Aoyagi, hypothesised that there would be a positive association between habitual physical activity and muscle mass. While there have been a range of studies investigating the relationship between physical activity and sarcopenia, many are somewhat biased as they are based on self-reports or are very short in duration. This study spanned one year and used a pedometer/accelerometer for data recording, making the study representative of everyday physical activity.

Where is the research from?
This research focuses on elderly people living in Nakanojo, Gunma, Japan. As the study focuses on a small Japanese population, the results collated may not be reflective of other socio ethnic groups. For example, it has been observed that typically, Japanese individuals tend to be thinner than individuals of European or American descent and this may impact the study.

This study ‘Yearlong physical activity and sarcopenia in older adults’, is part of the Nakanojo study. Published in the European Journal for Applied Physiology, the study was conducted by H Park, S Park and Y Aoyagi from the Tokyo Metropolitan Institute of Gerontology as well as R J Shephard from the University of Toronto. Focusing on the Japanese population, the Nakanojo studies investigate the relationship between physical activity and a number of health aspects including physical and mental health. Park, Park, Aoyagi and Shephard are associated with many of these studies, but not all of them.

In addition to the studies included in the Nakanojo study, these authors have also produced a number of different publications, focusing on a range of health issues. Knowing that these authors have reputations in the field of health research and investigation, a combination of their knowledge is beneficial for this study.

What kind of research was this?
The results in this original study were cross-sectional. Cross-sectional studies are especially useful when investigating two different variables. In this study they observed the relationship between physical activity and the development of sarcopenia. Exercise level and intensity was compared to appendicular muscle mass.

What did the research involve?
Taking place between July 2002 and June 2003, the study comprised of 78 male and 97 female Japanese citizens all between the ages of 65-84. Those that took part in the study were ambulatory as well as free of any orthopaedic problems, cognitive impairments, myopathies and any chronic or terminal illnesses.

Participants were asked to wear an accelerometer/pedometer constantly for 1 year, 24 hours per day. The study focused on the duration and intensity of physical activity as well as appendicular muscle mass. Intensity was assessed using metabolic equivalents (METs). It was decided that the intensity at which daily physical activity would be performed would be set at >3 METs, which is equal to a moderate intensity. The pedometer/accelerometer recorded daily step counts and the intensity at which the individual was working. Skeletal muscle mass was measured using a whole-body dual X-ray absorptiometer (DXA) following the intervention. This allowed for assessment of muscle mass associated with the physical activity being undertaken.

The study had multiple limitations in the methodology:

The pedometer/accelerometer:
 * Errors in distance walked could have been encountered when an individual was walking uphill or downhill.
 * The pedometers response to resisted movements varies and is somewhat limited.
 * These factors possibly limit the estimate of total energy expenditure as well as the association with muscle mass.
 * Despite this, it was seen that step count remained unchanged and accurate.

The DXA:
 * Participants were only scanned by a DXA at the end of the study.
 * This allows a direct correlation between muscle mass and sarcopenia, but does not allow comparison of changes in muscle mass with sarcopenia.
 * If a DXA was performed at the start of the study, the findings could potentially be strengthened.

What were the basic results?
Results presented a number of notable findings. Values for appendicular muscle mass, year-averaged step count and year-averaged duration of physical activity were noticeably different between individuals. Those that were considered sarcopenic tended to have values lower for all 3 categories compared to those that were non-sarcopenic. When compared to sarcopenic individuals, non-sarcopenic individuals demonstrated to be of younger age, reiterating the fact that the disease is age related. Furthermore, non-sarcopenic individuals demonstrated to also be heavier and taller. It was found that participants between the ages of 65-74 had a higher duration of exercise that was >3METS compared to those between 75-84. Non-sarcopenic individuals also exhibited a greater duration of exercise.

Overall, males and females that had step counts of 7000 to 8000 and/or spent 15 to 20 min/day engaging in physical activity at intensities greater than 3 METs were likely to have muscle masses exceeding the sarcopenic threshold. Muscle mass tended to increase with habitual activity that was performed at a moderate to vigorous intensity.

What conclusions can we take from this research?
From the results presented in this study, it can be concluded that habitual exercise is beneficial in slowing the development of sarcopenia. By engaging in a minimum of 15-20 minutes of physical activity (walking) at a moderate intensity, and maintaining between 7000 and 8000 steps a day, an individual can significantly slow progression of sarcopenia.

A meta-analysis published in 2017 came to the same conclusion. It found that overall, individuals that engaged in physical activity were at a lower risk of developing sarcopenia. This is consistent with the findings of Park, Park, Shephard and Aoyagi.

Practical Advice
Taking the conclusions from this study, together with others, it is easy to say that physical activity has a strong relationship with the onset and progression of sarcopenia. In the case of older individuals, ensuring daily physical activity is of importance as maintaining muscle mass is imperative to slowing development of sarcopenia.

When undertaking physical activity or wanting to increase the level being undertaken, it is important to ensure it is safe to do so. This is especially important for older individuals and those with underlying health conditions. Consulting a medical professional would be beneficial for individuals with significant levels of sarcopenia, so that an appropriate exercise plan can be developed.

Further Information/Resources
2018 AIMSS Fact Sheet: https://aimss.org.au/wp-content/uploads/2018/07/Sarcopenia-Day-factsheet-for-Patients.pdf

ANZSSFR Website: https://anzssfr.org

Exercise and Sarcopenia: https://www.racgp.org.au/afpbackissues/2006/200603/200603taaffe.pdf