Background
The risk of progressive decline in skeletal muscle mass and strength, termed sarcopenia, increases with age, chronic disease, physical inactivity and poor diet [
1‐
3]. Nutrition is an important part of muscle mass and function [
4‐
6]. Since muscle function is affected by poor nutrition, hand grip strength (HGS) has become a marker of nutritional status [
7‐
9] and an outcome predictor for nutritional interventions [
9]. HGS is a key component of major sarcopenia definitions (the Foundation for the National Institutes of Health Sarcopenia Project and European Working Group on Sarcopenia in Older People, January 2019 update [EWGSOP2]). HGS has also been correlated with a number of performance measures, including the timed up and go (TUG) test [
10], which predicts changes in functional balance [
11] and was introduced as part of EWGSOP2 as a measure of sarcopenia severity. Likewise, the 400 m walk test was introduced within the EWGSOP2 definition to assess mobility and endurance, in conjunction with chair stands (strength) and the well-established sarcopenia component gait speed (GS) [
12].
Low protein and energy intakes are linked to sarcopenia [
5,
13] and benefits of appropriate nutrition have been reported alone and in conjunction with resistance training [
14,
15]. Although the provision of exercise programs in aged-care centres is not uncommon [
16‐
18], there is a lack of data on the relationship between sarcopenia components (muscle strength, lean mass and physical performance) and physical activity levels and nutritional status amongst participants using Helsinki University Research (HUR) and conventional gym equipment.
Our aim was to examine and compare associations of sarcopenia components with self-reported physical activity and nutrition in older adults performing exercise training at HUR and conventional gyms. We hypothesized self-reported physical activity and nutrition would be associated with muscle mass and function, with no differences according to the type of gym being used (HUR or conventional gym training).
Discussion
In this study, only GS (but not muscle strength) at both HUR and conventional gyms was positively associated with PASE scores, indicating higher self-reported activity is associated with better GS. This is similar to previous reports of PASE scores being positively correlated with GS [
27], underlining the importance of maintaining physical activity additional to any gym sessions. Our results are inconsistent with evidence that low PASE scores, indicative of low physical activity, are related to muscle strength in older adults [
31], as we did not find any association between muscle strength and PASE. It is likely that if baseline data was available, associations with strength might have been stronger, but due to participants already taking part in resistance exercise training programs designed to improve muscle strength, these associations were missing.
Rizzoli et al. [
32] report that associations between self-reported and performance-based measures range from small to medium, with GS and CS among the most responsive performance-based measures. Only in the HUR gym group, 400 m walk was negatively correlated with PASE, indicating that higher levels of physical activity are associated with faster walking speeds and better endurance. Given the above, PASE appears to be a useful survey tool for correlation with measures within lower leg mobility/speed, and GS and 400 m walk continue to be positively influenced by physical activity additional to concurrent resistance training.
In our whole sample, the PASE mean score of ~ 127 was higher than reported for US (M: 103) [
27], Malaysian (M: 95) [
33] or Turkish community-dwelling older adults (M: 122) [
34]. A higher PASE score of our cohort indicate that our participants are not only community-dwellers, but have been undertaking resistance training for over a year on average. Those who attend gyms should be encouraged to not view it as their only form of exercise, but ensure it is in addition to their regular physical activity. A recent study asked 103 Australians aged 50–92 years about sustainable lifestyles [
35]. Thirty percent regarded exercise as a priority; of which 11% mentioned irregular activities (e.g., gardening and walking), another 11% purposeful exercise (e.g., gym and water aerobics) and 8% regular exercise (e.g., golf and tennis) [
35]. Boulton-Lewis et al. argue that lack of awareness of exercise benefits and barriers are not new, emphasising the importance of measuring motivation and engagement to develop strategies to enhance physical activity.
None of the sarcopenia components were associated with the ARFS total score. There is limited literature on relationship between ARFS and muscle mass and function. Past research shows that a higher ARFS is linked with higher intakes of micronutrients and lower percentage energy from total and saturated fat in middle-aged populations [
36]. Based on a total score of 73 for the ARFS [
30], our mean results of ~ 36 for both gym groups were only slightly higher than that reported in middle-aged Australian women (M: 33), suggesting that although their diet could be improved, they may be outperforming younger ages [
37]. Indeed, 33 and 39% of HUR and conventional gyms, respectively, achieved ARFS 39 and over, which is higher than that reported (21%) of middle-aged Australian women with ARFS over 40 [
37]. Our higher ARFS results in two-thirds of both gym participants imply healthier eating patterns and higher diet quality.
Studies show that low protein and energy intake is linked with sarcopenia [
5,
13]. There is also a strong correlation between lean mass and nutritional status in older populations [
38]. Lower ALM/h
2 was significantly associated with lower self-reported protein and energy intake in both gym groups, supporting that sufficient energy intake, and protein specifically, is essential for skeletal muscle maintenance. Our results do not show any correlations for self-reported protein/energy intake with HGS. This is inconsistent with prior research showing that since muscle function is affected by poor nutrition, HGS has become a marker of nutritional status [
7‐
9] and an outcome predictor for nutritional interventions [
9].
Again, given our participants are specifically training for strength, this may have masked any effect of poor nutrition or lower protein intakes. The HUR group had significantly higher self-reported protein intake, which may be related to the fact that they also tended to have higher BMI than the conventional gym participants. The most recent national data (2011–2012) state protein intake for the general population is around 98 g/day and 86 g/day for men in the 51–70 and 71+ age groups, respectively, and for women it is 78 g/day and 73 g/day, respectively [
39]. Thus, our results suggest that our cohort consumed more protein than average, especially the HUR gym group. It is possible that participants are not obtaining as great a benefit from engaging in exercise than they would if their protein intakes were higher or of better quality (not quantity) and timed more appropriately. It is very well established, at least in younger individuals, that ingesting high-quality protein with training augments the beneficial effects [
40‐
42]. However, older individuals require higher amounts of protein to increase protein synthesis at the same levels as a younger individual [
43‐
45], and the recommended dietary intake (RDI) is based on not becoming deficient, rather than being an optimal dose. Nowson and O’Connell [
46] report that 1.0 to 1.2 g/kg/day dietary protein is recommended for older adults or even more for those exercising and physically active to reduce muscle loss with age. A recent meta-analysis reports that muscle mass increase required protein intakes of up to 1.6 g/kg/day and was more effective in resistance-trained people but less effective in people over 60 years [
45]. Protein synthesis is higher with whey protein, which is digested quickly and lower with casein, which is digested slowly, implying that a quick protein may be more suitable for reducing protein losses in older populations [
46].
Timing of protein intake in combination with exercise also needs to be considered [
46]. It has been reported that community-dwelling and frail older Dutch adults with a dietary intake of 1.1 g/kg/day and 1.0 g/kg/day, respectively, consumed insufficient protein at breakfast and the frail group also consumed insufficient protein at lunch (> 30 g), which was below the intake needed for muscle protein synthesis, thus likely contributing to negative health outcomes and poorer physical activity levels [
46]. As a result, there is opportunity to enhance distribution of protein consumption across the day in older populations [
46]. As most participants in this study had engaged in resistance training for some time, it is likely that protein quality and timing may be affecting potential for muscle mass and function gains. Thus, guidance on improving protein quality and timing of ingestion should be provided to improve lean mass health.
It is recommended regular physical activity, in addition to existing gym-based exercises, and education on nutrition be promoted at both gyms. Practical implications are that practitioners could use strategies incorporating exercises (particularly resistance training) and appropriate nutritional advice to prevent loss of muscle mass and muscle strength. Future research should incorporate post-tests to examine effects of training.
There are some limitations in our study. Since baseline data was not available, many associations did not exist as participants may have improved their muscle mass and function with training over time. The low sample size of the conventional group and not being able to show the net effect of the interventions resulted from the cross-sectional nature. The 400 m walk test had to be modified to a 10-m course walked 20 times rather than the standard 20 m walked 10 times back and forth given available space in the gyms. Results of this study may not be generalised to the general population as subjects were limited to older exercising adults in Melbourne, Australia.
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