Muscle strengthening
Approximately half as many adults and older adults in Scotland meet the MS guidelines (31 % of men and 24 % of women) compared to the aerobic PA guidelines (71 % men and 58 % of women [
25]) in 2013. This calls into question whether the current focus on aerobic PA is appropriate particularly given the strong evidence demonstrating the health benefits of MS activities [
4‐
6].
Few countries report nationally representative estimates for the proportion meeting the MS guidelines. Even amongst those that do measure relevant activities at a population level, there are large variations in the definitions and surveillance methods used, which may be obscuring or amplifying real differences. This is important to highlight given the number of inter-country PA comparisons that take place (e.g. GoPA! Country Cards [
26], Active Healthy Kids Country Cards [
27], the Global Burden of Disease studies [
28]).
Within the UK there is a degree of consensus with both England and Northern Ireland using comparable methods to the SHeS [
29,
30]. The proportions meeting the MS guidelines reported in this study are similar to those reported for England in 2012 (34 % of men and 24 % of women) [
29] but are higher than Northern Ireland in 2013/14 (25 % of men and 14 % of women) [
30]. In the USA, participants of the National Health Interview Survey are asked how often they do leisure-time physical activities specifically designed to strengthen their muscles such as lifting weights or doing calisthenics [
31]. The 2014 survey estimated that 28 % of men and 20 % of women in the USA undertook a sufficient quantity of MS activities to meet the guidelines [
32]. In Australia, different surveys use different methods and the estimates for the proportion of adults meeting the MS guidelines range between 9 and 19 % [
33,
34].
Our findings highlight three key groups for policy focus and intervention. Firstly, promotion efforts should be focussed on women, particularly in the youngest age groups. We found the largest percentage point difference between the sexes was amongst 16–24 year olds (57 % compared with 38 %). This is concerning as bone and muscle mass peak in early adulthood and MS activities at this stage in life could help to maximise this and play a role in the prevention of osteoporosis. Both bone and muscle mass have been shown to decrease with age from the mid-20s, with an accelerated decline from age 50 onwards [
13,
35]. This is apparent in both men and women, although hormonal changes associated with the menopause can further exacerbate the decline for women [
13,
35]. Coupled with the fact that women, on average, have a smaller muscle mass than men, this means they tend to cross ‘thresholds for independence’ (the point at which a task cannot be completed independently) earlier [
36].
Secondly, the proportions undertaking no MS sport and exercise activities over the age of 75 (84 % of men and 91 % of women) are concerning as muscle strength is of particular importance to older adults. One reason for this is because of the natural age-related decline of lean muscle mass (termed sarcopenia) [
12]. Studies have estimated the decline to be around 2–4 % per year amongst those over 75 years, but the loss of strength can be 2–5 times faster than that because of other deleterious changes to muscle quality and neural factors [
37]. This loss means that it can be muscle strength that is the primary limiting factor for functional independence [
35], rather than aerobic PA. Low levels of muscle strength increase the risk of falling and sustaining a related injury, can lead to disability, and frailty [
14,
38], all of which have implications for the individual, their carers, and the health services that support them. Strength training has been shown to be equally effective at increasing muscle strength in older adults as in younger adults, sometimes more so [
39].
Thirdly, the 18 % of men and 19 % of women that undertook some but not a sufficient number of sessions of MS sport and exercise activities per week are targets where successful intervention may be more likely. If related to the trans-theoretical model, then these individuals could be considered to be in the ‘maintenance’ phase (i.e. already undertaking a relevant behaviour) [
40]. It is potentially easier for them to increase the frequency of this behaviour to the recommended levels than for those not currently undertaking any to start.
The differences by gender and age of participation in MS sport and exercise activities are similar to the overall participation levels for sport and exercise activities in Scotland [
41]. From this we can infer that, for those activities that require a follow up question to confirm they are a relevant activity, the responses do not vary greatly by age or gender. This suggests that efforts to narrow overall participation gaps go some way to reducing the inequalities in the prevalence of the MS guideline. Our results also highlight hill-walking (for both genders) and golf (for men) as two activities where participation levels are maintained in the older age groups. These are potentially important intervention activities as it has been shown that sustained participation in MS exercise, starting at a young age, provides the greatest protection against sarcopenia [
42].
Although the UK PA guidelines for adults apply from aged 19 [
3], we included 16–18 year olds in our analyses as this aligns with UK health survey reporting and provides more useful information to policymakers. We have undertaken a comprehensive sensitivity analysis: their inclusion makes a ≤1 percentage point difference to the proportions doing no, some and sufficient MS exercise amongst 16–24 year olds and does not change any overall conclusions. The UK guideline relating to MS for 5–18 year olds is combined with that for vigorous intensity aerobic activity: ‘Vigorous intensity activities, including those that strengthen muscle and bone, should be incorporated at least 3 days a week’ [
3]. Given that, if anything, these MS guidelines are greater than for those ≥19 years, we do not feel that this is an unfair misrepresentation.
Balance & co-ordination
We found that less than a fifth of older adults in Scotland (19 % of older men and 12 % of older women) met the BC guidelines in 2012–14. We found no differences in participation by gender, but a decline in the oldest two age groups. However, with such low levels of participation, we recommend that promotion efforts are aimed at all older adults rather than any specific groups.
Loss of the ability to balance is associated with a higher risk of falling and subsequent injury, which in turn can lead to loss of independence, illness, and premature mortality [
43]. BC activities have been shown to be a critical part of an effective falls prevention programme [
38]. One meta-analysis concluded that up to 42 % of falls could be prevented by a well-designed exercise programme that included BC activities [
44].
Although the BC guideline applies to older adults at risk of falls [
3], we included all older adults in our analyses as we were not able identify this ‘at risk’ group from the SHeS. This may have over- or under-estimated the proportions meeting the guideline. If those who are not at risk do not participate in any relevant activities then our estimates maybe lower than the true proportion. However, those who are not at risk may be more active, leading to an overestimation. We recommend that the target population of this guidelines is clarified, as this may hamper any co-ordinated effort to tackle the very low prevalence.
Strengths and limitations
This study is the first to provide detailed analysis of the two forgotten guidelines: MS and BC. We have used routinely collected data to describe the current prevalence levels and identify key groups most in need of intervention. This is important information to take to policymakers to support the case for addressing these issues at a population level. Policy makers in Scotland use the results from national surveillance instruments to make decisions on funding and strategy [
45]. Therefore it is appropriate to use these same data in this analysis, as it has most relevance for future policy decisions. The face validity of the SHeS method of measuring prevalence of population meeting the MS and BC guidelines is questionable as it is limited to sport and exercise activities. Although this is more inclusive than other national approaches to measuring MS that are often restricted to weight training or activities that would be categorised in the domain of sport and exercise [
34,
46,
47]. Activities such as heavy gardening and carrying heavy loads are not included despite being listed as example activities in the guideline document itself [
3]. Another limitation of the SHeS questionnaire is that certain activities are grouped together or cover a wide range of activities (e.g. workout at gym/weight training/exercise bike, or exercises) and it is not possible to establish which of the activities was undertaken and what exactly they involved.
As with all surveys, errors may arise at any stage: design, data collection, processing, and analysis [
48]. One that is difficult to account for is the self-report nature of the data. It is possible that the reported levels of MS and BC activities differ from the true levels [
49]. We add our support to calls to reach an international consensus over which activities should count towards the guidelines, how best to measure them at a population level [
34], how to ensure they are of sufficient intensity, and then to investigate validation methods so that the degree of error can be better understood. Other factors such as sampling error or non-response bias are mitigated by the weighting procedures that result in a nationally representative sample on key demographic variables (see Bromley et al. (2015) for further details [
22]). However, there remains a degree of uncertainty around the estimates and this should be considered in their interpretation.