Aerobic physical activity and muscle-strengthening exercise guideline adherence in Germany: ndings from a national sample of 24,016 adults

Background The German ‘National Recommendations for Physical Activity and Physical Activity Promotion’ state that adults ( ≥ 18 years) should engage in: [i] ≥ 150 minutes of aerobic moderate-to-vigorous-intensity physical activity/week (MVPA); and [ii] ≥ 2 days/week of muscle-strengthening exercise (MSE). However, there is limited research on the adherence to these guidelines among German adults. The present purpose was to describe the prevalence and correlates of physical activity guideline adherence among a nationally representative sample of German adults. Methods Data were drawn from the 2014 German Health Update survey, collected via a combination of web-based and mail surveys. Self-reported physical activity levels were assessed using the previously validated European Health Interview Survey Physical Activity Questionnaire. Weighted prevalence levels of the sample meeting the aerobic MVPA ( ≥ 150 minutes/week), MSE ( ≥ 2 times/week) and combined MVPA-MSE guidelines were calculated. Poisson regressions were used to assess prevalence ratios for physical activity guideline adherence categories across sociodemographic (age, sex, socioeconomic status) and lifestyle-related (self-rated health, BMI) variables. Results Out of 24,016 participants (response rate = 27.6%), aged ≥ 18 years, 45.3% (95% CI: 44.5-46.0%), 29.4% (95% CI: 28.7-30.1%) and 22.6% (95% CI: 21.9-23.2%) met the aerobic MVPA, MSE and combined guidelines, respectively. Population sub-groups independently less likely to meet the combined guidelines included those with poor self-rated health, low socioeconomic status and those being overweight or obese. As almost 80% of German adults not meet the nationally recommended combined aerobic MVPA-MSE for large-scale promoting both aerobic MVPA and MSE. meeting the MSE guideline; [iii] meeting/not meeting the combined MVPA-MSE guidelines. Each model included the following explanatory variables: sex (reference group [ref] = “male”); age (ref = “18-29 years”); socioeconomic status (ref = “high”); nationality (ref= “German”); self-rated health (ref = “very good”); and BMI (ref = “normal weight”). For these Poisson regression analyses, PRs and their 95% CIs were reported.

guideline alone, meeting both aerobic MVPA-MSE guidelines is prospectively associated with lower risk of all-cause mortality [13,14].
Despite joint aerobic MVPA-MSE being nationally recommended, there is limited available data describing its prevalence and correlates among German adults. German public health surveillance studies have typically solely examined the population-levels of aerobic MVPA guideline adherence [9], with self-report estimates suggesting that 50% of adults meet the aerobic MVPA guideline [15,16]. A recent report showed that 29.4% of German adults reported meeting the MSE guideline, and 22.6% met the combined MVPA-MSE guidelines, with guideline adherence declining with age and education and males having a higher prevalence, compared to females [17]. However, limitations of that report, were rst, physical activity guideline adherence across other key sociodemographic/lifestyle factors were not included (e.g. socioeconomic status, self-rated health, body mass index) [18], and second, a multivariable analysis was not conducted. Reporting of physical activity levels by population sub-groups is vital for determining the most 'at-risk' populations [19], and essential to inform/guide optimal public health policy. Moreover, such research could be used to enhance the success of future large-scale physical activity interventions within Germany.
The primary aim of this study is to determine the prevalence of MVPA, MSE and combined MVPA-MSE guideline adherence among a representative sample of German adults. A secondary aim is to examine how physical activity guideline adherence varies across sociodemographic/lifestyle factors. provided informed consent to participate. The purpose of the GEDA is to provide a health monitoring survey that produces reliable information on the actual German adult population's health status, health determinants and health care utilization [20].

Methods
A overview of the methods used in the GEDA 2014 is available elsewhere [20]. Conducted between November 2014 and July 2015, a two-stage strati ed cluster sampling approach was used to recruit persons aged ≥18 years with permanent residence in Germany.  [17,20].
In the current study, we only included data from those who fully responded to the physical activity items. To increase generalisability, we did not apply any further inclusion/exclusion criteria [21][22][23][24]. Additionally, since the German physical activity guidelines for MVPA and MSE apply to both adults (aged 18-64 years) and older adults (aged ≥65 years) [9], we included adults aged ≥18 years.
Physical activity (aerobic MVPA and MSE) assessments Self-reported physical activity levels were assessed using the European Health Interview Survey Physical Activity Questionnaire (EHIS-PAQ) [25]. The EHIS-PAQ has been shown to be a reliable and valid physical activity assessment tool for use in public health surveillance, and an overview of the development, design and psychometric testing this instrument has been described elsewhere [25] Aerobic MVPA Consistent with standardised protocols [25], to count towards meeting the aerobic MVPA guideline, we included physical activity accrued within the domains of: [i] moderate-to-vigorous aerobic recreational physical activity (e.g.
Nordic walking, brisk walking, ball games, jogging, bicycling, swimming, aerobics, rowing, badminton); and [ii] transport-related physical activity (e.g. walking/cycling). For these two domains, respondents were asked to consider physical activity during a 'typical week', with the bout of activity having to last for ≥10 minutes. In each domain, respondents also were asked to report the number of days per week and total time spent (hours/minutes

Muscle-strengthening exercise
To assess participation in MSE, respondents were asked, "In a typical week, on how many days do you carry out physical activities speci cally designed to strengthen your muscles such as doing resistance training or strength exercises? Include all such activities even if you have mentioned them before.". When considering this question, respondents were prompted to consider a range of MSE-related activities, such as resistance training, strength exercises (using weights, elastic band, own body weight, etc.), knee bends (squats) and push-ups (press-ups). This item has shown to have 'fair' test-retest reliability (ICC= 0.55) [25], and similar items have shown evidence of concurrent validity, using the two or more MSE days/week threshold against metabolic syndrome [26].
According to the German physical activity guidelines [9], participants were dichotomised as either;  [21][22][23][24], and sub-categories were created to be consistent with previous studies from the GEDA 2014 [27]. Socioeconomic status (low, medium or high) was assessed using the previously validated, German-speci c, Socioeconomic SES index (SES Index) [27]. An overview of development of the SES Index can be found elsewhere [27]. The SES Index is based on information from three constructs: [i] formal education/vocational training; [ii] occupational status; and [iii] equivalenced to net household income. This index is calculated as a total points score on the basis of the point values assigned to each construct. A distribution-based distinction of three status groups is made for the analyses, with the low and high status groups each comprising 20% and the medium status group 60% of the population [27]. Self-rated health was assessed on a 5-point scale (1= 'very good' to 5= 'very poor'). BMI was calculated based on self-reported measured height and weight, and categorised into: <18.5 kg/m 2 (underweight); from ≥18.5 kg/m 2 to <25 kg/m 2 (acceptable weight range); from ≥25 kg/m 2 to <30 kg/m 2 (overweight); and ≥30 kg/m 2 (obese).

Statistical analysis
All statistical analyses was conducted using Complex Sample Module, IBM SPSS 24.0 statistical software (SPSS Inc. an IBM Company, Chicago, IL). To enhance population representativeness, each GEDA 2014 responded was provided with a sample weight to correct for non-response. Detailed information on the methodological considerations for the sample weights in the GEDA 2014 is available elsewhere [28,29].
To assess the primary study aim, weighted percentages and their 95% con dence intervals (95% CI) were calculated for: [ (30,31). b To meet the MVPA guideline respondents had to report engaging in at least 150 minutes per week of moderate-intensity physical activity or 75 minutes of vigorous-intensity physical activity per week, or an equivalent combination both, and accumulated in bouts of at least 10 consecutive minutes during leisure time and for transport. c To meet muscle-strengthening exercise guideline the guideline respondents had to report engaging in muscle strengthening activity at least two days per week. d Meeting both guidelines. e Raw unweighted number of responses. f Weighted percentage. g Numbers different to total sample due to missing responses.

Discussion
Approximately 80% of German adults did not meet the nationally recommended physical activity guidelines of ≥150 minutes per week of aerobic MVPA and MSE ≥2 days per week. Considering that evidence that combined aerobic MVPA-MSE is independently associated with a multiple bene cial health outcomes [13,14,22,26,30], our ndings suggest the need for immediate public health action to address physical inactivity in Germany.
The physical activity prevalence estimates (both aerobic MVPA, MSE and combined MVPA-MSE) presented in the current paper suggest that inactivity among German adults is currently underestimated. A recent study based on pooled data from several national public health surveillance surveys worldwide from 2002-2016, stated that 42.2% of German adults (≥18 years) were classi ed as inactive [15]. However, the German data analysed in that study included physical activity estimates solely based on meeting/not meeting the aerobic MVPA guideline [15]. The present data suggest that when considering the prevalence of adults not meeting the combined MVPA-MSE guidelines (77.4%), physical inactivity among German adults is almost two-fold greater than estimates exclusively based on aerobic MVPA guideline adherence.
The aerobic MVPA guideline adherence estimated in the current study are consistent with previous studies on German adults [15,16]. Cross-country comparisons show that a slightly higher prevalence of German adults meet the combined guidelines compared to U.S. [22] and U.K. [7] (22.6% vs. ~20.0 %). In contrast, lower MVPA-MSE guideline adherence estimates have been observed among Australian [24], and Finnish adults [31] (10.8%-15.0%) For MSE guideline adherence, somewhat similar cross-country patterns to those for meeting the MVPA-MSE guidelines have been observed [22,24,31], with Germany levels comparable to U.S and U.K [7,23], but higher than those from Australian [24] and Finnish studies [31].
With the inclusion of a larger number of sociodemographic/lifestyle factors and the use of a multivariate adjusted analysis, the current study expands on a pervious report from the GEDA 2014 [17]. The lowest likelihood of meeting the combined MVPA-MSE guidelines were identi ed among those with poorer self-rated health, lower socioeconomic status, the overweight/obese and females. These sociodemographic/lifestyle correlates of combined MVPA-MSE guideline adherence are somewhat congruent with studies from other countries [21,22,24], and indicate that within the German context, these population sub-groups should be the target for future physical activity interventions.
Studies from Australia, Finland and U.S. have shown an inverse age gradient for the likelihood of meeting the combined MVPA-MSE guidelines [21,22,24]. Therefore, it was surprising to observe in our sample of German adults no such age gradient. For example, the second youngest group (30-44 years) had lower APR, when contrasted with their older counterparts (≥45 years). The increased physical activity among older populations is consistent with German research -especially for women [32]. While the causes of this are yet to be fully established, it might be that older German adults are better informed and more aware of health bene ts of physical activity. This may positively in uence being active especially among older populations who are perceiving health problems. Additionally, children leave the parental home (empty-nest-phase), so especially women have more time resources and sports clubs in Germany offer several activities, which are tailored to women [32]. Clearly, more research is needed to rst, replicate this nding in prospective studies, and second, to determine its causes, especially for the decrease of physical activity in the younger age group. Nonetheless, the age-speci c physical activity patterning shown in the current study might be re ective of increasing demands/life commitments encountered as German population's transition out of young adulthood into middle adulthood.
The nding that ~70% of German adults do not meet the MSE guideline indicates that this physical activity may warrant future national public health attention to increase population-level engagement. However, compared to aerobic MVPA, as with other countries [23,24,33], the promotion of MSE has been of limited focus in previous Germany public health promotion [9]. Importantly, our study showed that compared to those reporting insu cient aerobic MVPA, greater proportions report insu cient MSE (70.6% vs. 54.7%). Future large-scale public health MSE promotion approaches should include a combination of approaches [23]. Potential simultaneous and multi-level MSE strategies could include; providing physical environmental support (e.g. access to tness centres/equipment in open spaces) [34], policy support (e.g. subsiding equipment for home-based activity, gym memberships, access to quali ed tness professionals) and mass-media campaigns challenging the negative stereotypes often linked to MSE (e.g. high injury risk, excessive muscle gain) [35,36]. environmental factors (location of/access to facilities etc.) [18]. In particular, research on modi able factors related to MSE will be of interest when developing public health interventions.
A key limitation of this study is the use of self-report MVPA-MSE assessments. We are unable to exclude the possibility this method led to common problems associated with self-report physical activity assessment (e.g. recall bias [over/underreporting], social disability bias and issues around comprehension of survey items) [37]. Notwithstanding signi cant logistical constraints, such as substantial cost and high participant burden, forthcoming German physical activity surveillance studies could consider using accelerometers to assess aerobic MVPA and time-use diaries to assess MSE. Nonetheless, self-report assessments are still the most common method used to assess physical activity among large population samples [38]. The low GEDA 2014 response rate (27.2%) is likely to impacted on our MVPA-MSE estimates. It is probable that non-responders are among the least active populations, and despite the steps to provide accurate survey weighting to correct for non-response, we urge that the physical activity estimates reported here be viewed as conservative.
Strengths of this study include the recruitment of a large national-representative sample of German adults. The GEDA 2014 sample (n=24,016) is approximately 20-fold larger than previous German physical activity prevalence surveys [39]. A further strength was the use of the EHIS-PAQ, a standardised physical activity assessment tool assessing both aerobic MVPA and MSE.

Conclusions
Most German adults do not meet the nationally recommended aerobic MVPA-MSE guidelines. These low prevalence levels are concerning from a public health perspective, and highlight that there is a need to provide large-scale physical activity interventions to promote/support both MVPA-MSE uptake and adherence among German adults. Future public health interventions should target those with low socioeconomic status, poor self-rated health, and obese populations. The study protocol was inspected and approved by the 'Federal Commissioner for Data Protection and Freedom of Information in Germany'. Written informed consent was obtained from all participants. Participants were informed about the goals and contents of the study, about privacy and data protection proceedings, and that their participation in the study was voluntary.