Physical Activity: the more always the better, or does the context and equilibrium matter?

Purpose
This symposium aims to address an important question: ‘Is more physical activity always better?’ through nuanced considerations of the context of physical activity, such as domains, other physical behaviours and overall lifestyle composition.

Description
Regular physical activity is known to offer a range of health benefits. Recent physical activity guidelines and public health messages tend to focus on the message of ‘move more, sit less’, implying that there are no upper limits to the benefits of physical activity. The latest epidemiological evidence tends to reveal a curve-linear dose-response relationship between physical activity and most health outcomes, suggesting a reduced ‘return on investment’ at the higher end of physical activity. Evolutionary biology evidence suggests that human energy expenditure tends to plateau towards the higher end, indicating an inherent self-regulating mechanism to reach energy equilibrium.

This symposium will start with an overview of the current evidence on physical activity, from epidemiological, physiological and evolutionary biological perspectives. The chair will introduce the concept of energy expenditure equilibrium and the hypothesis of “sweet spots” between activities and recovery. The main presentations will involve three presenters who tackle physical activity in unconventional ways. Rather than examining the total volume of physical activity as done by most epidemiological studies, they considered various intensities of physical activity within the context of other physical behaviours and domains. Presenters also examined a broad range of health outcomes, such as cardiometabolic risk, fitness, pains, and all-cause mortality. Findings from the three presentations share a common theme: more physical activity doesn’t always lead to better health outcomes, and there is a balance to be struck between physical activity and recovery (sedentary behaviour or sleep). The symposium will end with an interactive discussion about the equilibrium between physical activities and recovery, and why the context of the physical activity matters.

This symposium challenges the current paradigm of physical activity and health and has potentially important implications for future physical activity and sedentary behaviour guidelines and health promotion strategies and messaging.

Chair (Name and Affiliation):
Ding (Melody) Ding, PhD, Sydney School of Public Health, Faculty of Medicine and Health, the University of Sydney, Australia

Presenter 1 (Name and Affiliation):
Nidhi Gupta, PhD, Department of Musculoskeletal Disorders and physical work load, National Research Centre for the Working Environment, Copenhagen, Denmark

Presenter 2 (Name and Affiliation):
Stavros Kyriakidis, MSc, Department of Musculoskeletal Disorders and Physical Workload, National Research Centre for the Working Environment, Copenhagen, Denmark and Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark

Presenter 3 (Name and Affiliation):
Sebastien Chastin, PhD, Glasgow Caledonian University, the United Kingdom; Ghent University, Belgium; the University of South Australia, Australia)

Discussant/moderator (Name and Affiliation):
Andreas Holtermann, PhD, Department of Musculoskeletal Disorders and physical work load, National Research Centre for the Working Environment, Copenhagen, Denmark

Presentation 1
Are 24-hour physical behaviour profiles similarly associated with various health outcomes?
Background: Although more moderate-to-vigorous physical activity and less sedentary time individually affect health similarly, their impact may be different when combined with other 24-hour behaviours like standing, light-intensity activity, and sleep. For example, a high-intensity-behaviors profile may improve cardiorespiratory health but when paired with prolonged standing and less sedentary time, it might increase musculoskeletal pain.

Purpose: We explored if 24-hour physical behaviour profiles are consistently associated with various health outcomes.

Methods: 807 workers wore thigh accelerometers and logged sleep and work time for 1-4 days. Using latent profile analyses, individuals were categorized into four distinct physical behaviours profiles; “Chimpanzees” (reference; work; sedentary=197 min, standing=145 min, physical activity=117 min, leisure; physical activity=114 min, standing=121 min, and time in bed=440 min, n = 226), “Lions” (more active work and less active leisure, n=179), “Ants” (more active work and leisure n=244), and “Koalas” (more inactive generally, n=158). Direct measures assessed cardiorespiratory fitness and systolic blood pressure, while back pain and general health were self-reported. Linear and logistic regression models, adjusted for confounders, evaluated the associations between profiles and cardiorespiratory fitness, systolic blood pressure, back pain, and self-rated health.

Results: Compared with Chimpanzees; Ants had similar outcomes but reported higher levels of poor health (p<0.05). Lions were associated with lower cardiorespiratory fitness (p<0.01) but lower systolic blood pressure (p<0.05) and tended (p=0.08) to have less back pain. Koalas were associated with higher systolic blood pressure (p<0.05) and lower cardiorespiratory fitness (p<0.01) but similar self-rated health and back pain.

Conclusion: Our study indicates that the direction of the association of 24-hour behaviour profiles with various outcomes is not consistent. Similar future studies are needed using a prospective study design.

Practical recommendations: Research, guidelines, and communication about 24-hour behaviour profiles may be much more complex than for specific single physical behaviours (e.g. MVPA and sedentary behaviour).

Funding
None declared.

Presentation 2
The “sweet spots” of domain-specific physical activity for preventing back pain: a prospective accelerometer study

Background: High levels of occupational physical activity are associated with back pain while the opposite is the case for leisure-time physical activity. Contrasting effects like this have often been termed the “physical activity paradox”. However, the patterns of occupational and leisure-time physical activity associated with the lowest risk of back pain or (a.k.a, the “sweet spot”, have achieved less attention.

Purpose: We investigated the “sweet spots” (i.e. lowest 5% risk) for back pain from occupational and leisure-time physical activity.

Methods: Three-hundred-ninety-six eldercare workers from 20 nursing homes participated. Physical activity was measured for 4 working days using thigh-worn accelerometry. Back pain intensity was reported monthly on a scale from 0-10 over 1-year. A mixed-effects model regressed occupational and leisure-time physical activity against back pain, adjusted for confounders. The “sweet spots“ associated with the 5% lowest risk for back pain were defined as the occupational composition of sitting, standing, light, and moderate-to-vigorous physical activity and the leisure-time composition of sitting, standing, light, moderate-to-vigorous physical activity and sleep, respectively.

Results: The occupational composition associated with the lowest risk of back pain – the occupational “sweet spot”– consisted of 70.6% sitting, 18.2% standing, 5.4% light physical activity, and 5.8% moderate-to-vigorous physical activity. The leisure-time “sweet spot”– consisted of 18.6% sitting, 26.6% standing, 0.9% light physical activity, 8.6% moderate-to-vigorous physical activity, and 45.3% of sleep.

Conclusions: Compared with the observed occupational composition, the occupational “sweet spot” was towards more sitting and light physical activity time while compared to the observed leisure-time composition, the leisure-time “sweet spot” was towards more standing, moderate-to-vigorous physical activity and sleep time. These clear differences in the “sweet-spots” further support “the physical activity paradox”.

Practical implications: The domain-specific “sweet spots” of physical activity should be considered in future guidelines, recommendations and public health interventions.

Funding
SOSU-pulje

Presentation 3
Striking the right balance: evidence to inform combined physical activity and sedentary behaviour recommendations

Background:
Public health guidelines and policy documents tend to provide recommendations for physical activity and sedentary behaviour separately despite these behaviours being interlinked and co-dependent. In addition. Crucial evidence gaps were identified during the development of the World Health Organization Guidelines on physical activity and sedentary behaviour regarding: (1) the joint association of physical activity and sedentary time with health outcomes and (2) the benefits of light-intensity physical activity.

Purpose: We report alternative ways to present combined recommendations of physical activity and sedentary behaviour for future guidelines and review how current evidence can be used to deliver recommendations for the public to strike the right balance of time between moderate-to-vigorous-intensity physical activity, light-intensity physical activity and sedentary time.

Methods: The study adopts a compositional approach to quantify the dose–response associations between the balance of time spent in physical activity and sedentary time with all-cause mortality. The method is applied directly to the NHANES dataset and in reprocessing the results of previous large cohort studies, meta-analyses and federated analyses.

Results: A similar curvilinear dose relationship between the ratio of time spent in moderate-intensity physical activity/sedentary behaviour and risk of mortality is observed across all cohorts and studies, implying a universal relationship. Public health guidelines should consider adopting recommendations expressed as a balance of over 2.5 minutes of moderate-to-vigorous physical activity per hour of daily sitting, which provides quantitative guidance for moderate-to-vigorous intensity physical activity, light-intensity physical activity and sedentary behaviour in one number.

Conclusions: There is a consistent dose-response between the composition of time spent in moderate-to-vigorous intensity physical activity, light-intensity physical activity and sedentary behaviour and all-cause mortality.

Practical implications: This balance could be a pragmatic way to inform the public in future recommendations.

Funding: None