Alis Bonsignore

The energy expenditure benefits of reallocating sedentary time with physical activity: a systematic review and meta-analysis

Background We compared direct and daily cumulative energy expenditure (EE) differences associated with reallocating sedentary time to physical activity in adults for meaningful EE changes. Methods Peer-reviewed studies in PubMed, Medline, EMBASE, CINAHL, PsycINFO, Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews were searched from inception to March 2017. Randomized and non-randomized interventions with sedentary time and EE outcomes in adults were included. Study quality was assessed by the National Heart Lung and Blood Institute tool, and summarized using random-effects meta-analysis and meta-regression. Results In total, 26 studies were reviewed, and 24 studies examined by meta-analysis. Reallocating 6-9 h of sedentary time to light-intensity physical activity (LIPA) (standardized mean difference [SMD], 2.501 [CI: 1.204-5.363]) had lower cumulative EE than 6-9 h of combined LIPA and moderate-vigorous intensity physical activity (LIPA and moderate-vigorous physical activity [MVPA]) (SMD, 5.218 [CI: 3.822-6.613]). Reallocating 1 h of MVPA resulted in greater cumulative EE than 3-5 h of LIPA and MVPA, but <6-9 h of LIPA and MVPA. Conclusions Comparable EE can be achieved by different strategies, and promoting MVPA might be effective for those individuals where a combination of MVPA and LIPA is challenging.

Defining lifelong exercise frequency and arterial stiffness changes in older adults: considerations for sex differences and exercise dose

Arterial stiffness parameters measure arterial elastic properties and represent an important determinant of cardiovascular health. The physiological underpinning of arterial stiffness, which has been rightfully popularized given its clinical relevance, requires some basic physiological knowledge. The historical Windkessel model provides a conceptual model for understanding the dampening effects of arterial function. During the cardiac cycle, incident arterial pressure waveforms are distributed centrally from the cardiac system toward peripheral arteries and reflected back toward the cardiac system. The presence of ageing and disease have been widely associated with increased arterial stiffness, such that arterial waveforms are propagated outward and reflected back at a faster rate. This phenomenon can result in the incident and reflective waves merging to cause higher systolic pressures and lower diastolic pressures. Remarkably, the exercise ‘dose–response’ relationship has shown that higher exercise ‘doses’ may reduce arterial stiffness. The extent to which exercise ‘dose’ components of frequency, intensity and duration contribute to reductions in central and peripheral arterial stiffness, however, is not completely understood. Furthermore, there are important distinctions in the modulation of arterial stiffness between individuals, and one thing is clear, sex matters. Most recently, the relationships among arterial stiffness, ageing and exercise ‘dose’ were described in an article in The Journal of Physiology (Shibata et al. 2018). The authors sought to test the hypothesis that high lifelong exercise ‘dose’ (e.g. 4–5 weekly exercise sessions of >30 min in duration) would be associated with a reduction in central arterial stiffness using subjects recruited largely from the Cooper Center Longitudinal Study database (with the exception of Masters athletes who were recruited separately to characterize the highest exercise ‘dose’ quartile). This established longitudinal study offers a unique clinical research advantage in characterizing physical activity and cardiovascular risk given the large sample size (>80,000 individuals) and follow-up period (>40 years). In the current study, older males and females (n = 102, >60 years old) were screened based on medical history, physical examination and detailed exercise training history. Eligible participants had detailed assessments for arterial stiffness (including pulse wave velocity, augmentation index and biological aortic age) and were stratified into four groups based on self-reported lifelong exercise ‘doses’, including: sedentary (0–1 exercise session/week), casual (2–3 exercise sessions/week), committed (4–5 exercise sessions/week) and competitive athletes (6–7 exercise sessions/week). The authors elegantly reported that life-long habitual activity (>25 years) at a frequency of 4–5 times per week was associated with lower central arterial stiffness but not peripheral arterial stiffness, which is reflective of large conduit and small resistance vessel structure, respectfully. To a similar extent, total arterial compliance, blood pressures and cardiac afterload, which are reflective of small resistance vessel function, were improved with even a modest (2–3 sessions per week) amount of lifelong exercise. As a result, the authors concluded that higher lifelong volumes of aerobic exercise may prevent adverse central arterial stiffness common with ageing. The association between lifelong habitual exercise and markers of vascular structure and function provides novel insight for therapeutic interventions to modulate the profound age-related declines in vascular health. The importance of the current study findings cannot be understated, since large epidemiological studies have demonstrated that age-associated declines in vascular function and structure are associated with all-cause and cardiac-related mortality, although it is unknown if the benefits observed in this study are different between men and women. Based on previous evidence, sex differences in response to long-term habitual exercise training in older adults is inconsistent, reporting that older women experience similar responses relative to older men (Endes et al. 2016), or no effect on vascular structure and function (Pierce et al. 2011). This has been attributed largely to sex differences in vascular ageing, the loss of circulating oestrogen following menopause in women and differences in cardiopulmonary fitness. The authors address this and acknowledge that there were no differences between the sedentary and exercise groups in the male/female ratio; however, there were only a small number of women in the exercise groups (i.e. male/female ratio in casual exercises of 18/7; committed exercises 20/5; competitive exercises 17/8), which may limit the generalizability of these results to both men and women. Higher cardiopulmonary fitness observed with increases in frequency of exercise paralleled the increased numbers of males versus females in these cohorts. As such, sex and cardiopulmonary fitness may have interacted and had a direct influence on the study findings. A future comparison between equal numbers of men and women matched on cardiopulmonary fitness may better address the association between habitual exercise and markers of vascular health, particularly if differential doses of habitual exercise are needed to confer the same benefits in older men versus women. Nonetheless, one key difference between these previous data and the current study is life-long participation in exercise compared to shorter durations (i.e. 5 years versus >25 years). Accordingly, this provides both novel and promising insight for favourable intervention to prevent cardiovascular disease if exercise started earlier in life can decrease the signs of vascular ageing in older women. Future research should consider potentially important sex differences when designing such clinical investigations to increase the widespread application of these data. This is especially critical in the design of studies and reporting of data that address important research gaps regarding potential interventions to