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Cardiorespiratory fitness levels and associations with physical activity and body composition in young South African adults from Soweto

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ABSTRACT

Background: This observational study aims to describe fitness, and objectively measured physical activity levels and patterns in 409 young black South African adults (aged 19–20 years) from Soweto, as well as to examine associations between physical activity, fitness and BMI.

Methods: A sub-maximal ramped step test was used to obtain an estimate of maximal oxygen uptake (VO2max). Physical activity was measured using ActiGraph (GT1M) for 7 days in 256 participants. Time spent in sedentary (<100 counts per minute (cpm)), moderate (2020–5998 cpm) and vigorous (≥5999 cpm) intensity activity was calculated, and 90% of participants were considered active. Data are presented as mean(CI) or median(CI).

Results: Overweight and obesity was more prevalent in females than males (35% vs 8%, p < 0.001). Males had a higher VO2max than females (41.9(41, 43) vs 32.6(32, 33)mlO2/kg/min, p < 0.001); spent more time in moderate to vigorous intensity physical activity (MVPA) (83(80, 94) vs 43(38, 45)min/day, p < 0.001), and less time in sedentary behaviours (541(541, 567) vs 575(568, 597)min/day, p < 0.01). Sedentary time was not associated with VO2max, however BMI was inversely associated, and MVPA was positively associated, with VO2max (both p < 0.001).

Conclusions: The majority of young South African adults in this study were sufficiently active, and higher MVPA was associated with fitness. However, the high level of sedentary behaviour in this population is of concern and may be contributing to the increasing prevalence of overweight and obesity in this population. Young South African females are at greatest risk for decreased cardiovascular fitness and should be the focus for future interventions.

Electronic supplementary material: The online version of this article (doi:10.1186/s12889-017-4212-0) contains supplementary material, which is available to authorized users.

No MeSH data available.


Proposed bidirectional relationship between sedentary time, physical activity, BMI and fitness
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Fig3: Proposed bidirectional relationship between sedentary time, physical activity, BMI and fitness

Mentions: This high sedentary time and low amounts of vigorous intensity activity, in combination with a high prevalence of overweight and obesity; and the relationships with fitness levels puts these young adults at risk of future cardiometabolic disease. This relationship is most likely bidirectional, where high levels of sedentary behaviour and low fitness results in excess adiposity, thereby increasing BMI. Increased adiposity likely results in further increases in sedentary time, potentially at the expense of moderate and vigorous intensity activity and lower fitness (illustrated in Fig. 3). This vicious cycle of deleterious effects requires intervention, seemingly directed at increasing MVPA; and decreasing BMI and sedentary time, which may allow for improvements in fitness and thus cardiometabolic health. Particular focus should be placed on targeting young female adults, who are at increased risk due to their lower physical activity and fitness levels, higher sedentary time, and high prevalence of overweight and obesity. Considerations of the population and gender specific barriers and factors that could affect interventions should also be made [29, 30]. The findings of this study highlight the importance of increasing MVPA for improvements in fitness; and previous studies have also shown increases in fitness in relation to increases in physical activity (particularly vigorous intensity activity) in populations of similar ages [31, 32]. However, the importance of decreasing sedentary time should not be overlooked. In conjunction with walking for transport, which is already common in this population but tends to be performed at lower intensities, young South African women should also be encouraged to participate in structured, high intensity physical activity on most days of the week, and to reduce sedentary time as much as possible. Potentially, this physical activity should be accumulated in bouts of 10 min of more in order to confer maximum beneficial effects on body composition, thus allowing for improved fitness.Fig. 3.


Cardiorespiratory fitness levels and associations with physical activity and body composition in young South African adults from Soweto
Proposed bidirectional relationship between sedentary time, physical activity, BMI and fitness
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5382390&req=5

Fig3: Proposed bidirectional relationship between sedentary time, physical activity, BMI and fitness
Mentions: This high sedentary time and low amounts of vigorous intensity activity, in combination with a high prevalence of overweight and obesity; and the relationships with fitness levels puts these young adults at risk of future cardiometabolic disease. This relationship is most likely bidirectional, where high levels of sedentary behaviour and low fitness results in excess adiposity, thereby increasing BMI. Increased adiposity likely results in further increases in sedentary time, potentially at the expense of moderate and vigorous intensity activity and lower fitness (illustrated in Fig. 3). This vicious cycle of deleterious effects requires intervention, seemingly directed at increasing MVPA; and decreasing BMI and sedentary time, which may allow for improvements in fitness and thus cardiometabolic health. Particular focus should be placed on targeting young female adults, who are at increased risk due to their lower physical activity and fitness levels, higher sedentary time, and high prevalence of overweight and obesity. Considerations of the population and gender specific barriers and factors that could affect interventions should also be made [29, 30]. The findings of this study highlight the importance of increasing MVPA for improvements in fitness; and previous studies have also shown increases in fitness in relation to increases in physical activity (particularly vigorous intensity activity) in populations of similar ages [31, 32]. However, the importance of decreasing sedentary time should not be overlooked. In conjunction with walking for transport, which is already common in this population but tends to be performed at lower intensities, young South African women should also be encouraged to participate in structured, high intensity physical activity on most days of the week, and to reduce sedentary time as much as possible. Potentially, this physical activity should be accumulated in bouts of 10 min of more in order to confer maximum beneficial effects on body composition, thus allowing for improved fitness.Fig. 3.

View Article: PubMed Central - PubMed

ABSTRACT

Background: This observational study aims to describe fitness, and objectively measured physical activity levels and patterns in 409 young black South African adults (aged 19–20 years) from Soweto, as well as to examine associations between physical activity, fitness and BMI.

Methods: A sub-maximal ramped step test was used to obtain an estimate of maximal oxygen uptake (VO2max). Physical activity was measured using ActiGraph (GT1M) for 7 days in 256 participants. Time spent in sedentary (<100 counts per minute (cpm)), moderate (2020–5998 cpm) and vigorous (≥5999 cpm) intensity activity was calculated, and 90% of participants were considered active. Data are presented as mean(CI) or median(CI).

Results: Overweight and obesity was more prevalent in females than males (35% vs 8%, p < 0.001). Males had a higher VO2max than females (41.9(41, 43) vs 32.6(32, 33)mlO2/kg/min, p < 0.001); spent more time in moderate to vigorous intensity physical activity (MVPA) (83(80, 94) vs 43(38, 45)min/day, p < 0.001), and less time in sedentary behaviours (541(541, 567) vs 575(568, 597)min/day, p < 0.01). Sedentary time was not associated with VO2max, however BMI was inversely associated, and MVPA was positively associated, with VO2max (both p < 0.001).

Conclusions: The majority of young South African adults in this study were sufficiently active, and higher MVPA was associated with fitness. However, the high level of sedentary behaviour in this population is of concern and may be contributing to the increasing prevalence of overweight and obesity in this population. Young South African females are at greatest risk for decreased cardiovascular fitness and should be the focus for future interventions.

Electronic supplementary material: The online version of this article (doi:10.1186/s12889-017-4212-0) contains supplementary material, which is available to authorized users.

No MeSH data available.