Purpose Positive associations have been identified between bone outcomes and accelerometer-derived moderate (MPA) and vigorous (VPA) physical activity (PA) in youth, however, it
remains unclear which intensity is most beneficial. This systematic review aimed to summarise
accelerometer-derived methods used to estimate habitual PA in ...
Purpose Positive associations have been identified between bone outcomes and accelerometer-derived moderate (MPA) and vigorous (VPA) physical activity (PA) in youth, however, it
remains unclear which intensity is most beneficial. This systematic review aimed to summarise
accelerometer-derived methods used to estimate habitual PA in children and adolescents and
determine whether the magnitude of association was consistently stronger for a particular
intensity (MPA/MVPA/VPA).
Methods Observational studies assessing associations between accelerometer-derived MPA
and/or MVPA and VPA with bone outcomes in children and adolescents (≤ 18 years) were
identified in MEDLINE, EMBASE, Web of Science, SPORTDiscus and the Cochrane Central
Register of Controlled Trials. Thirty articles were included (total n=20,613 (10,077 males), 4-
18 years). Chi-square tests determined whether the proportion of significant associations and
strongest within-study associations, differed significantly between intensities.
Results Accelerometer methods were highly variable between studies. Of the 570 associations
analysed, 186 were significant (p<0.05). The proportion of within-study strongest associations
differed by PA intensity (3x2 χ
2=86.6, p<0.001) and was significantly higher for VPA (39%)
compared to MVPA (5%; 2x2 χ
2=55.3, p<0.001) and MPA (9%, 2x2 χ
2=49.1, p<0.001). Conclusion Results indicated a greater benefit of VPA over MPA/MVPA, however, variability
in accelerometer-derived methods used prevents the precise bone-benefitting amount of VPA
from being identified. Long epochs and numerous intensity cut-point definitions mean that
bone-relevant PA has likely been missed or misclassified in this population. Future research
should explore the use of shorter epochs (1s) and identify bone-specific activity intensities,
rather than using pre-defined activity classifications more relevant to cardiovascular health.