Confusion and conflict in assessing the physical activity status of middle-aged men

Abstract

Background: Physical activity (including exercise) is prescribed for health and there are various recommendations that can be used to gauge physical activity status. The objective of the current study was to determine whether twelve commonly-used physical activity recommendations similarly classified middle-aged men as sufficiently active for general health.

Methods and findings: We examined the commonality in the classification of physical activity status between twelve variations of physical activity recommendations for general health in ninety men aged 45-64 years. Physical activity was assessed using synchronised accelerometry and heart rate. Using different guidelines but the same raw data, the proportion of men defined as active ranged from to 11% to 98% for individual recommendations (median 73%, IQR 30% to 87%). There was very poor absolute agreement between the recommendations, with an intraclass correlation coefficient (A,1) of 0.24 (95% CI, 0.15 to 0.34). Only 8% of men met all 12 recommendations and would therefore be unanimously classified as active and only one man failed to meet every recommendation and would therefore be unanimously classified as not sufficiently active. The wide variability in physical activity classification was explained by ostensibly subtle differences between the 12 recommendations for thresholds related to activity volume (time or energy), distribution (e.g., number of days of the week), moderate intensity cut-point (e.g., 3 vs. 4 metabolic equivalents or METs), and duration (including bout length).

Conclusions: Physical activity status varies enormously depending on the physical activity recommendation that is applied and even ostensibly small differences have a major impact. Approximately nine out of every ten men in the present study could be variably described as either active or not sufficiently active. Either the effective dose or prescription that underlies each physical activity recommendation is different or each recommendation is seeking the same prescriptive outcome but with variable success.

Figure 1. The proportion of middle-aged men in this sample who either met or failed to meet each of the 10 recommendations (n = 90).

Figure 2. Ranked individual data for total MET^.min per week (Figure 2a) which is equivalent to the ACSM/AHA² recommendation, PAL (Figure 2b) which is the basis for the IOM¹ recommendation, and average minutes of moderate intensity physical above 3 METs per day, which is the basis for IOM² (Figure 2c).

The horizontal dashed line indicates the threshold identified for each recommendation - every person above this threshold meets each respective recommendation. The shaded columns indicate where this particular subject also met the current ACSM/AHA¹ recommendation (i.e., either 5 days of moderate activity or 3 days of vigorous activity).