Unique environmental effects on physical activity participation: a twin study

Area of Science:

• Behavioral genetics
• Exercise science
• Public health

Background:

• Physical activity offers established health benefits.
• The interplay of genetics and environment in physical activity participation is debated.
• Previous studies suggested significant genetic influence using a lower activity threshold.

Purpose of the Study:

• To investigate how heritability of physical activity participation changes with different activity thresholds.
• To compare genetic and environmental contributions to physical activity using a 60-minute versus a 150-minute weekly activity guideline.

Main Methods:

• Analysis of 1,389 same-sex twin pairs from the University of Washington Twin Registry.
• Utilized tetrachoric correlations and structural equation modeling.
• Assessed physical activity participation using two cut-points: 60 minutes/week and 150 minutes/week.

Main Results:

• Heritability estimates were higher with a 60-minute threshold (45% additive genetics) compared to a 150-minute threshold.
• At the 150-minute threshold, unique environmental factors explained 72% of the variance in physical activity.
• Twin correlations for physical activity were attenuated when using the higher, 150-minute threshold.

Conclusions:

• Environmental factors, particularly unique environmental influences, are the primary drivers of physical activity at levels recommended for health benefits.
• The definition of physical activity thresholds significantly impacts the perceived heritability of participation.