A cross-sectional study of the relationship between cortical bone and high-impact activity in young adult males and females.
BACKGROUND
The factors that govern skeletal responses to physical activity remain poorly understood.


OBJECTIVE
The aim of this study was to investigate whether gender or fat mass influences relationships between cortical bone and physical activity, after partitioning accelerometer outputs into low (0.5-2.1 g), medium (2.1-4.2 g), or high (>4.2 g) impacts, where g represents gravitational force.


METHODS
We conducted a cross-sectional analysis in participants from the Avon Longitudinal Study of Parents and Children.


METHODS
We studied 675 adolescents (272 boys; mean age, 17.7 yr).


METHODS
We measured cortical bone parameters from peripheral quantitative computed tomography scans of the mid-tibia, adjusted for height, fat mass, and lean mass.


RESULTS
High-impact activity was positively associated with periosteal circumference (PC) in males but not females [coefficients (95% confidence intervals), 0.054 (0.007, 0.100) and 0.07 (-0.028, 0.041), respectively; showing sd change per doubling in activity]. There was also weak evidence that medium impacts were positively related to PC in males but not females (P=0.03 for gender interaction). On stratifying by fat mass, the positive relationship between high-impact activity and PC was greatest in those with the highest fat mass [high impact vs. PC in males, 0.01 (-0.064, 0.085), 0.045 (-0.040, 0.131), 0.098 (0.012, 0.185), for lower, middle, and upper fat tertiles, respectively; high impact vs. PC in females, -0.041 (-0.101, 0.020), -0.028 (-0.077, 0.022), 0.082 (0.015, 0.148), P=0.01 for fat mass interaction]. Similar findings were observed for strength parameters, cross-sectional moment of inertia, and strength-strain index.


CONCLUSIONS
In late adolescence, associations between high-impact activity and PC are attenuated by female gender and low body fat, suggesting that the skeletal response to high-impact activity is particularly reduced in young women with low fat mass.
Musculoskeletal Research Unit, School of Clinical Sciences, University of Bristol, Avon Orthopaedic Centre, Southmead Hospital, Bristol BS10 5NB, United Kingdom.
K
K
Deere
A
A
Sayers
J
J
Rittweger
J H
JH
Tobias
D061725:Accelerometry; D050154:Adiposity / Q000502:physiology*; D000293:Adolescent; D015519:Bone Density / Q000502:physiology; D003430:Cross-Sectional Studies; D005260:Female; D006112:Gravitation; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D010521:Periosteum / Q000000981:diagnostic imaging / Q000502:physiology*; D012044:Regression Analysis; D012727:Sex Characteristics; D013314:Stress, Mechanical; D013977:Tibia / Q000000981:diagnostic imaging / Q000502:physiology*; D014057:Tomography, X-Ray Computed