Association of Bone Mineral Measurements With Peak Impact and Sport-Specific Muscle Loads in Elite Youth Artistic Swimmers.

Purpose: Bone mineral measurements and their association with peak impact and sport-specific, persistent muscle loads were examined in 10 elite artistic swimmers age 15-19 years.

Methods: Bone mineral density (BMD) and bone mineral content (BMC) of total body, total body less head, spine, and dominant and nondominant limbs were assessed by dual-energy X-ray absorptiometry. Peak ground-reaction forces of 2 dry jumps (countermovement jump and frog jump) were measured on a force plate. Peak forces applied during in-water exercises (vertical scull, barracuda push, and kick pull) were measured.

Results: On average, artistic swimmers' total-body BMD (1.12 [0.08] g/cm2) was similar to values reported for young swimmers and nonathletic females, and total-body BMC (2359 [399] g) was higher than previously reported in race swimmers. Based on previously published reference curves, 9 out of 10 artistic swimmers had total-body less head BMD and BMC at or above the 90th percentile, with average to above average z scores and height-adjusted z scores for their age. Countermovement jump and frog jump exhibited moderate peak ground-reaction forces (2.61 [0.46] and 1.93 [0.42] N/kg, respectively). In water, greater force was exerted in kick pull (60.4 [4.8] N) compared with vertical skull (45.5 [6.4] N) and barracuda push (40.6 [4.8] N). Bone measurements were correlated with the peak ground-reaction forces exerted in both dry jumps (r = .61-.83, P ≤ .05) and the peak force output of the in-water exercises (r = .63-.80, P ≤ .05).

Conclusion: These results imply robust bone health among artistic swimmers, partially associated with the high muscle forces regularly applied during their sport-specific training that seem to counteract the low-impact nature of the sport.