This study investigated the effect of calcium supplementation in preventing bone stress injuries. Healthy male military recruits (N=1,398) served as subjects, of which 247 were randomly allocated to an experimental group (E) while 1,151 served as a control group (C). For 9 weeks both groups wore the same footwear and had the same physical training program. The baseline dietary intake of calcium in 50 randomly selected subjects of each group was assessed using a 24-hr dietary record. The E group received a daily calcium supplement while the C group did not. Injuries were monitored in all subjects by a panel of doctors who followed specific diagnostic criteria. The mean weekly injury incidence for all overuse injuries, but specifically tibial stress syndrome and stress fractures, was similar in both groups. Mean baseline daily dietary calcium intake was above 800 mg in both subgroups. This study demonstrated that large-scale calcium supplementation (500 nig/ day) beyond usual dietary intake did not influence the risk of developing bone stress injuries during a 9-wk physical training program in these young military recruits.
Martin P. Schwellnus and Gerhard Jordaan
James C. Brown, Caron-Jayne Miller, Michael Posthumus, Martin P. Schwellnus and Malcolm Collins
Endurance running performance is a multifactorial phenotype that is strongly associated with running economy. Sit and reach range of motion (SR ROM) is negatively associated with running economy, suggesting that reduced SR ROM is advantageous for endurance running performance. The COL5A1 gene has been associated with both endurance running performance and SR ROM in separate cohorts. The aim of this study was to investigate whether COL5A1 is associated with ultra-marathon running performance and whether this relationship could be partly explained by prerace SR ROM.
Seventy-two runners (52 male, 20 female) were recruited from the 56 km Two Oceans ultra-marathon and were assessed for prerace SR ROM. The cohort was genotyped for the COL5A1 BsfUI restriction fragment length polymorphism, and race times were collected after the event.
Participants with a TT genotype (341 ± 41 min, N = 21) completed the 56 km Two Oceans ultra-marathon significantly (P = 0.014) faster than participants with TC and CC genotypes (365 ± 39 min, N = 50). The COL5A1 genotype and age accounted for 19% of performance variance. When the cohort was divided into performance and flexibility quadrants, the T allele was significantly (P = 0.044) over-represented within the fast and inflexible quadrant.
The COL5A1 genotype was found to be significantly associated with performance in a 56 km ultra-endurance run. This study confirms previous findings and it furthers our understanding of the relationships among ROM, COL5A1, and endurance running performance. We continue to speculate that the COL5A1 gene alters muscle-tendon stiffness.