The effect of hill sprints and battle ropes with supplementary vitamin D₃ on repeated sprint ability in sub-elite combat sport athletes: a randomised double-blind prospective study

Objectives
The aim of this study is to evaluate if two weeks of concurrent hill sprint and battle rope training induces improvements in repeated sprint ability (RSA) and isometric strength in sub-elite combat sport athletes and if 50000IU·week^-1 vitamin D₃ supplementation produces an ergogenic benefit.

Methods
Fifteen male sub-elite combat sport athletes were recruited (age: 25 ± 4 years: stature: 176 ± 7cm: weight: 78 ± 18kg). Participants undertook baseline lower and upper body RSA testing, handgrip strength testing, isometric hold testing with red blood cell (RBC) lifespan also assessed. Participants were then assigned to consume 50000IU·week^-1 vitamin D₃ (VITD) or 5g·week^-1 olive oil (CON). All participants completed three sessions per week for two weeks of hill sprint and battle rope training with testing repeated at post-intervention prior to statistical analysis with significance set at P<0.05.

Results
RBC lifespan decreased in CON (P<0.001) but not VITD (P=0.757). Lower and upper body peak power decrement decreased in CON (P=0.047 and P<0.001 respectively) with no significant improvement in other RSA markers of performance, handgrip strength or isometric hold ability. (P>0.05). In VITD, lower and upper body average power decrement decreased alongside an improvement in peak and average power held at the end of the RSA test (P<0.05) with lower body best peak power, handgrip strength and isometric hold ability improved (P<0.05).

Conclusion
Two weeks of combined hill sprint and battling rope training improves lower and upper body RSA with 50000IU·week^-1 of vitamin D₃ providing an additive effect to improve RSA and muscle strength while also providing a protective benefit to RBCs.