Differences in the vertical and horizontal force-velocity profile between academy and senior professional rugby league players, and the implications for strength and speed training.

BACKGROUND: This study compared the vertical and horizontal force-velocity (FV) profile of academy and senior rugby league players. METHODS: Nineteen senior and twenty academy players from one professional club participated in this study. The vertical FV profile was determined using a series of loaded squat jumps (0.4 to 80 kg) with jump height recorded. The horizontal FV profile involved a 30-m over-ground sprint with split times recorded at 5, 10, 15, 20 and 30 m. Theoretical maximal force (F0), velocity (V0) and power (Pmax), optimal F0 and V0, and activity specific variables (e.g., vertical FV imbalance) were determined. RESULTS: Absolute F0 and Pmax from the vertical and horizontal profile were moderately different between groups (standardized mean difference [SMD] = 0.64-1.20, P<0.001-0.026), whilst for V0, differences were small (SMD=0.33-0.41, P=0.149-0.283). Differences in relative F0, Pmax and optimal F0 during both assessments were trivial to moderate (SMD=0.03-0.82, P=0.021-0.907). CONCLUSIONS: These results demonstrate senior and academy players present with different FV profiles and highlight some potential developmental opportunities for senior and academy rugby league players that sport scientists, strength and conditioning and rugby coaches can implement when designing programmes and considering long-term athlete development.

Montmorency tart cherry juice does not reduce markers of muscle soreness, function and inflammation following professional male rugby League match-play.

Rugby League (RL) match-play causes muscle damage, inflammation and symptoms of fatigue. To facilitate recovery, nutritional interventions are often employed, including Montmorency cherry juice (MC). We assessed the effects of MC on recovery following RL match-play in eleven male professional RL players who played in two matches (7-days apart) with MC or placebo (PLB) supplemented for 5-days pre-match, matchday and 2-days post-match. Blood was collected 48h pre-match, half-time, within 30-mins of full-time and 48h post-match to assess Interleukin concentrations (IL-6, -8 -10). Self-reported sleep, fatigue, mood, stress, and muscle-soreness were assessed 24h pre and 24 and 48h post-matches with muscle function assessed 48h pre and 48h post-match. No differences in distance covered (6334 ± 1944 Vs 6596 ± 1776m) and total collisions (28 ± 11 Vs 29 ± 13) were observed between both matches. There was a small albeit significant increase in IL-6, -8 and -10 concentrations pre to post-match in both PLB (IL-6: 0.83 ± 0.92 Vs 2.91 ± 1.40, IL-8: 2.16 ± 1.22 Vs 3.91 ± 1.61 and IL-10: 2.51 ± 2.14 Vs 0.61 ± 0.50 pg.mL-1) and MC groups (IL-6: 0.53 ± 0.53 Vs 2.24 ± 1.73, IL-8: 1.85 ± 0.96 Vs 3.46 ± 1.12 and IL-10: 0.48 ± 0.50 Vs 2.54 ± 2.10 pg.mL-1), although there were no significant differences between groups (P<0.05). Likewise, there was a small but significant increase in muscle soreness (P=0.01) and reduction in CMJ (P=0.003) with no significant differences between groups. No significant changes in sleep, fatigue or mood (P>0.05) were observed pre to post-match or between groups. These data suggest MC does not affect the modest changes observed in cytokine responses and markers of recovery from RL match-play.Keywords: Team Sport, Nutrition, Performance, Recovery.

Development of anthropometric characteristics in professional Rugby League players: Is there too much emphasis on the pre-season period?

Rugby League is a team sport requiring players to experience large impact collisions, thus requiring high amounts of muscle mass. Many players (academy and senior) strive to increase muscle mass during the pre-season, however, quantification of changes during this period have not been thoroughly investigated. We therefore assessed changes in body-composition using Dual X-Ray Absorptiometry (DXA) in eleven academy players over three successive pre-seasons and ninety-three senior players from four different European Super League clubs prior to, and at the end of, a pre-season training period. There was no meaningful change in lean mass of the academy players during any of the pre-season periods (year 1 = 72.3 ± 7.1-73.2 ± 7.2kg; ES 0.05, year 2 = 74.4 ± 6.9-75.5 ± 6.9kg; ES 0.07, year 3 = 75.9 ± 6.7-76.8 ± 6.6kg; ES 0.06) with small changes only occurring over the three-year study period (72.3-75.9kg; ES = 0.22). Senior players showed trivial changes in all characteristics during the pre-season period (total mass = 95.1-95.0kg; ES -0.01, lean mass = 74.6-75.1kg; ES 0.07, fat mass = 13.6-12.9kg; ES -0.17, body fat percentage = 14.8-14.1%; ES -0.19). These data suggest that academy players need time to develop towards profiles congruent with senior players. Moreover, once players reach senior level, body-composition changes are trivial during the pre-season and therefore teams may need to individualise training for players striving to gain muscle mass by reducing other training loads.