Profiling the time-course changes in neuromuscular function and muscle damage over two consecutive tournament stages in elite rugby sevens players

Abstract

Objectives

Many International Rugby Board (IRB) sevens competitions require that two tournament stages are played over consecutive weekends, but the impact this has on player physical performance and recovery is lacking. We examined the influence of two consecutive tournaments on neuromuscular function (NMF) and muscle damage in rugby sevens players.

Design

Ten elite international rugby sevens players completed this observational study over 2 tournaments, separated by 5 days, during the IRB sevens series.

Methods

On the morning of day 1 and 2, of both tournament 1 (T1) and 2 (T2), players performed countermovement jumps (CMJ; jump height [JH]) and capillary blood samples (creatine kinase [CK]) were collected. After the last match of each day, further capillary samples were collected. Additional, CMJ were performed 12 and 60 h post-T1.

Results

Player JH decreased from day 1 to day 2 during T1 (mean ± SD; −6.0 ± 5.4%; P = 0.016), was reduced at 12 (−26.1 ± 5.0%; P < 0.001) and 60 h post-T1 (−7.1 ± 4.8%; P = 0.003) and remained lower, at am day 1 of T2 (−8.0 ± 6.0%; P = 0.007), when compared with day 1 of T1. Player JH was lower on day 1 and 2 of T2, compared with T1 (P < 0.05). CK concentrations were greater than baseline at all time points during each tournament (P < 0.001); no between tournament differences in CK responses existed (P = 0.302).

Conclusions

A single sevens tournament reduces NMF such that players are not fully recovered by the start of the second competition stage, however CK returns to baseline in-between and shows the same pattern across two consecutive tournaments.

Introduction

Rugby union sevens is increasing in popularity, and in 2009 it was added to the 2016 Rio de Janeiro Olympic games. Rugby union sevens competitions differ dramatically from other team sports, including the traditional 15 a-side game, in that they are usually played over a 2 day tournament weekend, with matches consisting of two 7 min halves, with a 2 min half-time interval,¹ on a full dimension rugby union field. A tournament usually consists of 3 group stage matches on the first day, each separated by ∼3 h, and depending on results, up to three on the second day of the tournament. In addition, the international rugby union sevens series (the world professional competition) also requires two stages (i.e. 2 tournaments) to be played on consecutive weekends.

During a sevens match, players can spend ∼75% of the game at heart rates above 80% of maximum² while also covering a total of ∼1581 m, with ∼9% of this distance covered through maximal sprinting, with average sprint distances of ∼18 m²; while in rugby union 15-a-side games this intensity represents ∼2% of the overall game demands.³ These great physiological demands, which are heavily reliant on large contributions from high-intensity, stretch-shortening cycle based movements, combined with physical collisions, may also result in an increased appearance of intramuscular protein/enzymes in the blood,⁴ which are indicative of skeletal muscle damage.⁵ For example, Takashi and colleagues⁴ reported an ∼18% increase in serum creatine kinase (CK) after a single rugby union sevens match, and a further increase (∼42% above baseline) after the second match of the day.

The induction of skeletal muscle damage is also likely to impair neuromuscular function (NMF).⁶ For example, Twist et al.,⁶ reported reductions in NMF (countermovement jump performance) and concomitant increases in CK and muscle soreness 24 and 48 h post-match in professional rugby league players. Similarly, West et al.,⁷ demonstrated that NMF may be reduced for up to 60 h post-match in professional rugby union players. Profiling the recovery time-course after intense contacts sports/training types, e.g.7, 8, 9, is important for coaches, as these data can help inform post-match recovery strategies and training programme design.

Given the intense demands of rugby union sevens competition, and evidence of increases in markers of skeletal muscle damage after just 1 day of competition,⁴ sevens players may be susceptible to reduced NMF over the course of a tournament weekend. Furthermore, as there are occasions where the players may need to compete again 5 days later, there is potential that players may enter a subsequent tournament having not fully recovered from the preceding stage. However, currently there is no information available to confirm or refute these hypotheses. Therefore, the aim of this study was to examine the influence of two consecutive tournament weekends on NMF and muscle damage in elite international rugby union sevens players.