Introduction
The hip and groin region account for approximately 16% of injuries that occur in professional football.1 Adductor-related injuries contribute to 63% of these,2 with prolonged time missed through injury potentially costing premier-league clubs up to £750 000 per club, per season.1
In footballers, reduced hip adduction strength may increase the risk of developing hip and groin injuries by a factor of 4.3 Deficits of approximately 21% have been identified in the eccentric hip adduction strength of footballers who have hip and groin pain.4 Furthermore, eccentric hip adduction (EHAD) strength programmes have demonstrated reductions in hip and groin injuries.5 The ratios between EHAD and eccentric hip abduction (EHAB) may also impact on injury risk.6–8 An EHAD:EHAB ratio between 1.25 and 1.6 is thought to reduce the injury risk to footballers.6–8 However, Mosler et al did not find any association between EHAD:EHAB ratio and injury risk.9 Implementations of injury prevention programme in professional football is low.10 Post exercise muscle soreness has been linked with reduced compliance to prevention protocols.11 This may be a reason why prevention programmes such as the Nordic programme have been limited in professional football.11 Muscle soreness and fatigue require longer recovery and may decrease performance levels in footballers.12 Another challenge with implementing injury prevention programmes is the required dose needed to elicit the desired outcome, and when best to complete such protocols as to not impede on training and matches.
The Copenhagen adduction (CA) protocol is a graduated eccentric training regime that strengthens hip adduction and optimises the EHAD:EHAB ratio.13 Developed by Serner et al,14 the CA exercise is partner assisted, increasing its use in a team environment.14
Differing CA exercises have been shown to increase EHAD strength in footballers of 35.7%,13 8.9%15 and 45.8%.16 A decrease in reported groin problems of 41% has also been seen.5 Muscle soreness was recorded with the median score being 0–2.13 15 16 There were, however, a number of athletes that had higher delayed onset of muscle soreness (DOMS) scores of 7/1013 and 8/1015 in their respective studies. The four studies mentioned earlier were completed using semiprofessional5 or adolescent13 15 16 participants. The minimal dose required and how senior professional footballers would respond to a CA exercise are still unknown. A modified progressive Copenhagen adduction (MPCA) programme starting with isometric muscle contractions and progressing to a full CA exercise has been designed to reduce the risk of DOMS and to assess if a reduced training dose negatively affects senior professional footballers.
Football staff commonly express concerns regarding injury prevention strategies, decreasing the coaching time, and training load the players can complete due to reported increased muscle soreness and fatigue.11
Therefore, a gap exists for an MPCA exercise that reduces comparative postexercise muscle soreness while maintaining the increases in strength, and therefore prevention of injury, in senior professional footballers.
Therefore, the aims of this study were
To determine the effect of an MPCA exercise on the EHAD strength and to review the EHAD:EHAB strength ratio in senior professional footballers.
To measure the level of post exercise muscle soreness in professional footballers who undertake the MPCA exercise.