Do shoulder motor control impairments remain in the year following the last pain episode?

The high dependency of the shoulder complex on muscle control for mid-range stability supports the evidence demonstrating that most ab normal biomechanics and overuse injuries that occur in this region are related to alterations in the function of the scapular-stabilizing muscles (Ciubotariu et al., 2004; Kuhn et al., 1995). Changes in motor control have been claimed to be at the origin, but also in the perpetuation, of the injury/pain if the altered motor strategy or movement leads to excessive loading of tissues. On the other hand, ac cording to the pain adaptation theory, the pain experience is associated with an adaptation in motor behaviour that involves redistribution of ac tivity within and between muscles at multiple levels of the motor system with potential long-term consequences (Hodges et al., 2011). There is evi dence that pain results in gradual decrease in the motor unit discharge rate (Ervilha et al., 2005) via central mechanisms’ adaptation (Thunberg et al., 2002), both in related muscles (Graven-Nielsen et al., 1997) as well as in synergistic and antagonist muscles (Ciubotariu et al., 2004). Specifi cally, studies on shoulder pain demonstrated decreased magnitude and delayed activation of the serratus anterior (SA) (David et al., 2000) and the lower trapezius (LT) muscles (Ludewig et al., 2000) and increased 1 PhD) Escola Superior da Tecnologia de Saúde do Porto, Área Científica de Fisioterapia, Centro de Estudos de Movimento e Atividade Humana, Vila Nova de Gaia, Portugal. 2 (PhD) Escola Superior da Tecnologia de Saúde do Porto, Área Científica de Fisioterapia, Centro de Estudos de Movimento e Atividade Humana, Vila Nova de Gaia, Portugal. 268 Andreia S.P. Sousa and Rui Macedo upper trapezius’ (UT) activity (Ludewig et al., 2000). Also, a bilateral re organization in the coordination among the divisions of the trapezius muscle was demonstrated in response to induced muscle pain (Falla et al., 2007). Despite the known relation between pain and motor control, the treatment of pain is unlikely to be sufficient to restore motor control. Studies involving motor control in low back pain found that many as pects of the motor adaptation persist after the resolution of the pain (MacDonald et al., 2009). To the best of our knowledge, no study evaluat ed shoulder motor control between shoulder pain episodes in tasks in volving mainly concentric activity, but also in tasks involving mainly ex centric activity. Considering that impairments in trunk motor control be tween pain episodes (Ferreira et al., 2004; Hodges et al., 1996) can be re stored with motor relearning strategies (Tsao et al., 2007) and that these changes persist after cessation of training (Tsao et al., 2008), it is im portant to identify shoulder motor control impairments between pain ep isodes to guide effective motor relearning strategies. The purpose of the present study is to evaluate shoulder motor con trol expressed to muscle timings during raised and lowered scaption in subjects with shoulder pain episodes in the last year but currently with out pain.