Original researchThe effects of swimming fatigue on shoulder strength, range of motion, joint control, and performance in swimmers
Introduction
Shoulder pain in swimming is a major cause for concern (Beach et al., 1992, Lynch et al., 2010, Tate et al., 2012, Wolf et al., 2009, Yanai et al., 2000), with shoulder injuries occurring in 30%–91% of swimmers (Beach et al., 1992, Tate et al., 2012, Walker et al., 2012, Wolf et al., 2009), and a wide acceptance that shoulder pain is a normal part of swimming (Hibberd & Myers, 2013). This pathology, often characterised as pain following repeated shoulder impingement in swimmers, is described as “swimmers shoulder” [sic] (Kennedy & Hawkins, 1974).
Competitive swimmers practice 6–7 days a week, swim on average between 10,000 m and 14,000 m on each day (Allegrucci et al., 1995, Kluemper et al., 2006, Lynch et al., 2010, Sein et al., 2010), and perform an estimated 16,000–25,000 shoulder rotations during a typical training week (Scovazzo, Browne, Pink, Jobe, & Kerrigan, 1991). With 80% of training time spent on freestyle stroke (Beach et al., 1992), and 90% of the propulsion for this coming from the upper extremities (Barbosa, Fernandes, Keskinen, & Vilas-Boas, 2008), excessive training volumes has been identified as a possible contributing factor to shoulder pathology (Beach et al., 1992; Hibberd & Myers, 2013; Tate et al., 2012, Walker et al., 2012, Wolf et al., 2009). There is a clear relationship between distances trained and shoulder pathology, with swimmers who train for longer distances appearing up to four times as likely to have a shoulder pathology as those who train for less (Beach et al., 1992, Sein et al., 2010, Tate et al., 2012, Walker et al., 2012).
Mechanisms of overuse shoulder injury appear to be related to the inability to maintain optimal posture and movement patterns, resulting in continuous aggravation of susceptible tissues that is worsened under fatigue due to detriments in strength, proprioception, and ROM (Beach et al., 1992, Kluemper et al., 2006, Lynch et al., 2010, Pink and Tibone, 2000, Rupp et al., 1995, Yanai et al., 2000). Competitive swimmers with decreased muscle endurance in external rotation and abduction may be more likely to develop shoulder pathology (Beach et al., 1992). This may be compounded by a protracted shoulder posture further predisposing swimmers to a higher risk of shoulder injuries (Kluemper et al., 2006, Lynch et al., 2010, Pink and Tibone, 2000). If infraspinatus or teres minor are weak, not activating correctly, or are fatigued (Ellenbecker and Cools, 2010, Heyworth and Page, 2011, Heyworth and Williams, 2009, Koester et al., 2005, Michener et al., 2003, Tyler et al., 2000), or if the scapula is already in a forward position, preventing further protraction, (Kluemper et al., 2006, Lynch et al., 2010, Pink and Tibone, 2000), abnormal movement of the gleno-humeral and scapulothoracic joints may predispose an athlete to compression of the sub-acromial space, leading to impingement of supraspinatus tendon and the subacromial bursa (Lynch et al., 2010, Yanai et al., 2000). Shoulder weakness or fatigue in outer range may result in rotator cuff impingement, predominantly of supraspinatus during the abduction and internal rotation that is characteristic of the recovery phase of the freestyle stroke (Yanai et al., 2000).
It is also possible that there is a disparity in the levels of fatigue observed in different muscles. In tennis, Ellenbecker and Roetert (1999) observed that the internal rotator muscles were more fatigue resistant than external rotators. Although this may not directly replicate fatigue in swimming, the relative shift in internal and external rotator strength with fatigue may indicate that internal rotators retain more strength under fatigue than the much smaller external rotators. Indeed, there is some evidence that training the external rotators has a positive effect on reducing shoulder pain in swimmers (Lynch et al., 2010).
As well as detriments to strength, several studies have also identified a detrimental effect of fatigue on proprioception (Lee et al., 2003, Skinner et al., 1986), with as much as a 73% increase in the threshold of detection of movement (Carpenter et al., 1993). This may have implications for the accurate replication of movement patterns that are central to both performance and injury prevention.
These cumulative effects of fatigue on strength, range of motion, and proprioception appear to have a profound impact on swimming performance. Figueiredo, Seifert, Vilas-Boas, and Fernandes (2012) found while testing 10 male competitive swimmers aged 21.6 (±2.4) with 11.00 years of competitive swimming, a significant decrease in biomechanical and coordinative parameters of swimmers occurred under fatigue. Speed decreased by 13.8% (P = 0.00), stroke rate (frequency) by 5.1% (P = 0.00) and stroke length by 6.9% (P = 0.01) with an increase in blood lactate levels of 11.12 mmol−1 (±1.65 mmol−1). This test was able to show biomechanical changes due to fatigue, but only over a very short period of time (96.1 s ± 2.1); this is representative of a race distance but does not mimic the cumulative effects of training. It does however show that swimmers have reduced joint control and proprioception, which may contribute to pathology under fatigue (Carpenter, Blasier, & Pellizzon, 1998).
Previous work has suggested that spatial trajectory and stroke parameters of international swimmers is not easily changed even by the impairments imposed by fatigue, suggesting that stroke rate becomes the most determinant factor of swimming velocity for top level swimmers and not stroke length (Aujouannet et al., 2006, Toussaint et al., 2006). When power output declines, both swim speed and stroke rate decrease, but stroke length remains constant (Toussaint et al., 2006). It appears that the more experienced the swimmer the less deviation in stroke length while under fatigue (Aujouannet et al., 2006, Figueiredo et al., 2012) and may be a factor in the reduced occurrence in shoulder pathology observed in more experienced swimmers (Wolf et al., 2009).
It is therefore hypothesised that interventions that mitigate fatigue and promote the maintenance of optimal posture, proprioception, mobility, and movement patterns during swimming may reduce the chances of shoulder pathology. To identify potentially helpful interventions this study aims to investigate the impact of training induced fatigue on strength, mobility, joint reposition ability, and parameters of performance.
Section snippets
Participants
Seventeen national level youth (8 male, 9 female) swimmers from a North West swimming squad, aged 15.9 years (±1.09), height 174 cm (±7.52 cm), weight 66.06 kg (±8.07 kg), were targeted as part of a convenience sample and invited to participate. The seventeen participants constituted every member of the youth squad. Each participant gave informed consent prior to participation and gave permission for all collected data to be used in this study. All swimmers competed regularly at national level
Lactate
A significant increase (P < 0.001; d = 4.8; r = 0.92) was found in blood lactate, post- 8 × 100 m test, compared to baseline blood lactate (8.81 mmol−1 ± 2.09 vs 1.55 mmol−1 ± 0.42). Blood glucose levels also increased from 5.01 mmol−1 ± 0.91 pre-test to 7.12 mmol−1 ± 1.22 post-test (P < 0.001; d = 1.96; r = 0.7)(Table 1), confirming the high intensity nature of the training session (Anderson et al., 2006, Anderson et al., 2008, Aujouannet et al., 2006, Carr et al., 2011, Figueiredo et al., 2012
Discussion
Following 8 × 100 m training swims, off a 2-min interval at 85% of maximum swim time, several changes were observed. These included a significant reduction in stroke length in both right (13 cm; P < 0.001; d = 1.14; r = 0.5) and left (14 cm; P < 0.001; d = 1.26; r = 0.53), arms, reduced range of motion into external rotation in both right (−5.29°; P < 0.001; d = 0.75; r = 0.35) and left arms (−3.18°; P = 0.04; d = 0.42; r = 0.2), and a 95.3% increase in joint reposition variance on the dominant
Conclusion
This study revealed a reduction in stroke length across both arms and also an arm bias in swimming whereby a greater reduction in both external rotation range and joint position sense was observed in the dominant arm when fatigued. This has highlighted a relationship between fatigue and potential mechanism of shoulder pathology in swimmers. Competitive swimmers may benefit from a shoulder external-rotation strengthening programme that includes inner range external rotation activities, mobility
Conflict of interest statement
None declared.
Ethical approval
Additional individuals who helped in the completion of this study.
Steve Horton and Laura Smith from the University of Salford human Performance laboratory for providing the equipment.
References (38)
- et al.
Individual profiles of spatio-temporal coordination in high intensity swimming
Human Movement Science
(2012) - et al.
Evaluation of shoulder joint position sense in both asymptomatic and rehabilitated professional rugby players and matched controls
Physical Therapy in Sport: official Journal of the Association of Chartered Physiotherapists in Sports Medicine
(2010) - et al.
Shoulder impingement syndrome
American Journal of Medicine
(2005) - et al.
Evaluation of shoulder proprioception following muscle fatigue
Clinical Biomechanics
(2003) - et al.
Anatomical and bio- mechanical mechanisms of subacromial impingement syndrome
Clinical Biomechanics
(2003) - et al.
The painful shoulder in the swimming athlete
The Orthopedic Clinics of North America
(2000) - et al.
Shoulder pain in swimmers: A 12-month prospective cohort study of incidence and risk factors
Physical Therapy in Sport
(2012) - et al.
Shoulder kinesthesia in healthy unilateral athletes participating in upper extremity sports
Journal of Orthopaedic and Sports Physical Therapy
(1995) - et al.
Monitoring seasonal and long-term changes in test performance in elite swimmers
European Journal of Sport Science
(2006) - et al.
Ability of test measures to predict competitive performance in elite swimmers
Journal of Sports Sciences
(2008)