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Effects of a lighter discus on shoulder muscle activity in elite throwers, implications for injury prevention

Dinu, D, Slawinski, J, Houel, N and Louis, J Effects of a lighter discus on shoulder muscle activity in elite throwers, implications for injury prevention. International Journal of Sports Physical Therapy. (Accepted)

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Abstract

Background: Performance in discus throw requires high forces and torques generated from the shoulder of the throwing arm, making shoulder muscles at risk of overuse injury. Little is known on muscle activation patterns in elite discus throw.
Hypothesis/Purpose: The purpose of this study was to examine the kinetics and shoulder muscle activation during discus throws by using two discs of different mass. It was hypothesized that the use of a lighter discus would modify the activation of the shoulder musculature compared to a standard discus.
Study design: Case-control laboratory study
Methods: Seven male elite discus throwers performed five throws using a standard discus (STD, 2.0 kg) and five throws using a lighter weight discus (LGT, 1.7 kg). Surface EMG was recorded for the biceps brachii (BB), deltoideus anterior (DA), deltoideus medialis (DM), clavicular head of the pectoralis major (PM), latissimus dorsi (LD), and trapezius medialis (TM). Three-dimensional high-speed video analysis was utilised to record discus speed and identify the different temporal phases of each throw from the preparation phase (P1) to the delivery phase (P5).
Results: The EMG activation of LD lasted longer (p < 0.01) in P1 and was initiated later in P5 with the LGT discus compared to STD. In P5, the EMG intensity of BB decreased (p = 0.02) with LGT (%EMGmax = 50.4 ± 49.6%) compared to STD (64.8 ± 77.9%) and the activation of PM increased (p < 0.01) with LGT (86.2 ± 40.3%) compared to STD (66.2 ± 26.9%). The discus speed at release was increased (p = 0.04) by using the LGT discus (20.62 ± 0.75m.s-1) compared to STD (19.61 ± 0.57m.s-1). The throwing distance was also increased (P < 0.01) with the LGT (43.1 ± 4.3m) discus compared to STD (39.4 ± 3.4m).
Conclusion: A lighter discus could be used by elite athletes in training t 50 o add variability in muscle solicitation and thus limit the overload on certain muscles of the shoulder region. These results may have implications to lower the risk of injury in discus throw. Clinical relevance: The increase in shoulder muscle activity combined with the accelerated forward swing of the throwing arm in P5 may help explain the incidence of muscle and tendon injuries clinically observed in discus throw. Using a lighter discus in training may add variability in muscle activity and motion kinetics to lower the mechanical load on the shoulder and tendons.

Item Type: Article
Subjects: R Medicine > RC Internal medicine > RC1200 Sports Medicine
Divisions: Sport & Exercise Sciences
Publisher: American Academy of Sports Physical Therapy
Date Deposited: 05 Apr 2019 12:05
Last Modified: 05 Apr 2019 12:11
URI: http://researchonline.ljmu.ac.uk/id/eprint/10287

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