Conceptual Framework for Strengthening Exercises to Prevent Hamstring Strains
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Conceptual Framework for Strengthening Exercises to Prevent Hamstring Strains Kenny Guex • Gre´goire P. Millet
Ó Springer International Publishing Switzerland 2013
Abstract High-speed running accounts for the majority of hamstring strains in many sports. The terminal swing phase is believed to be the most hazardous as the hamstrings are undergoing an active lengthening contraction in a long muscle length position. Prevention-based strength training mainly focuses on eccentric exercises. However, it appears crucial to integrate other parameters than the contraction type. Therefore, the aim of this study is to present a conceptual framework based on six key parameters (contraction type, load, range of motion, angular velocity, uni-/bilateral exercises, kinetic chain) for the hamstring’s strength exercise for strain prevention. Based on the biomechanical parameters of sprinting, it is proposed to use high-load eccentric contractions. The movement should be performed at a slow to moderate angular velocity and focused at the knee joint, while the hip is kept in a large flexion position in order to reach a greater elongation stress of the hamstrings than in the terminal swing phase. In this way, we believe that, during sprinting, athletes would be better trained to brake the knee extension effectively in the whole range of motion without overstretch of the hamstrings. Finally, based on its functional application, unilateral open kinetic chain should be preferred.
K. Guex (&) Department of Physiotherapy, School of Health Sciences, University of Applied Sciences Western Switzerland, Av. de Beaumont 21, 1011 Lausanne, Switzerland e-mail: [email protected] K. Guex G. P. Millet Department of Physiology, Faculty of Biology and Medicine, ISSUL Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
1 Introduction Hamstring strain injuries have a high prevalence in many sports, including soccer [1, 2], rugby [3, 4], Australian football [5], American football [6], Gaelic football [7], and sprinting [8–11]. High-speed running—the common point between these activities—accounts for the majority of hamstring strains [2, 7, 12, 13]. A good understanding of the biomechanical characteristics responsible for this injury during running is required to optimize the preventive intervention. The running cycle begins when one foot comes in contact with the ground (0 %) and ends when the same foot contacts the ground again (100 %). It is split into two separate phases: the stance and the swing. Toe off marks the end of stance and the beginning of the swing phase. It occurs at *39 % of the running cycle when running [14] and at *22 % when sprinting [15]. Terminal swing and early stance phases have both been proposed to be the main periods for hamstring strain [16, 17]. However, the terminal swing is believed to be the most hazardous for many reasons [2, 18–23]. First, between 75 and 85 % of the running cycle, the hamstrings are undergoing an active lengthening contraction (i.e., eccentric) [19]. The re
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