Academic journal article Research Quarterly for Exercise and Sport

Strength Inhibition Following an Acute Stretch Is Not Limited to Novice Stretchers

Academic journal article Research Quarterly for Exercise and Sport

Strength Inhibition Following an Acute Stretch Is Not Limited to Novice Stretchers

Article excerpt

Key words: concentric contraction, flexibility, strength loss, warm-up

Flexibility (joint range of motion) is promoted as an important component of physical fitness (Pollock et al., 1998). It is widely conjectured that increasing flexibility will promote better performances and reduce the incidence of injury (Shellock & Prentice, 1985; Smith, 1994). Consequently, stretching exercises designed to enhance flexibility are regularly included in many athletes' training programs and pre-event warm-up activities (Gleim & McHugh, 1997; Holcomb, 2000).

Notwithstanding the widespread acceptance and use of stretching exercises as a major component of pre-event activities, the purported benefits of stretching on performance and injury prevention have been questioned in several review papers (Gleim & McHugh, 1997; Herbert & Gabriel, 2002; Knudson, 1999; Weldon & Hill, 2003.). In addition, recent research has established an adverse effect of acute static stretching on various different maximal performances. Pre-event stretching has demonstrated an inhibitory effect on maximal force or torque production (Avela, Kyrolainen, & Komi, 1999; Behm, Button, & Butt; 2001; Evetovich, Nauman, Conley, & Todd, 2003; Fowles, Sale, & MacDougall, 2000; Kokkonen, Nelson, & Cornwell, 1998; Nelson, Allen, Cornwell, & Kokkonen, 2001; Nelson, Guillory, Cornwell, & Kokkonen, 2001; Nelson & Kokkonen, 2001), vertical jump performance (Church, Wiggins, Moode, & Crist, 2001; Cornwell, Nelson, Heise, & Sidaway, 2001; McNeal & Sands, 2003; Young & Behm, 2003; Young & Elliott, 2001), and running speed (Nelson, Driscoll, Landin, Young, & Schexnayder, 2005; Siatras, Papadopoulos, Mameletzi, Gerodimos, Kellis, 2003). This paradox between accepted dogma and current research places a difficult decision on coaches and athletes. Do they include flexibility exercises in their pre-event activities and risk the loss of maximal performance, or do they drop the flexibility exercises and increase the risk of injury? To help answer this question, it would be helpful to know if high flexibility has a different influence on force production.

Unfortunately, little information is available about individuals' degree of flexibility in the aforementioned studies. Four of the studies (Church et al., 2001; McNeal & Sands, 2003; Nelson et al., 2005; Siatras et al., 2003) made measurements on competitive athletes. While it is reasonable to assume that competitive athletes perform stretching exercises as part of their training regimen, one cannot be positive that these stretching exercises will routinely yield high flexibility. Moreover, two of the studies (McNeal & Sands, 2003; Siatras et al., 2003) used children whose mean ages were less than 13 years, thus, increasing rather than decreasing the number of possible confounding factors. In addition, the studies reporting the initial flexibility of the individuals tested (Kokkonen et al., 1998; Nelson & Kokkonen, 2001) reported sit-and-reach scores below the 50th percentile of the published norms (for norms, see Hoegar & Hoegar, 1990). Thus, it is possible that the negative impact of stretching is present primarily in individuals who do not regularly engage in stretching activities and/or whose sit-and-reach scores are below the recommended normal percentile (i.e., < 60th percentile for the sit-and-reach).

A case for a differential response between stiff novice stretchers and flexible experienced stretches can be derived from the relationship between motor unit inhibition and the pain reflex. Using electromyographic and twitch interpolation techniques, several researchers determined that stretching causes a decrease in muscle activation and/or motor unit inhibition (Avela et al., 1999; Behm et al., 2001; Fowles et al., 2000). In addition, Magnusson et al. (1997) found a lower stretch tolerance (i.e., the joint angle at which pain is felt) in individuals who had stiffer hamstring muscles and a restricted range of motion on a toe-touch test. …

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