Stretch-shorten cycle compared with isometric preload: contributions to enhanced muscular performance

Abstract

To isolate any difference muscular contraction history may have on concentric work output, 40 trained male subjects performed three separate isokinetic concentric squats that involved differing contraction histories, 1) a concentric-only (CO) squat, 2) a concentric squat preceded by an isometric preload (IS), and 3) a stretch-shorten cycle (SSC) squat. Over the first 300 ms of the concentric movement, work output for both the SSC and IS conditions was significantly greater (154.8 +/- 39.8 and 147.9 +/- 34.7 J, respectively; P < 0.001) compared with the CO squat (129.7 +/- 34.4 J). In addition, work output after the SSC test over the first 300 ms was also significantly larger than that for the corresponding period after the IS protocol (P < 0.05). There was no difference in normalized, integrated electromyogram among any of the conditions. It was concluded that concentric performance enhancement derived from a preceding stretch of the muscle-tendon complex was largely due to the attainment of a higher active muscle state before the start of the concentric movement. However, it was also hypothesized that contractile element potentiation was a significant contributor to stretch-induced muscular performance under these conditions.

Muscle Power Output Properties Using the Stretch-shortening Cycle of the Upper Limb and Their Relationships with a One-Repetition Maximum Bench Press

“…This suggests that there is a negative counterbalancing effect mitigating the positive effect acquired in the first half of the main movement phase. It was reported also in previous studies (Cavagna et al, 1968;Takamatsu et al, 1991;Walshe et al, 1998) that the effect of SSC is markedly in the first half of concentric contraction.…”

The Effect of Accentuated Eccentric Load on Jump Kinetics in High-Performance Volleyball Players

“…As a muscle performs the eccentric action in any stretch-shortening cycle (SSC), the agonist muscles achieve a preparatory active state with a portion of actin-myosin cross-bridges to be attached prior to the concentric phase of the movement. [14,17] In this study, the eccentric force was greater than normal due to the accentuated eccentric load. In order to accommodate the larger forces in the eccentric action, a greater number of cross-bridges would conceivably occur in the AEBJ condition in comparison to the BJ condition.…”

“…[11,14] A possible contributing neurogenic mechanism for the acute enhancement in kinetic values observed in this study is the increase in neural stimulation that may have been provided by the accentuated eccentric load [15]. The extra load could produce a greater stretch of the intrafusal muscle fibres, which would promote greater stimulation of the associated motor neurons, resulting in greater than normal afferent nerve impulses to the central nervous system.…”

Eccentric Muscle Contractions: Their Contribution to Injury, Prevention, Rehabilitation, and Sport

“…In all likelihood, the increased power of shortening is a combination of both. 173 The ability to recover elastic strain energy is apparently energetically so advantageous that the most economical stride frequency in running may be set by this key property alone. 59,165 Apart from the role of tendons and collagen in energy storage, the muscle itself stores and recovers elastic strain energy, as elastic strain energy can occur in the absence of tendons.…”

“…In fact, the ability to produce high forces with eccentric contractions should perhaps more properly be perceived as a protective muscle adaptation and a stimulus for beneficial muscle (and tendon) responses, rather than as a common cause of damage. 21,64,115,173,177 Many have called for the use of chronic eccentric exercise in the preventative care or rehabilitation of patients. 49,86,110,111,115,116,140,146 In this commentary we explore how muscles adapt both structurally and functionally to chronic high-force eccentric lengthening contractions and how this adaptation may help (1) to prevent musculoskeletal injury, (2) to improve sport performance, and (3) to overcome musculoskeletal impairments.…”