The external validity of a novel contract-relax stretching technique on knee flexor range of motion.

Anthony D Kay,Joshua Dixon,Anthony J Blazevich,Liam D Bligh

doi:10.1111/sms.13554

Abstract

IntroductionCompromised joint range of motion (ROM) can negatively affect the capacity to perform activities of daily living in clinical populations. Recently, similar improvements in dorsiflexion ROM were reported following dynamometry‐based contract‐relax (CR) stretching and modified CR stretching technique (stretch‐return‐contract [SRC]) where the contraction phase was performed “off stretch.” As neither the impact of SRC on other muscle groups nor the ecological validity of SRC performed in an applied environment has been tested, the acute effects of both techniques in dynamometry‐ (CRdyna and SRCdyna) and field‐based (CRfield and SRCfield) environments were compared with the hamstring muscle group.MethodsSeventeen participants performed each of the four stretching conditions on separate days in a randomized order. Before and after the stretches, knee extension ROM and passive knee flexor moment were recorded on an isokinetic dynamometer.ResultsSignificant (P < .01) increases in knee extension ROM (4.6‐5.2°) and elastic potential energy storage (12.0%‐23.6%) and decreases in the slope of the passive moment‐angle relation (8.9%‐12.2%) occurred in all conditions. Significant increases in peak passive joint moment were observed after field‐ (14.3%‐14.8%) but not dynamometry‐based (4.6%‐6.6%) stretches. No difference (P > .05) in any measure was found between conditions.ConclusionsThese data confirm the acute efficacy of the SRC technique in the hamstring muscle group and demonstrate its ecological validity in an applied environment in healthy participants. As the field‐based SRC technique was performed without partner assistance, when compared with classical PNF it represents an equally effective and practical stretching paradigm to support athletic and clinical exercise prescription.

Highlights

Compromised joint range of motion (ROM) can negatively affect the capacity to perform activities of daily living in clinical populations
One common method of proprioceptive neuromuscular facilitation (PNF) stretching is the contract‐relax (CR) technique, where repeated cycles of static stretching and intense, often maximal, isometric contractions are performed in a fully stretched position. While this method of stretching has been found to be successful in substantially improving ROM,[11] drawbacks can include the requirement for an assisting partner and the contractions being performed at long muscle lengths, which are often painful and result in greater symptoms of muscle damage.[12,13]
The necessity to stretch the musculature fully prior to initiating these contractions during PNF techniques may be problematic for any population to perform that exhibits muscular hypertonicity, such as spasticity or contracture, where ROM is often compromised and muscles cannot be stretched to their full length.[14]

Summary

Introduction

Compromised joint range of motion (ROM) can negatively affect the capacity to perform activities of daily living in clinical populations. Muscle stretching is both applied and commonly used in both clinical and athletic environments to increase ROM, proprioceptive neuromuscular facilitation (PNF) stretching techniques are often reported as being more effective for promoting both acute and chronic improvements.[8,9,10] One common method of PNF stretching is the contract‐relax (CR) technique, where repeated cycles of static stretching and intense, often maximal, isometric contractions are performed in a fully stretched position. While CR stretching is highly effective and used in clinical populations to achieve rapid increases in ROM, important limitations restrict its more general use

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