A Comparison of Two Stretching Modalities on Lower-Limb Range of Motion Measurements in Recreational Dancers

Abstract

Wyon, M, Felton, L, and Galloway, S. A comparison of two stretching modalities on lower-limb range of motion measurements in recreational dancers. J Strength Cond Res 23(7): 2144-2148, 2009-Most stretching techniques are designed to place a “stress” on the musculoskeletal unit that will increase its resting length and range of motion (ROM). Twenty-four adolescent dancers participated in a 6-week intervention program that compared low-intensity stretching (Microstretching) with moderate-intensity static stretching on active and passive ranges of motion. Microstretching is a new modality that reduces the possibility of the parasympathetic system being activated. Repeated measures analysis indicated changes in ROM over the intervention period (p < 0.05), with the Microstretching group demonstrating greater increases in passive and active ROM than the static stretch group (p < 0.01); there was no noted bilateral differences in ROM. The results from this study agree with past studies that have found that stretching increases the compliance of any given muscle and therefore increases the range of motion. One main finding of the present study was that throughout a 6-week training program very-low-intensity stretching had a greater positive effect on lower-limb ROM than moderate-intensity static stretching. The most interesting aspect of the study was the greater increase in active ROM compared to passive ROM by the Microstretching group. This suggests that adaptation has occurred within the muscle itself to a greater extent than in structures of the hip joint. Practical application for this technique suggests it is beneficial as a postexercise modality that potentially has a restorative component.

Introduction

Dance, and some aesthetic sports such as rhythmic gymnastics, requires its practitioners to possess significant ranges of motion (ROM), particularly within the lower limb (⁸). Unlike most aesthetic sports, the dancer requires the range of motion to be both dynamic and active; classical ballet is a good example of this, where the female dancer aims to be able to kick her leg through a range of 170 degrees (grande battement) and to place and hold the limb in the same position in a controlled manner (développé) (⁹). This ability is often required in the frontal and sagittal planes and to a lesser range to the rear. A number of studies have linked flexibility to increased injury risk in this population (^3,23,29) and a number of studies have started using intervention strategies to increase active ROM (^1,7,9,20,28).

Static stretching has become the most widely used method for increasing ROM because of the simplicity of execution and reduced potential for tissue trauma (^4,24). It challenges the actin-myosin cross bridge and collagen integrity, thereby stimulating lengthening of the inert structures of the muscle (^19,25), which in turn increases the resting length of the muscle. Muscle by nature is elastic, whereas tendons and ligaments are inelastic (¹⁴); stretching routines therefore need to cause permanent changes in the former rather than the latter. Apostolopoulos (²) suggests that most stretching protocols activate the parasympathetic system causing the muscle to contract to protect itself, therefore moving the stretch stress from the muscle fibers to the myo-tendon junction. This may cause microtrauma and the build-up of scar tissue at this junction (²), increasing the susceptibility to injury at this intersection (²²).

His suggested flexibility routine is based on 2 principles; the first principle comprises frequency, intensity, and duration, and the second comprises stability, balance, and control (SBC), a principle developed by Apostolopoulos (¹). Within this context he suggested that the stretch intensity should be reduced to 30%, from the more commonly recommended 80%, and that the participant should be as stable as possible.

The aim of this study was to examine the affect of low-intensity and moderate-intensity 6-week stretching intervention on active and passive ranges of motion in a recreational dance population. It was hypothesized that a low-intensity stretching intervention would cause greater increases in active and passive ROM than moderate-intensity stretching.

Methodology

Experimental Approach to the Problem

This study was designed to investigate the different changes in active and passive ranges of motion caused by low- and moderate-intensity stretching interventions. Little research has been carried out on the effects of different stretch intensities on limb range of motion with previous research mainly focusing on the optimal time stretches should be held (^1,5,18,19,21) and the frequency of stretching (^6,27).

The 2 groups carried out a series of 5 lower body stretches on a daily basis for 6 weeks. The experimental group held their stretches at a low intensity, whereas the control group maintained moderate-intensity stretches for the intervention. Active and passive hip ROM were measured in the sagittal plane before and after the 6-week intervention period and the data were analyzed.

Participants

Twenty-four adolescent recreational dance students volunteered for the study (14 years of age ± 2.4; 49 ± 8.1 kg; 148.7 ± 15.5 cm). They were presently undertaking 3 to 4 dance classes a week, each mainly in jazz and ballet genres, and had danced for 7 to 10 years. Because the participants were younger than 16 years old, parental/guardian consent was required before involvement was allowed. Ethical approval for the study was given by the Research Centre for Sport, Exercise and Performance at the University of Wolverhampton.

Procedures

In clinical practice, the goniometer has been used to measure ROM; however, there is no universally accepted standard device for measuring hip ROM (¹⁷). Wyon (³⁰) noted that the use of the sit and reach test is pointless within the dance population and therefore the use of photography is recommended; this allowed dance-specific ranges of movement to be assessed. Both active and passive hip ROM were measured in the sagittal plane before and after the 6-week intervention period (Figure 1). Markers were placed on each participant on the medial malleolus and anterior aspect of the hip joint of each leg and the bellybutton. For passive ROM the participant, standing unsupported, lifts the test leg with the hand as high as possible; care must be taken that the hips remain in a neutral position and the leg is not internally rotated before the photograph is taken. The active ROM test is développé when the hip flexors are used to move the limb through its ROM rather than an external force (³⁰). All participants carried out their own individual warm-up prior to data collection, and the greatest ROM from 3 trials was recorded.

Figure 1: Active and passive ranges of motion in the hip's sagittal plane.

SiliconCOACH software was used to analyze dancers' ROMs and allowed both absolute and corrective ROM angles to be measured. Absolute ROM was calculated as the angle between the 2 malleoli and the hip marker of the stance leg. Corrected ROM took account of hip lift in the measured leg by calculating the angle between the 2 hip markers and the malleolus marker of the test leg. Data were analyzed using MANOVA (multivariate analysis of variance) and repeated measures ANOVA using SPSS.v.13. The alpha level was set at a minimum of 95%.

Intervention

The experimental (n = 14) and control (n = 10) groups carried out a series of 5 lower-body stretches on a daily basis for 6 weeks. The experimental group followed protocols from recognized Microstretching materials (²); on nontraining days the program was completed at the dancers' convenience; on training days it was completed 2 hours after exercise had finished under guidelines set by Apostolopoulos (²). The stretches are completed at an intensity of 30% to 40%, whereby 100% equal to pain and thereby inducing a relaxed state within the individual and the specific muscle, and are held for 1 minute. The program is repeated 3 times. The control group mimicked the frequency and duration of the stretches while maintaining the intensity of the stretch at 80%.

Results

Repeated measures analysis indicated changes in ROM over the intervention period (F_1,176 = 5.064; p < 0.05), with the experimental group demonstrating greater increases in passive and active ROM than the control group (F_1,176 = 8.581; p < 0.01) (Figure 2 and Table 1); there were no noted differences in ROM between the sides.

Table 1: Absolute active and passive ROM pre- and postintervention.

Figure 2: Absolute ROM pre- and postintervention.

This also was reflected in the absolute and corrected ROMs (F_1,176 = 3.502; p < 0.06). Further analysis noted significant differences between the groups in the change in ROM between pre- and postintervention (difference), F_1,191 = 5.084; p < 0.01 and in the changes in ROM (difference) between active and passive ROM, F_1,191 = 11.303; p < 0.01 (Figure 3 and Table 2).

Table 2: Corrected active and passive ROM pre- and postintervention.

Figure 3: Corrected ROM pre- and postintervention.

Discussion

Previous research has shown that there are conflicting findings in the area of stretching. Comparison and subsequent conclusions are difficult because of the lack of consistency in the selection of stretching methods used and whether active or passive movement is assessed. Promoting stretching appears to be based mainly on subjective evidence, indicated by studies investigating the effect of stretching on the muscle-tendon unit (^10,12). The results from this study agree with past studies that have found that stretching increases the compliance of any given muscle and therefore increases the range of motion (^6,15,29). The main findings of the present study were that throughout a 6-week training program the intervention of Microstretching had a positive effect on lower-limb ROM.

Within this study both groups increased their passive and active ROMs, although the Microstretching group had the greater improvements in both active and passive ROMs. Both groups recorded greater increases in active rather than passive ROM. Part of this is a result of the anatomic makeup of the hip joint; the maximum abduction in the hip joint alone is 45 degrees (¹³). When the leg is abducted beyond 50 degrees, the pelvis and the spine compensate and the dancer rotates the hip so it no longer is abducting but flexing in another plane (¹⁶). Consequently, corrected angles and absolute angles were taken to see the differences that could result from compensatory techniques that dancers use to get the appearance of extra ROM. Data reported that absolute ROMs increased to a greater extent than corrected, indicating that compensatory techniques were used by participants.

The most interesting aspect of the study was the greater increase in active ROM compared to passive ROM by the intervention group; this was evident in both absolute and corrected ROMs. This suggests that adaptation has occurred within the muscle itself to a greater extent than structures of the hip joint. This gives credence to Apostolopoulos's theory (²) that the specified low intensity and positioning of the stretches allows adaptation to occur within the muscle structure by depressing the response of the sympathetic nervous system and dampening the muscle spindles and Golgi tendon organ. It also could be hypothesized that the intervention group had improved the reciprocal inhibition within the hamstring muscle group, thereby allowing greater ROM through reduced resistance to hip flexor action. Apostolopoulos (²) implies that when an individual carries out Microstretching training properly, the integrity of the connective tissue and muscle is maintained and the exercisers can develop a “flexibility reserve.” This, according to Apostolopoulos (²), is the development and storage of an increased ROM in the musculoskeletal system that enhances performance by allowing movements to be executed without excessive tension, decreasing the resistance of the extended muscles and serving as a safeguard against injury. However, because Apostolopoulos has failed to produce clinical evidence-based research into the process and only suggested why and how Microstretching works based on assumptions using physiological facts and knowledge into the mechanisms of the technique, further in-depth research is required on claims of significantly decreasing healing times and scarring in muscle tissue.

In conclusion, in the present study Microstretching has been shown to develop a greater range of motion in the hip joint than static stretching over a 6-week intervention period. The greatest increases were noted for active ROM, suggesting that the adaptation occurred within the musculo-tendon unit rather than the structures of the joint capsule.

Practical Applications

The utilization of Microstretching as part of an athlete's/dancer's regimen seems beneficial, although the present study has not answered some of Apostolopoulos's other claims.² The exercises should be carried out 2 hours posttraining with an emphasis on body stability and low-intensity exertion.