Editing PNF vs Static Stretching - Essay Example

Purpose: The aim of this investigation was to compare the effectiveness of static stretching and proprioceptive neuromuscular facilitation on hamstring flexibility after a six week stretching programme. Method: Volunteers were randomly assigned to either a static, PNF or control group. Baseline measures for flexibility were taken using a goniometer to measure hip flexion ROM during a straight leg raise, and a modified sit and reach test. Participants performed their stretching protocol 3 times a week for 6 weeks. The static protocol consisted of four different static stretches performed for 30 seconds, the PNF protocol consisted of a contract relax procedure with two 10 second static stretches and a 10 second isometric contraction, the control group resumed no stretching procedure. Straight leg raise and modified sit and reach flexibility measurements were then taken once every week on the same day at the same time. Results: Both static and PNF protocols used in the current investigation were seen as adequate in improving hamstring flexibility. However the PNF technique was shown to produce significantly greater effects than the static group, showing the PNF technique to be the most effective at increasing hamstring flexibility, although whether the changes were due to viscoelastic or neural properties cannot be concluded. Introduction and Literature review Flexibility isan important component in reducing the potential for injury, improving performance during physical activity and sport (Etnyre and Lee, 1988; McCullough, 1990; Taylor et al., 1997; Witvrouw et al., 2004). The hamstring muscle group is susceptible to injury (Funk et al., 2001) during eccentric exercises such as sprinting or jumping, activities which are present in many sports (Kujala et al., 1997). Inadequate muscular flexibility has been cited as one possible cause (Sundquist, 1996; Funk et al., 2001). Muscular flexibility has both mechanical and neurophysiologic components (McHugh et al., 1992). A theorized mechanism by which increases in flexibility and ROM are attained following stretching is the involvement of the viscoelastic properties of the muscle tendon junction (Taylor et al., 1990; Magnusson et al., 1996a; Taylor et al., 1997; Zito et al., 1997; Gribble et al., 1999; De Deyne, 2001), this being the mechanical component of muscular flexibility (McHugh et al., 1992). Viscoelastic behaviour implies a combination of viscous and elastic properties (Sanjeevi, 1982; Taylor et al., 1990; Magnusson et al., 1996a). Elasticity implies that the length change, or deformation, in muscle is directly proportional to the applied force or load (Taylor et al., 1990; Magnusson et al., 1996a; Zito et al., 1997). Viscous properties are characterised as time dependant and rate change dependant, where the rate of deformation is directly proportional to the applied forces (Taylor et al., 1990; Magnusson et al., 1996a; Zito et al., 1997). When a muscle is stretched and held at a constant length gradually there becomes a slow loss of tension, this is known as stress relaxation (Alter, 1996) while the lengthening that occurs when a constant force is applied i.e. a stretch, is known as creep (Alter, 1996). Hysteresis is the variation between the load deformation relationship of loading and unloading (Taylor et al., 1990; Burke et al., 2000), it possibly indicates the viscosity of the muscle. The intramuscular connective tissue that imparts elasticity to muscle tendon, consists of a series elastic and parallel elastic component (Magnusson et al., 1996a; Burke et al., 2000; Youdas et al., 2003). The endomysium is an important elastic component. It transfers force from the contractile component to the tendon and bone in series (Alter, 1996; Magnusson et al., 1996a; Youdas et al., 2003). The perimysium is the principle parallel elastic component. It distributes stress evenly and prevent overstretching (Alter, 1996; Magnusson et al., 1996a; Youdas et al., 2003). The static stretch is a slow, sustained stretch of a particular muscle group, held at maximum ROM, at a point of discomfort for a designated amount of time (Smith 1994; Bandy et al., 1997; Zito et al., 1997; Feland et al., 2001; Stopka et al., 2002; Youdas et al., 2003). During the ballistic stretch the body part is put into motion by bouncing or jerking (Bandy and Irion, 1994; Bandy et al., 1998), through the available ROM until the muscles are stretched to their physiological limits (Bandy et al., 1997). Originally developed by Sherrington (Prentice, 1994), proprioceptive neuromuscular facilitation (PNF) techniques focus on the stimulation of proprioceptors to facilitate or inhibit (Burke, 2000). PNF is a method that is primarily based on the stretch reflex (Magnusson et al., 1996; Chalmers, 2004). The stretch reflex involves two types of receptors, muscle spindles that are sensitive to a change in length and golgi tendon organs that detect changes in tension (Prentice, 1983; Alter, 1996). Many PNF techniques (Feland et al., 2001) often involve isometric contractions of a lengthened muscle, followed by further lengthening, either actively or passively (Bandy et al., 1997; Stopka et al., 2002). Contract-relax (CR) procedures induces stress relaxation by applying tension to the viscoelastic elements during passive stretch (Taylor et al., 1990), causing autogenic inhibition, allowing further muscle elongation via another static stretch (Rowlands et al., 2003). The hold-relax technique is very similar to the CR technique, but instead of being asked to contract the muscle the patient is asked to hold an isometric contraction of the antagonist (hamstrings), allowing autogenic inhibition to occur within the hamstring muscle group (Gribble et al., 1999). Contract-relax agonist contract (CRAC) procedures have an additional contraction of the agonist utilizing additional reflexes in the form of reciprocal inhibition (Rowlands et al., 2003). Reciprocal inhibition is due to the relationship between the agonist and the antagonist muscles (Prentice, 1983). This process is also suspected to occur during the 'hold' of the hold relax technique (Gribble et al., 1999). Measures of flexibility are performed to assess the ability of skeletal muscle and tendon to lengthen (Glein and McHugh, 1997). Goniometric measurement has often been applied to hamstring flexibility (Etnyre and Lee, 1988; Bandy et al., 1997; Gribble et al., 1999. The sit and reach test has been shown to represent moderate validity in measuring hamstring flexibility and has a high reliability (Hui et al., 1999), however it has also been indicated that the sit and reach test does not allow for proportional differences between the legs and arms (Hoeger and Hopkins, 1992). The sit and reach test was modified by sliding measurement scale across the top of the box, instead of it being fixed, allowing for limb length bias (Hoeger and Hopkins, 1992). Findings from Cole et al., (1996) indicate that the use of such a test does eliminate limb-length bias Aim The aim of this investigation was to determine whether there was a significant difference between static and CR PNF stretching methods using goniometry and the modified sit and reach test as flexibility measurements after a six-week stretching programme, which would indicate the most effective method in increasing hamstring flexibility. Method A pilot study was conducted involving a static and PNF procedure (Appendix 1). Experimental Study 24 participants (13 male, 11 female) completed a health history questionnaire, ethical protocol and gave informed consent (Appendix 2). All of them were free of any lower limb and back injuries and were asked not to resume any other stretching routines. They were required to wear shorts and t-shirt and carry out all stretching procedures and flexibility measurements with bare feet. Table 1. Participant characteristics for each stretch group. Stretch group Gender Age (years) (MeanSD) Height (cm) (MeanSD) Weight (kg) (MeanSD) Baseline SLR() (MeanSD) Baseline SR(cm) (MeanSD) Static 4m,4f 25.28.5 1708.8 66.88.1 72.58.2 298.5 PNF 5m,3f 24.86.7 1739.9 66.412.9 73.012.2 259.2 Control 4m,4f 24.06.9 1746.8 67.74.8 74.011.0 299.8 Experimental design The experiment had an independent participant sample design; participants were randomly assigned to one of three groups, a static, PNF, and control group (split equally for gender). The experiment had a repeated measures design with each group of participants completing a familiarisation session, a baseline flexibility measure, six week stretching programme (stretching three times a week) and six flexibility measurements taken on a weekly basis on the same day at the same time. Measuring apparatus Goniometer The goniometer consisted of a transparent plastic; full circle (360) protractor marked off at 1 intervals, with two pivoting movement arms (Appendix 3a) and was used to measure hip flexion ROM during a straight leg raise. With the participant lying supine, the greater trochanter and lateral epicondyle of the right leg was palpated. The goniometer was positioned with the pivoting part on the greater trochanter, with one movement arm running parallel with the femur and lateral epicondyle and the other running parallel with the trunk, with 0 representing neutral in supine (Appendix 3b). The participant then performed a straight leg raise (right leg) until discomfort was felt in the hamstrings, whilst the experimenter made sure the pelvis was fixed and the leg remained straight. The angle of hip flexion was then measured by moving the measurement arm of the goniometer parallel to the femur and lateral epicondyle (Appendix 3c) (Etnyre and Lee, 1988). Modified sit and reach test The box was 30.5 cm high, with a sliding measurement scale from 0-70 cm placed on the top (Appendix 4a). The participant sat with hips, back and head against a wall (90 angle at hip joint) and feet against the box. The participant placed hand over hand and reached out level with the measurement scale, keeping head, back and hips against the wall. The sliding measurement scale was then moved along the top of the box so the zero mark was at the participant's finger tips (Appendix 4b). This established the relative zero point for each individual based on proportional differences in limb lengths. The participant then performed the reach test. The participant reached forward as far as possible whilst keeping the legs straight, the criterion score was the total distance reached (cm)(Appendix 4c)(Hoeger and Hopkins, 1992). Experimental procedure Participants arrived at the experimental room, gave informed consent and completed a health history questionnaire and ethical protocol. Participant's height and weight were taken using a stadio meter and avery scale. Participants were then assigned randomly to and familiarized with, but did not resume, either a static or PNF stretching protocol (Appendix 5a, b, c, d and e) which had to be completed three times a week for six weeks, or a control group. A baseline measurement of flexibility was taken. Participants performed the straight leg raise first (Appendix 3a, b and c), followed by the modified sit and reach procedure (Appendix 4a, b and c). Participants were required to meet up with the examiner 3 times a week to complete their stretches, for 6 weeks. Flexibility measurements were taken once every week on the same day at approximately the same time by the same examiner to reduce error. Stretching Protocol The static protocol (Appendix 5a, b, c and d) consisted of four (Taylor et al., 1990) different static stretches performed with the pelvis in an anterior tilted position (Sullivan et al., 1992) a floor sitting position (Chan et al., 2001) a straight leg raise position (Alter, 1998) and a standing position (Alter, 1997) each performed for 30 seconds. The PNF protocol consisted of a contract-relax procedure (Appendix 5e) (Alter, 1997; Alter, 1998) each repeated four times on each leg (Taylor et al., 1990). The control group did not participate in any stretching procedures. Statistical analysis Firstly the data was checked for normality. The change in flexibility score from baseline was calculated for each week. A two way ANOVA with one repeated measure was conducted on the change in weekly flexibility score from baseline measure for both measurement methods and each stretch group (time, within subject factors, stretch, between subject factors) to examine if any changes found were significant. Significance was accepted when P Read More