You are here: UK Essays » Essays » Physical Education » Proprioceptive Neuromuscular Facilitation

Free Essays - Physical Education Essays

Proprioceptive neuromuscular facilitation, dynamic stretching, and plyometrics: a literature review.

A review of existing literature and research of the three training systems considered in this study assisted in the creation of study parameters and hypothesis.  Specifically, literature on proprioceptive neuromuscular facilitation, dynamic stretching, and plyometrics was reviewed.  There was no literature found that considered or compared all three training systems, although two studies looked at proprioceptive neuromuscular facilitation and dynamic stretching in relation to each other and static stretching (Weerapong, Hume, and Kolt 2004; Bradley, Olsen and Portas 2005).  Specific consideration was given to studies involving strengthening and jumping ability, as opposed to those studies solely measuring range of motion or flexibility.

Explosive power is held to be generated by increased elastic energy stored in the muscle fibres (Geiger 2004).  It is therefore believed that exercise or stretch that increases this elastic energy will result in increased explosive power for that group of target muscles.  In addition, “increases in muscle strength are related to a number of kinematic factors that are important to the movement specificity” (Fowler and Lees 1998, 261).   The type and velocity of muscle contraction, the range of joint angles, and the velocity of joint movement all contribute to explosive power.  In addition, some have concluded the coordination between joint and muscle movement has direct implication for explosive power and strength (Fowler and Lees 1998).  This leans toward plyometrics as the training method, of the three mentioned above, as most likely to increase strength, explosive power, and jump performance.

Proprioceptive neuromuscular facilitation stretching, or PNF, is becoming increasingly popular with both professional and amateur athletes.  PNF was first developed by Margaret Knott, Dorothy Voss, and Dr. Herman Kabat in the late 1940s as a method for rehabilitating and treating patients with partial paralysis or muscle control loss.  Typical patients suffered from polio, cerebral palsy, multiple sclerosis, or similarly disabling conditions (Stone 2000).  It was designed to increase flexibility, coordination and strength, and as it is an effective method for increase in all three areas, soon was incorporated in many mainstream athletic training programmes (Grieco 2002).  

In the PNF training system, a combination of stretches and isometric muscle contractions result in fairly rapid stretch.  Typical patterns of these combinations are hold-relax, contract-relax, and slow-reversal-hold (Weerapong, Hume, and Kolt 2004).  In the contract-relax pattern, for example, the stretcher begins by moving slowly until a comfortable stretch of the target muscle group is achieved.  This position is held briefly, usually fifteen to thirty seconds.  The position may be achieved through static-active flexibility stretches, where the stretcher maintains the position independently, or static-passive flexibility stretches, where the stretcher maintains the position with the assistance of another of his or her limbs, a partner, or a fixed object such as a wall or barre (Alter 1988).  The stretcher, keeping the target muscle group at this place of stretch, then isometrically contracts the target muscle group to deepen the stretch.  This is typically followed by a slight furthering of the stretch, again holding it for fifteen to thirty seconds (Grieco 2002). 

The first stretch elongates the muscle fibres and connective tissues, and the stretch is then held to allow the muscle spindles to adjust to the new increased muscle length (Carter et al 2000).  As the tissues are held at the new length, the force on the muscle at this length declines gradually.  This is called the stress relaxation response (Magnusson et al 1996).  The tissue gradually deforms to the new length, allowing the muscle spindles’ stretch receptors to adjust to the new, elongated muscle, evidencing ‘creep.’ (Weerapong, Hume, and Kolt 2004; Greico 2002).  The following isometric contraction, usually lasting six to ten seconds, serves to activate the golgi tendon organ, which further relaxes the muscle and allows additional stretch (Carter et al 2000; Stopka et al 2002).  PNF stretching results in increasing range of motion, and allows the muscle to develop tension but does not shorten it.  “The resulting gains in stretching ability are caused by autogenic inhibition; the contraction of the antagonist muscle causes relaxation of the agonist, resulting in an increase in stretching ability” (Stopka et al 2002, 23). 

While PNF stretching has been shown to be effective in muscle elongation and increased flexibility.  “Researchers agree that proprioceptive neuromuscular facilitation (PNF) stretching techniques elicit maximal improvements in joint range of motion in the shortest amount of time (Carter et al 2000, 270).  However, PNF has not been documented to increase strength or explosive power in the short term.  Young and Elliott (2001), in a study male athletes, found that PNF stretching of the contract-relax pattern reduced mean drop jump performance by 3.2% and mean squat jump results by 3.3%, although neither finding was concluded to be statistically significant.  They additionally concluded, “stretching with PNF and MVC of the leg extensor muscles had no significant effect on concentric of SSC muscle performance” (279).  Similarly Fowles and Sale (1997) found that thirty minutes of similar stretching reduced strength by as much as nine percent at both five minutes and sixty minutes post-stretch. 

Several studies noted statistically significant decrease in performance immediately following PNF stretching.  Nelson, Cornwell and Heise (1996) found leg strength, jump height, and peak force in countermovement jumps decreased immediately following stretching.  Bradley, Olsen and Portas (2005) studied eight recreational male athletes, and found vertical jump height, peak vertical power, and peak vertical ground reaction force were reduced for twenty minutes post-stretch.  They concluded that thorough stretching can reduce jumping performance, and that this reduction was independent of what type of stretching was utilized.  They concluded with Young and Behm (2003) that a significant stretching regimen could “be detrimental to performance where maximal strength and power is critical” (Bradley, Olsen and Portas 2005, 208).  Shrier (2005) found that both power and force exhibit a slight decrease immediately after stretching in general, and then specifically included PNF stretching in this statement.  The decreases ranged from two- to five- percent, which Shreir did not find to be a significant amount for all but the most competitive athletes.  In the most Weerapong, Hume, and Kolt (2004) recorded reductions in peak torque of the plantar flexors and hamstrings of fifteen to eighteen percent immediately following PNF stretching.

Over the long term, however, regular engagement in PNF stretching was found to strengthen muscle and improve explosive power.  Shrier (2005) determined that stretching done regularly for at least three weeks led to recordable increases in both force and power.  He further concluded that stretching was most beneficial to strength and power gain when performed every day.  Long term gains were found using both PNF stretching and maximum voluntary contraction (MVC) in research by Young, Jenner, and Griffiths (1998).  Stopka et al (2002) conducted considerable research into the effects of PNF stretching and static stretching in mentally handicapped athletes and their coaches.  While primarily focusing on flexibility and muscle length, some consideration was given to strengthening.  They found “PNF stretching improved performance regardless of stretching order” and concluded “individuals of various ages and cognitive abilities can apparently perform and benefit from PNF stretching” (22).  Stone (2000) found that PNF stretching techniques “develop muscular strength in functional patterns of motion” (39). 
Long-term PNF exercises actually produced a significant enough muscle strengthening that it was compared by three researchers to weight training in terms of its effectiveness in strengthening (Stone 2000, Grieco 2002, Shrier 2005). Young and Elliot (2001) similarly found PNF stretching programmes of several weeks or more to increase muscle strength and jumping performance.  In particular, PNF stretching at the end of a workout was found to be more effective in long-term strengthening (Grieco 2002). 

PNF stretching exercises included in this research, prone quadriceps stretch, lying straight leg hamstring stretch, lying calf stretch, and internal rotating gluteal stretch at moderate intensity were similar to the exercise regimen followed by many of the studies just discussed.  While it may be anticipated from the literature reviewed that this training system would produce an increase in strength and explosive power if repeated over a period of weeks or longer, literature suggests it will not be an efficient programme for increasing jump performance in the short term.

Like PNF stretching, dynamic stretching has increased significantly in practice over static stretching, primarily due to its superior results.  Since dynamic stretching results in increased flexibility and range of motion, it has become a favoured part of the warm up programmes of athletes and performers with heavy flexibility needs.  According to Brooks (1998), for example, “professional gymnasts, divers and dancers use dynamic stretching extensively” (269). 

Dynamic stretching, however, involves moving through a motion similar to one used in the sport or athletic event, with a slight stretch throughout the movement. Range of momentum is increased through controlled repetitive motion, with a typical time to complete one repetition of dynamic stretching being in the four to five second range (Brooks 1998).  Exercises involve smooth continuous movement in reciprocal actions, such as lifting the leg and bringing it back down.  These actions begin slowly, but can increase in speed as the stretcher warms up and his or her muscle become looser (Mann and Whedon 2001).  Ideally, dynamic stretches should be effective multidirectionally, and incorporate the whole body, with specific attention given to sport-specific movements (Mann and Whedon 2001).  For example, a tennis player might mimic his or her serve motion, extending the arm just slightly all around each time he or she completes the rotation.  Military walk, toe walk, quadriceps kicks, sumo groin stretch, and any replication of the movement used in the specific sport are other typical dynamic stretching manoeuvres (Mann and Whedon 2001).  It is important that dynamic stretching not exceed a comfortable stretch, and recommended that this type of programme be used prior to workout (Brooks 1998, Mann and Whedon 2001). 

Dynamic stretching has been found to increase blood flow to the target muscle groups while increasing muscle length (Gunner 2004).  This is significant because static stretching has shown muscle elongation but no increased blood flow, and some researchers consider this difference the reason for marked decrease in power and jump performance following static stretching, but little or no decrease in power and jump performance following dynamic stretching (Gunner 2004).  In a study of Canadian hockey players, Gunner (2004) found dynamic stretching provided the surge in blood availability to target muscle groups needed for initial skating.  It is therefore important that dynamic stretching not be continued to the point of fatigue; doing so will negate the increased blood flow result to target muscles and potentially reduce performance (Brooks 1998).  Additionally, dynamic stretching has been recorded to decrease passive muscle stiffness (Weerapong, Hume, and Kolt 2004).

Although dynamic stretching was designed more for muscle conditioning than for simple stretching, few studies of the effect of dynamic stretching on strength and explosive power exist (Walker 2001).  A number do mention or record changes in such as secondary data.  Most research and proponents of the training system use it based on flexibility results, or its potential to lessen the likelihood of injury, and found minor or no effect on power or strength.  Pasquale (2005), in a report of a dynamic stretching sequence used by the Miami Sol, a WNBA basketball team in the United States, reported that the program was implemented to provide effective warm-up, increase flexibility, and prevent injury.  There were no reductions in force or power reported.  Similarly, Larson (2003) describes a dynamic stretching programme designed for volleyball players, which resulted in increased joint range of motion and decrease in injury.  In addition, this report attributes improved muscle efficiency to dynamic stretching.  Siatras et al (2003) conducted an extensive study of the effects of static and dynamic stretching on gymnasts’ vaulting speed.  Contributing factors to increase or decrease in speed included explosive power.  While a decrease in speed and power was recorded following the static stretching protocol, there was no decrease in mean running speed following the dynamic stretching protocol.  Authors attributed this difference to the myotatic reflex producing autogeneic inhibition.  This conclusion is supported by research by Plowman and Smith (1997).  Weerapong, Hume, and Kolt (2004) found dynamic stretching to be “a useful protocol for increasing flexibility without decreasing athletic performance (198).

Some studies have found strength and / or power performance increase following regular dynamic stretching.  Boyle (2000), found that while static stretching led to decrease quadriceps torque both short- and long-term, dynamic stretching resulted in measurable improvements in muscle force performance.  Fletcher and Jones (2004) studied ninety-seven rugby players, some of whom stretched dynamically and some of whom stretched statically.  The group following the active dynamic stretch programme showed a significant decrease in twenty-meter sprint time, with increase in explosive power at start.   The researchers attributed this performance improvement to the rehearsal of specific movements used in the sprint and sprint start, which they believed help increased coordination of subsequent movement during the sprint. 

The dynamic stretch series implemented in this research is therefore anticipated to produce increased muscle elongation and blood flow within the muscle, decreasing the risk of injury.  A series of leg stretches, as they are directly relative to the muscle groups targeted in test jumps, will be implemented in this research.  However, it is anticipated that any impact on strength, force, or explosive power will be slight or statistically insignificant in short-term measurements.

The final training system evaluated in this study, plyometrics, functions in yet a third manner from PNF stretching and dynamic stretching.  Plyometrics were first used by Eastern European track and field athletes in the 1960s (Geiger 2004).  An American coach, watching these athletes’ jump training exercises, named them plyometrics after two Greek terms meaning ‘measurable increases’ (Chu 1999).  Global use in track and field followed almost immediately, based on increased explosive power noted in these Eastern European athletes, and plyometric exercise has since spread to training in almost all athletic sports (Miller et al 2002). 

Plyometrics are used primarily to develop strength and speed in movement.  Typical plyometric exercises include drop jumps, squat hops, box jumps, pendulum swings, and clap push-ups, with drop jumps being the most widely used (Geiger 2004, Walshe and Wilson 1997).  Although commonly used in lower-body workouts, the training system has also been shown to be effective in upper-body strengthening (Seabourne 2000).  In plyometrics, power is generated through what is called the ‘stretch-shortening cycle’ (Miller et al 2002).  The muscle is first rapidly stretched by the body’s weight.  This happens, for example, when crouching down prior to jumping.  Nerve endings then tell the muscle to react equally as fast, shortening in a concentric action by the same muscle (Gieger 2004).  Repeating this process causes the muscle to store elastic energy, which translates into increased explosive power (Geiger 2004).

Numerous studies have documented this increase in explosiveness that results from a regular plyometric regimen.  Lees, Vanretnerghem and De Ciercq (2004) also found increase in maximal and submaximal vertical jump following regular plyometric series.  Miller et al (2002) reported no difference in land-based or aquatic-based plyometric exercise on vertical jump improvement; both were found to provide significant enhancement to performance.  Wilson, Murphy and Giorgi (1996) demonstrated plyometrics increased both acceleration and power, particularly in vertical and depth jumps, a finding reinforced by Holcomb et al (1996).  Hewett et al (1996) studied the effects of plyometric training specifically in highly competitive female athletes, and concluded similar results.  In a study of jumping performance in pre- and post-pubertal boys, Paasuke, Ereline and Gapeyeva (2001) recorded increase in jumping performance and explosive power in both groups.  In an early study of plyometric results, Adams (1984) found the training system let to increased muscular leg strength, increased muscle power, and improved jump performance.  In a more recent study, Hennessy and Kilty (2001) documented the results of adding plyometric warm-ups to the training regimens of highly competitive female athletes.  They found the added exercises contributed to increased sprint speed, leg strength, power and joint awareness.  Bobbert (1990), in an extensive study of drop jumping plyometrics and its effect on jumping ability, concluded that plyometrics improve both vertical jump performance and strength.

Plyometrics can also be used in conjunction with other training methods.  Maffiulette et al (2002) researched the results of combined electrostimulation with plyometric exercises on volleyball players over a two-week period.  They found improvement in vertical jump, in addition to increases in the maximal strength of knee extensors and planar flexors.  Quill (2004) reports that researchers found a free-weight program combined with plyometric exercises resulted in increased strength and power in golf swing compared with either training method employed alone.  Seaborne (2000) describes a plyometric series designed specifically for the upper body, including a number of modified push-ups and work with a medicine ball.  He reports increased upper body strength as the result of this programme. 

Researchers typically reach the consensus, as a result of their studies, that plyometric directly increases explosive power and jump performance.  Chu (1999) reports that with plyometrics, “the athlete’s ability to develop power is enhanced, which leads to improvements in performance (7).  Miller et all (2002) similarly concluded “athletes who efficiently use the stretch-shortening-cycle mechanism through plyometric exercises are batter able to increase acceleration and power” (269).  Geiger (2004) quotes strength and conditioning specialist Neal Pire as stating “plyometric exercises train the body to be more explosive, to move quicker, and to jump higher” (74). 

While plyometrics are often used in injury rehabilitation, care must be taken in this training system since the potential for injury is also high (Moss 2002).  Since these jumps and such are highly intense and create stress on the muscles and joints, lower-body plyometric workouts should be done on a yielding surface that provides some shock absorption (Chu 1999).  It is equally important that the exerciser have some base level of fitness before attempting plyometric exercises (Moss 2002).  One method many are adopting for lower-body improvement with less injury risk is the pendulum swing.  This involves the athlete being suspended in a chair and ‘jumping’ off a wall from a seated position.  Fowler and Lees (1998) found “pendulum exercises resulted in a greater velocity that did drop-jumps” and that this increased velocity let to improved muscle power (273).  As exercises such as the pendulum swing, in addition to a traditional plyometric series, increase risk of injury, trainers and coaches typically recommend work with a professional familiar with plyometric training in beginning and developing a plyometric workout.  They particularly cite the likelihood of injury if exercises are done incorrectly (Geiger 2004).  Even with this potential for injury, however, the improvement in performance from plyometrics are widely felt to be worth the risk.

This research will measure the effect of plyometric training on individuals who are unfamiliar with this type of exercise.  Specifically, a low intensity ankle high hop using both feet, a medium intensity double leg tuck jump, a high intensity single leg tuck jump, and a high intensity double leg zig zag hop will be used; all of these jumps are similar to those described in various studies discussed above, and therefore similar results are expected. 

As research in published literature strongly supports plyometrics as an optimum way to increase power, strength, and jump performance, while results of PNF stretching and dynamic stretching are not as conclusive, it is anticipated that the plyometric series will result in the greatest increase in explosive power output and jump ability in the short-term. 

REFERENCES

Adams, T. (1984).  An investigation of selected plyometric training exercises on muscular leg strength and power.  Track and Field Quarterly Review, vol. 84, no. 4, pp. 36-40.
Alter M. (1988).  Science of Stretching.  Human Kinetics, Champaign, IL, USA.
Bobbert, M. (1990).  Drop jumping as a training method of jumping ability.  Sports Medicine, vol. 9, pp. 7-22.
Boyle, P. (2000).  The effect of static and dynamic stretching on muscle force production.  Conference Communications, pp. 273-274.
Bradley, P., Olsen, P., Portas, M. (2005).  Acute effect of static, ballistic, and proprioceptive neuromuscular facilitation stretching on vertical jump performance.  Journals of Sports Sciences, vol. 23, issue 2, February 2005, p. 208.
Brooks, D. (1998).  Programme Design for Personal Trainers.  Human Kinetics, Leeds.
Carter, A., Kinzey, S., Chitwood, L., Cole, J. (2000).  Proprioceptive Neuromuscular Facilitation Decreases Muscle Activity During the Stretch Reflex in Selected Posterior Thigh Muscles.  Journal of Sports Rehabilitation, vol. 9, pp. 269-278.
Chu, D. (1999).  Plyometrics in Sports Injury Rehabilitation and Training.  Athletic Therapy Today, May 1999, pp. 7-11.
Ellenbecker, T. (2002).  Dynamic Flexibility.  United States Tennis Association (USTA) High Performance Coaching Newsletter, Vol. 4, March 2002.
Fletcher, I., Jones, B. (2004).  The effect of different warm-up stretch protocols on 20-meter sprint performance in trained rugby union players. Journal of Strength and Conditioning Research, vol. 18, issue 4, November 2004 pp. 885-9.
Fowler, N., Lees, A. (1998).  A Comparison of the Kinetic and Kinematic Characteristics of Plyometric Drop-Jump and Pendulum Exercises.  Journal of Applied Biomechanics, vol. 14, pp. 260-275.
Fowles, J., Sale D. (1997).  Time course strength deficit after maximal passive stretch in humans.  Medicine and Science in Sports and Exercise, vol. 29, S26.
Fraser, S. (2004).  Stretch theory:  everyone knows that stretching is good for you.  Or is it?  Current Health, v.31, issue 2, October 2004, pp. 24-5. 
Geiger, D. (2004).  Leaps & bounds:  jump higher, get stronger and increase your explosive energy with plyometrics.  Muscle and Fitness, vol. 5, issues 3, April 2004, pp. 74-80.
Grieco, C. (2002).  PNF Stretching.  American Fitness, July / August 2002, pp. 17-19.
Gunner, R. (2004).  The New Warm-up - Dynamic Stretching.  Canadian Sports Therapy Association [online].  Available at www.canadiansportstherapy.com, accessed 20 April 2005.
Hennessy, L., Kilty J. (2001).  Relationship of the stretch-shortening cycle to sprint performance in trained female athletes.  Journal of Strength Conditioning Research, vol. 15, no. 3, pp. 326-331.
Hewett, T., Stroupe, A., Nance, T., Noyes F. (1996).  Plyometric training in female athletes.  American Journal of Sports Medicine, vol. 24, pp. 765-773.
Holcomb W. (2000).  Improved stretching with proprioceptive neuromuscular facilitation.  Strength Conditioning, vol. 22, pp. 59-61.
Holcomb, W., Lnader, J., Rutland, R., Wilson G. (1996).  A biomechanical analysis of the vertical jump and three modified plyometric depth jumps.  Journal of Strength Conditioning Research, vol. 10, pp. 83-88.
Larson, R. (2003).  Dynamic stretching: USA weightlifting club coach Rett Larson has designed a volleyball stretching program that not only puts excitement into this sometimes mundane task, but also produces maximum results at the same time.  Volleyball, December 2003, pp. 28-32.
Lees, A., Vanrenterghem, J., De Ciercq, D. (2004).  The maximal and submaximal vertical jump:  implications for strength and conditioning.  Journal of Strength and Conditioning Research, vol. 18, issue 4, November 2004, pp. 787-792.
Lewit, K. (1985).  Manipulative Therapy in Rehabilitation of the Motor System.  Butterworth, London.
Maffiuletti, N. et al (2002).  Effect of combined electrostimulation and plyometric training on vertical jump height.  Medicine and Science in Sports and Exercise, vol. 34, issue 10, October 2002, pp. 1638-1644.
Mann D., Jones M. (1999).  Guidelines to the implementation of a dynamic stretching program. Strength Conditioning, vol. 21, no. 6, pp. 53-55.
Mann, D., Whedon, C. (2001).  Functional Stretching:  Implementing a Dynamic Stretching Program.  Athletic Therapy Today, May 2001, pp. 10-13.
McAtee R., Charland J. (1999).   Facilitated Stretching: Assisted and Unassisted PNF Stretching Made Easy.  Human Kinetics, Champaign, Il, USA.
Miller, M., Berry, D., Bullard, S., Gilders, R. (2002).  Comparisons of Land-Based and Aquatic-Based plyometric Programs During and 8-Week Training Program.  Sports Rehabilitation, vol. 22, pp. 268-283.
Moore, M. Hutton, R. (1980).  Electromyographic investigation of muscle stretching techniques.  Medicine and Science in Sports and Exercise, vol. 12, pp. 322-329.
Moss, R. (2002).  Physics, Plyometrics, and Injury Prevention.  Athletic Therapy Today, March 2002, pp. 44-45. 
Nelson, A., Cornwell, A., Heise, G. (1996).  Acute stretching exercises and vertical jump stored elastic energy.  Medicine and Science in Sports and Exercise, vol. 29, S156.
Osternig, L., Robertston, R., Troxel, R., Hansen, P. (1987).  Muscle activation during proprioceptive neuromuscular facilitation (PNF) stretching techniques.  American Journal of Physical Medicine, vol. 66, pp. 298-307.
Pasquale, M. (2005).  Dynamic Stretching Routine for Women's Basketball.  Available at www.bodybuilding.com, accessed 20 April 2005.
Paasuke, M., Eereline, J., Gapeyeva, H. (2001).  Knee extensor muscle strength and vertical jumping performance characteristics in pre and post-pubertal boys.  Pediatric Exercise Science, vol. 13, pp. 60-69.
Plowman, s. and Smith, D. (1997).  Exercise physiology for health, fitness, and performance.  Allyn and Bacon, Boston. 
Quill, S. (2004).  Strong and long.  Men’s Health, vol. 19, issue 6, July-August 2004, p. 204.
Roberts, J., Wilson, K. (1999).  Effect of stretching duration on active and passive range of motion in the lower extremity.  British Journal of Sports Medicine, vol. 33, no. 4, August 1999, pp. 259-63.
Rodacki, A., Fowler, N., Bennet, S. (2001).  The Effect of Postural Variations in Movement Co-Ordination During Plyometric Rebound Exercises.  Journal of Biometrics, vol. 17, pp. 14-27.
Seabourne, T. (2000).  The Power of Plyometrics.  American Fitness, September / October 2000, pp. 64-65.
Shrier, I. (2002).  Does stretching help prevent injuries?  In MacAuley, D., Best, T.,(eds):  Evidence-Based Sports Medicine.  BMJ Publishing, London, pp 97-116.
Shrier, I. (2002).  Does stretching improve performance? a systematic and critical review of the literature.  Clinical Journal of Sports Medicine, vol. 14, no. 5, pp. 267-273.
Shrier, I. (2005).  When and Whom to Stretch?  Physician and Sports-Medicine, vol. 33, issue 3, March 2005. 
Siatras, T. et al (2003).  Static and Dynamic Acute Stretching Effect on Gymnasts’ Speed in Vaulting.  Pediatric Exercise Science, vol. 15, pp. 383-391.
Stone, J. (2000).  Proprioceptive Neuromuscular Facilitation.  Athletic Therapy Today, January 2000, pp. 38-39.
Stopka C., Fouenius C. (1995).  Achieving the Ultra-Stretch.  Burgess, Edina, MN, USA.
Stopka, C. et al (2002).  Stretching Techniques to Improve Flexibility in Special Olympics Athletes and Their Coaches.  Journal of Sports Rehabilitation, vol. 11, pp. 22-34.
Walker, B. (2001).  Warm Up Activities & Stretching Exercises.  The Stretching & Sports Injury Newsletter [online].  Available at www.stretchinghandbook.com, accessed 20 April 2005.
Walshe, A., Wilson, G. (1997).  The Influence of Musculotendinous Stiffness on Drop Jump Performance.  Canadian Journal of Applied Physiology, vol. 22, no. 2, pp. 117-132.
Weerapong, P., Hume, P., Kolt, G. (2004).  Stretching:  Mechanisms and Benefits for Sports Performance and Injury Prevention.  Physical Therapy Review, vol. 9, pp. 189-206.
Wilson G., Murphy, A., Giorgi, A. (1996).  Weight and plyometric training:  effects on eccentric and concentric force production.  Canadian Journal of Applied Physiology, vol. 21, pp. 301-315.
Winters, M. et al (2004).  Passive Versus Active Stretching of Hip Flexor Muscles in Subjects with Limited Him Extension:  A Randomized Clinical Trial.  Physical Therapy, vol. 84, no. 9, September 2004, pp. 800-807.
Young, W., Elliott, S. (2001).  Acute effect of Static Stretching, Proprioceptive Neuromuscular Facilitation Stretching, and Maximum Voluntary Contractions of Explosive Force Production and Jumping Performance.  Research Quarterly for Exercise and Sport, vol. 72, issue 3, September 2001, p. 273-282.
Young, W., Jenner, A., Griffiths, K. (1998).  Acute enhancement of power performance from heavy load squats.  Journal of Strength and Conditioning Research, vol. 12, pp. 82-84.

All of the essays in this section were written by students and then submitted to us to publish and help others. Thanks to all of the students who have submitted their essays to us. You should not hand in our essays as your own. We do not condone plagiarism! If you need custom essays on your exact essay questions, then have a look at our essay writing service.

Sign up and be the first to receive our latest offers: