Warm-Up and Stretching Procedures

A majority of patients involved in rehabilita­tion—athletes and non-athletes alike—perform some type of preliminary physical activity or warm-up procedure, especially if a strenuous workout is expected. Warming up provides numerous benefits. An accelerated metabolic rate promotes the effi- cient use of substrates needed to pro- ; vide energy for physical activity. A i rise in muscle temperature reduces the : internal viscosity of muscle proto- I plasm, enhancing the mechanical effi- i ciency of moving muscles. Recent ! research indicates that mild warm-up exercise could inhibit the development of intrucellulur acidosis during subse­quent intense exercise.1 Muscle con­traction is more rapid and forceful when muscle temperature is slightly ; higher than body temperature. An ele­vated body temperature stimulates : vasodilation, increasing blood flow j through the vascular bed of muscle tis- j sue and increasing substrate delivery. : An adequate warm-up appears to minimize the risk of injury to the mus­cles, tendons, ligaments, and other j connective tissues, possibly because of \ improved elasticity from blood satura­tion.2 Therefore, the most common I static stretch procedures before warm- ]-ing up must be reconsidered. A warm-up may also reduce the incidence of | subendocardial ischemia and improve ; blood pressure response to exercise. It is clear that a warm-up should precede | participation in any type of vigorous [ rehab activity. Types of Warm-Up Any effective type of warm-up should produce increased muscle temper­ature. Passive warm-up raises the body tempera-lure by some external means (a hot shower, for example). A general or nonspecific warm-up involves active motion of major muscle groups, as in simple calisthenics. Specific warm-up focuses on the neu-romuscular regions to be used in the anticipated exercise (a rehearsal of the exercise event taking place), making this method the most effective for rehab patients. The intensity and dura­tion of warm-up should be individual­ized according to the patient's physical capabilities. A rectal temperature rise of 1° to 2° C seems adequate, and is usually accompanied by the onset of sweating in normal environmental conditions. Too intense a warm-up should not be done too far in advance of exercise, as the body temperature returns to normal after about 45 min­utes of rest. Some believe that the benefits of warming up may be related, in part, to psychological factors. Warm-up before exercise is a gener­ally accepted practice.1 Genovely, et til4, examined the effects of prolonged warm-up exercise at 40% and 68% of maximal aerobic capacity (below and above anaerobic threshold, respective­ly) on maximal performance in five men who were active regularly, but were not highly trained. Maximal per­formance, consisting of two 40-second bouts of maximal pedaling against a 5.5-kg resistance, was tested without warm-up exercise. The two bouts of maximal exercise, separated by a five-minute rest period, were found to be reproducible for work output and peak blood lactate level. Below anaerobic threshold, warm-up exercise significantly increased core temperature with no rise in the steady-state blood lactate level. It did not contribute to improved maximal performance. Above anaerobic threshold, warm-up exercise led to significant increases in both core temperature and steady-state blood lactate level; work output and peak blood lactate concentration on maximal exercise were significantly reduced. Task-specific, prolonged warm-up exercise below anaerobic threshold does not contribute to improved maxi­mal performance, while warm-up exer­cise above the anaerobic threshold impairs maximal performance. This probably is due to glycogen depletion in fat-twitch muscle fibers, which, in turn, may have contributed to decreased lactate production. These findings apply to short-term maximal exercise in a setting in which the psy­chological aspects of testing are rigidly controlled. In recent years, more flexibility exercises are included in most warm-ups. The warm-up should be exercise specific, and the type of drills used should prepare the patient for the skills they will use. The warming-up should not be exhausting and should prepare the patient, both physically and men­tally, for their rehabilitative events. Static Stretching Exercise The 1999 study by Johansson, et til, suggests that pre-exercise static-stretching "has no preventive effect on the muscular soreness, tenderness and force loss that follows heavy eccentric exercise."5 Shrier'1 and Pope, et al,1 conclude that stretching before exer­cise does not reduce the risk of exer­cise-related injury. Dominguez8 believes that stretching, particularly static stretching, is, itself, a significant cause of injuries. The hurdler's stretch and the plow, in which the patient is supine with the legs raised up and over the head so the feet touch the ground behind the shoulders, are specific examples of static stretching exercises deemed to be harmful. He does favor a 15-minute warm-up of gentle range-of-motion exercises (ROM) for indi­viduals who perform explosive activi­ties, but advises most to merely start slowly and finish with a gentle cool-down, bending and rotating the hips, knees, ankles, and shoulders. The ben­efits associated with stretching are attributed to active, controlled exercis­es, not static stretching, itself. Dominguez9 also believes that, rather than seeking flexibility, most should attempt to develop dynamic ranges of motion. The ability to actively control joints through the full range of motion can be promoted by a combination of gentle flexing, extend­ing, sideways bending, and rotation. A good overall program should develop range of motion, strength, power, endurance, balance, and motor control. Nothing more than oversized rubber bands (rehab tubing), balls, teeter-boards, and balance beams is needed. Dominguez feels there is much room for creativity as clinicians apply gener­al techniques to individual needs. Flexibility Exercise In the past few years, static flexibili­ty exercises have gained a great deal of popularity. However, many clinicians have gone beyond this, and are using proprioceptive neuromuscular facilita­tion (PNF) techniques to increase flex­ibility. Warnings began to appear in the literature that some of the exercises might actually be harmful. •"Bouncing could tear a muscle." "Stretch the muscle and not the tendon." "Hur­dler's stretch can damage the medial aspect of the knee." "The plow is bad for the cervical spine." "The ballet stretch is dangerous." However, most believe that flexibility done in modera­tion, when the muscles are warmed up, can be beneficial. There are, obvious­ly, some exercises that should be avoided. Attempts should be made in general to stretch muscle bellies and not tendons. This can be done by slightly relaxing the joints which the stretched muscles pass over. Never stretch a cold muscle. Most of the flexibility program should be done at the end of a rehab program. Surberg1" points out that there is an optimal level of flexibility that allows efficient movement, while reducing the risk of certain types of injury. Attainment of this level of flexibility, usually, is a goal of rehab conditioning programs. The first step, after certain injuries, is achievement of normal ROM. Flexibility or ROM can be increased by reducing the resistance of agonist muscle groups, or by increas­ing the strength of opposing muscles. Decreasing the resistance of an agonist muscle group can be accomplished by lengthening connective tissues or by relaxing the myotatic reflex. Certain PNF methods may increase the strength of opposing muscles, whereas others influence agonist muscle groups. Flexibility or ROM exercises include passive or active, and com­bined active and passive, movements. Passive movements involve guiding a body part through a ROM. with or without a prolonged stretch at the end of the movement. Active ROM involves the slow movement of an extremity of body part, until resistance precludes further movement. Several variations in these methods exist. Kim D. Christensen, DC, CCSP, DACRB, is co-director of the SportsMedicine & Rehab Clinics of Washington. He is a popular speaker and participates as a team physician and consultant to high school and uni­versity athletic programs. He is cur­rently a postgraduate faculty member of numerous chiropractic colleges and is the president of the American Chiro­practic Association (ACA) Rehab Council. Dr. Christensen is the author of numerous publications and texts on musculoskeletal rehabilitation and nutrition. He can be reached at Chi- ii'jir,:,tic Rehabilitation Assoc, 18604 NW64thAve.. Ridge field. WA 98642.0 References Kato Y. Ikata T el al. Effects of specific warm-up at various intensities on energy metabolism during subsequent exercise. J Sports Med Ph\s Fitness 2000: 40(2): 126- 130. Shellock FG. Physician Sponsmed 1983: ll(Oct):134-139. 3. American College of Sports Medicine posi- tion stand. The recommended quantity and quality of exercise for developing and main­taining cardiorespiratory and muscular fit­ness, and flexibility in healthy adults. Med Sci Sports Exert 1998: 30(6):975-991. 4. Genovely H. Stamford BA. Effects of pro- longed warm-up exercise above and below anaerobic threshold on maximal perfor­mance. Eur J Applied Physiol 1982; 48(Apr):323-33O. 5. Johansson PH. Lindstrom L et al. The effects of preexercise stretching on muscular sore­ness, tenderness and force loss following heavy eccentric exercise. Scand J Med Sci Sports 1999: 9(4):219-225. 6. Shrier I. Stretching before exercise does not reduce the risk of local muscle injury: a criti­cal review of the clinical and basic science literature. Clin J Sport Med 1999: 9<4):221-227. 7. Pope RP. Herbert RD. et al. A randomized trial of preexercise stretching for prevention of lower-limb injury. Med Sci Sports Exerc 2OO0:32(2):271-277. 8. Shyne K. Physician Sponsmed 1982; I ()(Sept): 137-140. 9. CRA. Chiropractic Rehabilitation Standards Manual. Chiropractic Rehabilitation Associ­ ation. 1989. 10. Surberg PR. Athletic Training 1983: 18(Spr):37-4O. O