Stretching has long been a part of athlete training, defined as “… the application of force to musculotendinous structures in order to achieve a change in their length, usually for the purposes of improving joint range of motion (ROM), reducing stiffness or soreness, or preparing for (physical) activity” (3, p. 3). Flexibility is the ROM of a joint or a related series of joints, such as the spine (61,84). Stretching for increased flexibility tends to be uncomfortable, seeking to enhance stretch tolerance by relatively extreme body positions that put muscles and tendons under unaccustomed tensile stresses (51,53). Stretching as a preparatory activity (i.e., warm-up) is clearly not intended to help an athlete “recover” because the stretching precedes the bulk of the training lesson. Stretching to reduce stiffness and soreness is a therapeutic aspect of stretching that is distinct from the other concepts listed above (87). Thus, the term “stretching” can be somewhat paradoxical by application to several diverse purposes. For example, Kisner and Colby (44, p. 187) differentiate between stretching and “ROM exercises,” with stretching involving tissue tensions and lengths beyond those normally available, whereas ROM exercises seek to keep movements within the current boundaries of tissue extensibility (2, p. 5).
There are a number of confusing notions about stretching, flexibility, and recovery. For example, the ROM of a joint almost always is determined statically or passively, whereas the actual expression of ROM in sport is usually dynamic (87, p. 311). As a desirable property of movement, and the link between stretching and flexibility, Siff (81, p. 123), has commented that movement proficiency is based on a balance of static and dynamic positions and motions and that tissues must be conditioned to withstand deformations and shocks. In terms of recovery, stretching seeks to achieve motion that is pain free, unencumbered, and coordinated. However, other activities and modalities can enhance ROM in the short term. Heat, cold, vibration, massage, hydrotherapy, anesthetics, and other modalities have been shown to reduce pain and enhance ROM (41,47,61,73–75).
Stretching can be categorized as active or passive, static or dynamic, and acute or chronic (61). Active stretching refers to a limb position that places a joint at its extreme ROM by virtue of the tension obtained from agonist muscles (e.g., while standing, raising a straight leg from the hip in flexion using the tension from hip flexors). Active stretching positions are opposed by the antagonist muscles' elastic and viscous resistances (e.g., while standing, raising a straight leg from the hip in flexion is resisted by hip extensor muscles and resistive properties of tendons, ligaments, skin, and fascia). Passive stretching involves placing a joint in an extreme ROM position by the use of gravity or inertia (e.g., a gymnast or dancer sitting in a split position or swinging a limb to an extreme position). Static stretching is the most commonly prescribed type of stretching involving placement of the body and limbs in an extreme ROM position and holding this position for a period by gravity, partner assistance, or agonist muscle tension. Dynamic stretching moves joints through extreme ROM movements without long pauses or holds and momentarily taking a limb to an extreme position (e.g., swinging the leg at the hip, forward and backward in the sagittal plane, momentarily stretching hip flexors and extensors). Acute stretching refers to a single exercise or stretching for a relatively short duration, usually 30 seconds or less (6,68). Chronic stretching refers to repeated stretching exercises or sets of exercises over days and weeks.
Stretching to develop semipermanent ROM improvements relies largely on the achievement of “stretch tolerance” (50,52,54). Achievement of stretch tolerance requires focused practice in extreme and uncomfortable ROM positions. Stretching discomfort is difficult to quantify but relates directly to stretching intensity and pain tolerance (11, p. 2, 18,30). The presence of discomfort or pain in an effort to achieve recovery appears contradictory to the concept of recovery. However, the discomfort level of stretching often has been prescribed as tension remaining below a pain threshold (2, pp. 58, 145), without considering that an optimal discomfort and tension level may be obtained in a different position that results in the more effective achievement of a new ROM. Moreover, the inducement of pain also appears to contradict the concept of recovery-relaxation (2, p. 5, 62,71).
Recovery is usually defined as the process of returning something that was lost (85, pp. 260–261). “Mostly, recovery is defined as the compensation of deficit states of an organism (e.g., fatigue or decrease in performance) and, according to the homeostatic principle, a reestablishment of the initial state” (39, p. 6). However, recovery in sport is a 2-stage process: returning what was lost (i.e., reducing fatigue) and adapting or supercompensating to training demands (85, pp. 260–261). Adaptation results from the interplay of work and recovery. Recovery is not, and should not be, considered complete or effective unless the athlete reaches a higher state of fitness after recovery (61,85, pp. 260–261). Thus, simply reducing fatigue or returning to a nonfatigued state represents incomplete recovery. Moreover, the ultimate test of recovery-adaptation lies in the transfer of newly acquired fitness and/or skill to actual sport performance (10, pp. 1–21, 14,87, pp. 173–174).
ARE STRETCHING AND RECOVERY COMPATIBLE?
In terms of recovery, the primary objective of stretching should be to achieve enhanced ROM and/or reduced stiffness and soreness. The acute effects of stretching are short-lived, from seconds to minutes (21,22,28,43,45,82,93). Supporting Wolff's law (function determines structure), semipermanent changes in ROM require focused training for days to months (13,23,46,65). Acute therapeutic stretching may return ROM after immobilization from injury (55,58,72) and quasi-therapeutically in dynamic “loosening” activities to promote ease of motion after warm-up and/or cooldown activities (1,15,38,89), as a means of developing concentration control (27,42) and the ability to cope with chronic pain (78,79,91). The difference in stretching and ROM exercise concepts, as described above, has been noted by Verkhoshansky and Siff (87, pp. 173–174), who have attributed some gains in ROM to changes in muscle and tendon stiffness and neuromuscular properties. If stretching is included in recovery efforts, the movements should be dynamic and pain free, contraindicating stretching positions that elicit discomfort and pain.
The role of stretching and recovery has a relatively long, and somewhat confusing, history. As early as 1961, de Vries (19) observed reduced muscle distress after static stretching. Static stretching has been shown to reduce electromyographic median frequency fatigue of back extensor muscles and thereby enhanced coping with chronic pain (24). Smaller decreases and more rapid return of strength after delayed onset muscle soreness (DOMS) were observed using static and proprioceptive neuromuscular facilitation stretching (16). Stretching via pain-free motions with minimal resistance may enhance postexercise strength, ROM, and recovery (62). Heat-shock protein incursion of immobilized rat gastrocnemius muscle was reduced after static stretching and was thought to protect the muscle against reloading injury after immobilization (34). Cold combined with stretching was superior to either alone or heat in reducing postexertional pain (67).
In contrast to the previous paragraph, an acute reduction in muscular strength after fatiguing exercise has been shown to continue after static stretching for recovery (25). Maximal voluntary contraction force remained unchanged, whereas reflex and stretch-shortening parameters were reduced after fast, repeated muscle stretching (5). Pre-exercise stretching was not effective in reducing postexercise soreness and reduced force abilities (36). In a study of active exercise, passive resting, and stretching for recovery from isokinetic knee extensions at 50% maximal voluntary contractions to fatigue, active recovery (i.e., light exercise, cycling with no resistance) showed better return to baseline recovery (62). Active recovery was better in returning strength-endurance performance than either passive recovery or stretching, which did not differ from each other (62). Cold-water immersion was better than carbohydrate supplementation and stretching on recovery of basketball players participating in a 3-day tournament (62). Heat, cold, and stretching groups performing stair running did not achieve enhanced recovery over a control group (69). Rat sciatic nerve axonal retrograde transport (i.e., intracellular material movement toward the cell body from the terminal ending) was inhibited by 6% strain (10% neuron lengthening) stretching. This rodent study showed that stretching caused ischemia and increased neuron tensile forces (86).
The reduction of pain via stretching is a laudable goal for recovery activities. However, perceived muscle pain was not relieved by static stretching (59). Stretching pre- and posteccentric exercise did not reduce DOMS (90). Inconsistent results were obtained using warm-up, stretching, and massage treatments to reduce soreness after eccentric exercise (70). Recovering from traumatic muscular injury usually seeks to ensure rapid return of ROM within the constraints of tissue healing. However, more recent work has shown that return to activity should be based on full recovery of the muscle and tendon unit and that programs based solely on stretching and strengthening result in poorer outcomes (35). A review of DOMS and effective treatments concluded that cold therapy, stretching, homeopathic remedies, ultrasound, and electrical modalities had little or no influence on the alleviation of muscle soreness or other DOMS symptoms (17).
CAN STRETCHING FOR RECOVERY BE QUANTIFIED?
A serious problem permeates nearly all studies of stretching—how does one measure stretching intensity? How does one determine if the stretching activity elicited slightly uncomfortable, moderately uncomfortable or painful sensations during stretching? Individual athletes have idiosyncratic tolerances for pain. Moreover, discomfort and pain may be exercise specific (61). Soreness and stiffness may elicit pain and reduced ROM that inhibits the use of even small ROM movements thereby presenting a new stress rather than the reduction of stress. There does not appear to be a single metric ever proposed to ascertain the level, intensity, or magnitude of stretching, short of static measurements of maximum ROM positions (e.g., sit-and-reach tests) that are too often completely lacking in a conceptual framework and sport specificity (33). As such, how can any judgment of the effectiveness of stretching on recovery be determined? The subject or athlete is usually directed to perform movements that are pain free, but the line between mere discomfort and pain is not clear (11, p. 2,18,30). Moreover, the tolerance of discomfort and pain is likely to be greater during short duration exposures as opposed to those of longer duration (4,63,76). Some athletes may perform extreme positions more zealously and achieve greater ROM or incur and endure greater discomfort than studymates (63). Stretching studies are inherently incomparable if there is no standard means of measuring the stretching effort.
CAN STRETCHING PREVENT RECOVERY AND ADAPTATION?
There is a consensus that serious stretching (i.e., flexibility-related stretching that is uncomfortable and intended to enhance ROM rather than relaxation through acquisition of stretch tolerance, 54) results in reduced strength and power after stretching exercises. The deleterious effects may not be reversed by transitional exercises, and the effect can last up to an hour (8,9,12,37,56,60,88). Unskilled, reckless, and unsupervised use of ballistic stretching (e.g., powerful jerking-type stretch) actually causes muscle soreness and stiffness and is therefore contrary to the idea of enhancement and maintenance of relaxation and pain-free, fluid motion (87).
Recovery modalities, such as heat, cold, hot/cold contrast, hydrotherapy, massage, light exercise, electrical stimulation, and nutritional supplementation, rely heavily on increasing overall blood flow to sore areas of the body. Paradoxically, in a conceptual model of recovery, it was postulated that cooldown activities and stretching accelerate the elimination of waste products, despite evidence that stretching decreases blood flow. Blood flow, capillary region oxygenation, and velocity of red blood cells decrease during stretching (57,66,83). However, one study of ballet-trained athletes and untrained controls indicated that oxygenation during pain-free stretching of the anterior tibialis muscle was better maintained in the ballet-trained athletes (64). Although the fascicle lengths of the anterior tibialis muscles were measured in both groups, one wonders about the choice of muscle in this study because of the difficulty of stretching this muscle. In this study, one could argue that the anterior tibialis was simply lengthened with little or no accompanying discomfort.
Reduction of edema, both local and systemic, are important objectives of the recovery process but are poorly understood by practitioners. Moreover, the new “frontier” in recovery probably lies in the study and control of training-induced inflammation and associated edema (20,26,29,32,48,49,77). Reduction of edema is reliant on free lymphatic fluid flow, and the accumulation of cellular debris from exercise can obstruct lymphatic uptake of fluids (77). Herbert and Gabriel performed a meta-analysis of the effects of stretching on muscle soreness and the risk of injury and found that “Stretching before or after exercising does not confer protection from muscle soreness” (32, p. 468). However, there may be a connection between movements such as combinations of stretching and contraction that may mechanically aid lymphatic flow and venous return and thereby help control sports-related edema and posttraining soreness (92).
CONCLUSIONS AND PRACTICAL APPLICATIONS
The emphasis on dynamic movements rather than static stretch positions is important for recovery stretching. In a review of recovery modalities, Barnett wrote the following for athlete recovery between events: “… there is no compelling scientific evidence to support the use of contrast temperature water immersion therapy, hyperbaric oxygen therapy, nonsteroidal anti-inflammatory drugs, compression garments, stretching, electromyostimulation, and combination modalities” (emphasis added) (7, p. 781). As we learn more about recovery, investigations may focus more light on many modalities and some effectiveness may yet be apparent. However, one would be wise to question the relevance and effectiveness of stretching in sport, particularly stretching for recovery.
Possibly the most heretical remark to make about stretching is to suggest that the dedicated use of stretching sessions may not even be necessary, especially since many athletes dispense entirely with special stretching or even warm-up sessions before or after training without suffering injury in training or competition. The prescription of stretching and warm-up or cooling down sessions has become a well-accepted ritual, but that does not imply that this is essential (87, p. 192).
Stretching exercises should be varied under the same principle as strengthening exercises, but rarely are (35,80). Light training followed by pain-free stretching is proposed as an effective means of achieving an active recovery that was superior to taking a day off from training (40). Finally, a meta-analysis update of 12 studies, one including over 2,000 subjects, showed that pre- and post-activity stretching reduced muscle soreness from 1 to 3 days after exercise by one point in a 100-point scale. The authors concluded that although the results were statistically significant, the magnitude of effect was not clinically significant (31). Practitioners are encouraged to consider recovery stretching carefully, that the activity is not a panacea, and prescription of recovery stretching should not be undertaken blindly, unskillfully, and without careful monitoring.
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