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Kimberly Pratt and Richard Bohannon

Context:

Stretching exercise regimens are routinely prescribed to increase range of motion (ROM) and diminish injuries.

Objective:

To examine the effect of a 3-minute passive stretch on ankle-dorsiflexion ROM in a nonpathological population.

Setting:

University laboratory.

Design:

Prospective, randomized, controlled study.

Participants:

24 apparently healthy volunteers.

Interventions:

Subjects stood with their heels suspended from the edge of a platform. The experimental subjects stretched for 3 minutes on 3 consecutive days.

Main Outcome Measures:

Passive ankle-dorsiflexion ROM.

Results:

Ankle-dorsiflexion ROM increased significantly (P < .0005) over the course of each day’s stretch. No significant gains in ankle-dorsiflexion ROM were realized over 3 days.

Conclusions:

These findings suggest the need for further research to determine the stretching frequency and duration that will result in lasting increases in ankle-dorsiflexion ROM

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Sandro R. Freitas, João R. Vaz, Paula M. Bruno, Maria João Valamatos, Ricardo J. Andrade and Pedro Mil-Homens

Static stretching with rest between repetitions is often performed to acutely increase joint flexibility.

Purpose:

To test the effects of the lack of resting between stretching repetitions and the minimal number of stretching repetitions required to change the maximal range of motion (ROM), maximal tolerated joint passive torque (MPT), and submaximal passive torque at a given angle (PT).

Methods:

Five static stretching repetitions with a 30-s rest-interval (RI) and a no-rest-interval (NRI) stretching protocol were compared. Participants (N = 47) were encouraged to perform the maximal ROM without pain in all the repetitions. Each repetition lasted 90 s. Maximal ROM, MPT, PT, and muscle activity were compared between protocols for the same number of stretching repetitions.

Results:

The NRI produced a higher increase in maximal ROM and MPT during and after stretching (P < .05). PT decreased in both protocols, although the NRI tended to have a lower decrement across different submaximal angles (.05 < P < .08) in the initial range of the torque-angle curve. Significant changes in maximal ROM (P < .01) and PT (P < .01) were obtained at the 3rd and 2nd repetitions of RI, respectively. The RI did not significantly increase the MPT (P = .12) after stretching; only the NRI did (P < .01).

Conclusions:

Lack of rest between repetitions more efficiently increased the maximal ROM and capacity to tolerate PT during and after stretching. The use of 30 s rest between repetitions potentiates the decrease in PT. Rest intervals should not be used if the aim is to acutely increase maximal ROM and peak passive torque.

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Andrew R. Mohr, Blaine C. Long and Carla L. Goad

Context:

Many athletes report that foam rollers help release tension in their muscles, thus resulting in greater range of motion (ROM) when used before stretching. To date, no investigators have examined foam rollers and static stretching.

Objective:

To determine if foam rolling before static stretching produces a significant change in passive hip-flexion ROM.

Design:

Controlled laboratory study.

Setting:

Research laboratory.

Participants:

40 subjects with less than 90° of passive hip-flexion ROM and no lower-extremity injury in the 6 mo before data collection.

Interventions:

During each of 6 sessions, subjects' passive hip-flexion ROM was measured before and immediately after static stretching, foam rolling and static stretching, foam rolling, or nothing (control). To minimize accessory movement of the hip and contralateral leg, subjects lay supine with a strap placed across their hip and another strap located over the uninvolved leg just superior to the patella. A bubble inclinometer was then aligned on the thigh of the involved leg, with which subjects then performed hip flexion.

Main Outcome Measure:

Change in passive hip-flexion ROM from the preintervention measure on day 1 to the postintervention measure on day 6.

Results:

There was a significant change in passive hip-flexion ROM regardless of treatment (F 3,17 = 8.06, P = .001). Subjects receiving foam roll and static stretch had a greater change in passive hip-flexion ROM compared with the static-stretch (P = .04), foam-rolling (P = .006), and control (P = .001) groups.

Conclusions:

Our results support the use of a foam roller in combination with a static-stretching protocol. If time allows and maximal gains in hip-flexion ROM are desired, foam rolling the hamstrings muscle group before static stretching would be appropriate in noninjured subjects who have less than 90° of hamstring ROM.

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Caroline Nicol and Paavo V. Komi

Magnitude of the reflex contribution to force enhancement was investigated in vivo during passive stretches of the Achilles tendon (AT) of one female subject. Thirty passive (5 × 6) dorsiflexions were induced by a motorized ankle ergometer. Achilles tendon force (ATF) was sensed by a buckle transducer applied surgically around the right AT. Single passive stretches resulted in a low but rather linear ATF increase in the absence of EMG (surface electrodes) activity. In the presence of reflexes, a clear ATF enhancement occurred 13–15 ms after the beginning of the EMG reflex responses. In double dorsiflexions at either 1.2 or 1.9 rad · s-1, which were separated by a maintained stretched position of either 40 or 90 ms, the first stretch resulted in initial linear ATF increase, followed by an additional force enhancement during the plateau phase. This reflexly induced increase represented 94 ± 4 N and 184 ± 1 N, respectively, for the 40 and the 90 ms plateaus, corresponding to 210 ± 85% and 486 ± 177% enhancements as compared to the first passive stretch effect. The results suggest further that timing of the stretch during the twitch response influences the magnitude and rate of force potentiation.

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Bradley T. Hayes, Rod A. Harter, Jeffrey J. Widrick, Daniel P. Williams, Mark A. Hoffman and Charlie A. Hicks-Little

Context:

Static stretching is commonly used during the treatment and rehabilitation of orthopedic injuries to increase joint range of motion (ROM) and muscle flexibility. Understanding the physiological adaptations that occur in the neuromuscular system as a result of long-term stretching may provide insight into the mechanisms responsible for changes in flexibility.

Objective:

To examine possible neurological origins and adaptations in the Ia-reflex pathway that allow for increases in flexibility in ankle ROM, by evaluating the reduction in the synaptic transmission of Ia afferents to the motoneuron pool.

Design:

Repeated-measures, case-controlled study.

Setting:

Sports medicine research laboratory.

Participants:

40 healthy volunteers with no history of cognitive impairment, neurological impairment, or lower extremity surgery or injury within the previous 12 mo.

Intervention:

Presynaptic and postsynaptic mechanisms were evaluated with a chronic stretching protocol. Twenty subjects stretched 5 times a wk for 6 wk. All subjects were measured at baseline, 3 wk, and 6 wk.

Main Outcome Measures:

Ankle-dorsiflexion ROM, Hmax:Mmax, presynaptic inhibition, and disynaptic reciprocal inhibition.

Results:

Only ROM had a significant interaction between group and time, whereas the other dependent variables did not show significant differences. The experimental group had significantly improved ROM from baseline to 3 wk (mean 6.2 ± 0.9, P < .001), 3 wk to 6 wk (mean 5.0 ± 0.8, P < .001), and baseline to 6 wk (mean 11.2 ±0.9, P < .001).

Conclusions:

Ankle dorsiflexion increased by 42.25% after 6 wk of static stretching, but no significant neurological changes resulted at any point of the study, contrasting current literature. Significant neuromuscular origins of adaptation do not exist in the Ia-reflex-pathway components after a long-term stretching program as currently understood. Thus, any increases in flexibility are the result of other factors, potentially mechanical changes or stretch tolerance.

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Gregory S. Ford, Margaret A. Mazzone and Keith Taylor

Design:

Pretest–posttest.

Objective:

To determine the effect of 4 durations of static hamstring stretching on knee-extension passive range of motion (KE-PROM).

Context:

Effects of longer (90 and 120 seconds) static hamstring stretching on PROM have not been established relative to more typically recommended 30- or 60-second durations.

Subjects:

35 healthy college-age subjects with >20° loss of KE-PROM.

Outcome Measure:

KE-PROM.

Intervention:

5-week program of single daily stretch for 30, 60, 90, or 120 seconds.

Results:

Static stretching was effective in increasing KE-PROM regardless of stretch duration (P < .0001). A significant improvement was identified in mean PROM for each stretching group, but no difference existed among the 4 stretch-duration groups. The control group’s mean PROM decreased (mean = -3.2°, SD = 1.9), whereas each stretching group increased PROM (means 1.9° to 3.6°).

Conclusions:

Five weeks of daily static hamstring stretching for 30, 60, 90, or 120 seconds increase KE-PROM. Similar benefits were achieved regardless of stretch duration, suggesting that clinicians need not perform static hamstring stretches of more than 30 seconds.

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Reed Ferber, Denise C. Gravelle and Louis R. Osternig

The effects of proprioceptive neuromuscular facilitation (PNF) on joint range of motion (ROM) for older adults are unknown, and few studies have investigated changes in joint ROM associated with age. This study examined PNF stretch techniques' effects on knee-joint ROM in trained (T) and untrained (UT) older adults. Knee-joint ROM was tested in T and UT adults age 45–55 and 65–75 years using 3 PNF stretch techniques: static stretch (SS), contract-relax (CR). and agonist contract-relax (ACR). The 45–55 UT group achieved significantly more ROM than did the 65–75 UT group, suggesting an age-related decline in ROM. The 65–75 T group achieved significantly greater knee-extension ROM than did their UT counterparts, indicating a training-related response to PNF stretch techniques and that lifetime training might counteract age-related declines in joint ROM. The ACR-PNF stretch condition produced 4–6° more ROM than did CR and SS for all groups except the 65–75 UT group, possibly as a result of lack of neuromuscular control or muscle strength.

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Christos Papadopoulos, Vasilios I. Kalapotharakos, Georgios Noussios, Konstantinos Meliggas and Evangelia Gantiraga

Objective:

To examine the effect of static stretching on maximal voluntary contraction (MVC) and isometric force-time curve characteristics of leg extensor muscles and EMG activity of rectus femoris (RF), biceps femoris (BF), and gastrocnemius (GA).

Design:

A within subjects experimental design.

Participants:

Ten healthy students were tested after a jogging and a jogging/stretch protocol.

Intervention:

The stretching protocol involved a 10 min jog and seven static stretching exercises.

Main Outcomes:

Measurements included MVC, time achieved to MVC (TMVC), force at 100ms (F100), index of relative force (IRF), index of rate of force development (IRFD), and average integrated EMG activity (AEMG).

Results:

There were slight but no significant changes in MVC (1%), TMVC (4.8%), F100 (7.8%), IRF (1%), and IRFD (3.5%) between measurement. A significant difference (21%; P < 0.05) in AEMG of RF was found.

Conclusions:

The present study indicated that a moderate volume of static stretching did not alter significantly the MVC and the isometric force-time curve characteristics. Neural inhibition, as it is reflected from AEMG of RF, did not alter MVC and isometric force-time curve characteristics.

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Ulrike H. Mitchell, J. William Myrer, J. Ty Hopkins, Iain Hunter, J. Brent Feland and Sterling C. Hilton

Background and Purpose:

Proprioceptive neuromuscular facilitation (PNF) stretches are widely used in athletics and rehabilitation. Although it has been shown that they produce better range-of-motion (ROM) increases than the slow or static stretch, the mechanisms responsible remain an enigma. This study was conducted to determine whether the previously proposed neurophysiological mechanisms of reciprocal inhibition and autogenic inhibition are responsible for the success of PNF stretches. In addition, the authors assessed the existence of the phenomenon of successive induction because it is used to strengthen reciprocal inhibition.

Methods:

Eighteen subjects 17–44 y performed the PNF stretches contract-relax (CR) and contract-relax, agonist contract (CRAC). EMG data were collected from the medial hamstring muscles via surface and indwelling wire electrodes and analyzed for reciprocal inhibition and successive induction, as well as autogenic inhibition (surface electrodes only).

Results:

Reciprocal inhibition was not evident. The results indicated an elevated rather than an inhibited EMG during the antagonist contraction, possibly representing cocontraction. The authors did confirm the presence of successive induction. Autogenic inhibition was also not evident, and the expected inhibition and therefore lower EMG values after muscle contraction were not observed; instead, they were higher than baseline.

Conclusion:

Previous neurophysiological explanations for mechanisms of PNF stretching appear to be inadequate. This study corroborates previous findings that a muscle’s tone increases during its antagonist’s contraction. Other explanations should be considered regarding the mechanism for the effectiveness of the CRAC and CR PNF techniques in a nonneurologically impaired population.

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Che-Hsiu Chen, Tsun-Shun Huang, Huei-Ming Chai, Mei-Hwa Jan and Jiu-Jenq Lin

Context:

Recent studies have shown that the static stretch (SS) may adversely affect leg-muscle performance.

Objectives:

The authors examined the short-term effects of 2 stretching exercises on hamstrings muscle before and after exercise.

Design:

Crossover.

Setting:

Laboratory.

Participants:

9 healthy, physically active men.

Interventions:

There were 3 protocols in a randomized order with a 7-d interval: nonstretching (CON protocol), hamstrings static stretching (SS) with proprioceptive neuromuscular facilitation (PNF), and SS with kinesio-taping application on the hamstrings.

Main Outcome Measures:

Outcome measures included first-felt and maximum tolerant-felt range of motion (FROM and TROM), maximal knee-flexion peak torque (PT) at 180°/s, and hamstrings muscle stiffness.

Results:

Groups were not different at prestretching in terms of hamstrings flexibility, PT, and muscle stiffness. At poststretching, both stretching protocols showed significant increases in FROM and TROM (P < .05). Stiffer hamstrings muscle and decreased PT were found in both SS+PNF and CON protocols (P < .05). However, there was no significant difference in the SS+Taping protocol (P > .05).

Conclusion:

The stretching protocols improve hamstrings flexibility immediately, but after exercise hamstrings peak torque is diminished in the SS+PNF but not in the SS+Taping group. This means that SS+Taping can prevent negative results from exercise, which may prevent muscle injury.