Wednesday, August 8, 2007

Stretching: Is It Good Or Bad? You Decide

I've been looking for this for a while now. I get questions about stretching and exercise all of the time. "Doc, should I stretch before I workout, after I work out or what?".... For those other "docs", therapists and trainers out there, I'm sure you get queried the same as do I.

So, I dug back into my old computer files on a hard drive that has been taken out of service. Brushed off the dust and cob webs and found this from an August 2004 report. Let's see if this doesn't change your mind about pre-exercise or pre-competition stretching....Enjoy.

By the way, the info is out of Medicine and Sports & Exercise, a peer reviewed journal, and the commentary that followed is by Warren T. Jahn, DC, MPS, FACO, DACBSP, DABFPBoard Certified Chiropractic Orthopedist, Sports Physician & Forensic Examiner. Warren, thank you for all the work you do for our profession. It's guys and gals like you that make me proud.

Aug. 20, 2004 — Stretching impairs balance and worsens reaction and movement times, according to the results of a controlled study published in the August issue of Medicine & Science in Sports & Exercise. This could be problematic for elite athletes as well as for the elderly.

"Stretching is commonly utilized to increase the range of motion around the joint and theorized to improve athletic performance," write David G. Behm, PhD, from the Memorial University of Newfoundland in Canada, and colleagues. "A number of studies report that acute and prolonged stretching may actually reduce human performance through decreases in force and power."
To investigate the effect of acute lower-limb static stretching on balance, proprioception, reaction, and movement time, 16 subjects were tested before and after both a static stretching of the quadriceps, hamstrings, and plantar flexors or a control condition of similar duration. Five minutes of cycle warm-up preceded both the stretch and control conditions. In the stretch condition, subjects performed three 45-second stretches to the point of discomfort with 15-second rest periods for each muscle group. Outcomes included maximal voluntary isometric contraction (MVC) force of the leg extensors, static balance measured with a computerized wobble board, dominant lower-limb reaction and movement times, and the ability to match 30% and 50% MVC forces with and without visual feedback.

In the stretch and control conditions, decreases in MVC and ability to match submaximal forces were similar. Compared with the control condition, however, balance scores were worse in the stretch condition (9.2% vs 17.3%; P < .009). The stretch condition also resulted in prolonged reaction time (increase of +4.0% vs decrease of -5.8% for control) and movement time (+1.9% vs -5.7%; P < .01).

"It appears that an acute bout of stretching impaired the warm-up effect achieved under control conditions with balance and reaction/movement time," the authors write. "A warm-up consisting of general and specific activities related to the tasks may improve performance even after 20 minutes of recovery. Considering the minute differences between winning and losing in both individual and team sports as well as the precarious balance or stability of the elderly, the low but significant percentage changes in reaction time, movement time, and balance could result in serious consequences."
Med Sci Sports Exerc. 2004;36:1397-1402

Clinical Context: Stretching has been used to improve range of motion around joints and theorized to improve athletic performance. However, recent studies have not substantiated this claim. For example, Fowles and colleagues reported in the September 2000 issue of the Journal of Applied Physiology that stretching of a single muscle group for 15 to 30 minutes led to decreases in force and power attributable to impairments in neural output and changes in the musculo-tendinous unit (MTU). A more compliant MTU could alter reaction and movement times. Stretch-induced changes to either the afferent limb muscle responses or the mechanical output would affect the ability to adapt to stability changes, ie, balance.
The authors of this study postulated that even minor changes in reaction and movement times and balance associated with stretching could have important implications for athletic performance and rehabilitation. Instead of prolonged stretching of a single muscle group, as used in previous studies, the authors used an acute bout of static stretching on three lower-limb muscle groups to determine impact on reaction and movement times, balance, and strength in healthy male subjects.

Study Highlights:
16 healthy male subjects, mean age 24 years, weight 71 kg, and height 172 cm were selected to have pretest and posttest measurements before and after two interventions (stretching vs no stretching). Both interventions included a preintervention warm-up cycle of 5 minutes at 70 rpm on a cycle ergometer, submaximal and maximal leg extension contractions, 3 trials of rapid leg movement, and balance on a wobble board.

The active stretching intervention consisted of 3 stretches for 45 seconds each to the point of discomfort with 15-second rest periods for the quadriceps, hamstrings, and plantar flexors. The stretching lasted approximately 20 minutes in total.

The control intervention consisted of 20 minutes of rest. Pretesting and posttesting (each lasting 20 minutes) were conducted to measure the outcomes of (a) MVC force of the leg extensors, (b) static balance using a computerized wobble board, (c) movement and reaction times of the dominant lower limb, and (d) ability to match 30% and 50% MVC forces with and without visual feedback.

Day-to-day and test-retest reliability for the measurements ranged from 0.60 to 0.89. There was no significant difference in force output between the stretch and control interventions, with 6.9% and 5.6% decrement in force for the two interventions, respectively. There were no significant differences in the ability to match 30% and 50% MVC between the stretch and control interventions during the pretest and posttest. The control intervention resulted in a nonsignificant 18.8% and 10.7% greater accuracy for maintaining 30% and 50% MVC posttest.

Balance scores moved in opposite directions with the control intervention showing a significant improvement posttest (17.3% improvement; P < .05) and the stretch intervention showing a nonsignificant 2.2% decrease in balance score after stretching. The difference between the 2 interventions was significant at P < .009.

There were reverse trends for movement and reaction times for the two interventions. In the control group, both movement and reaction times improved posttest (5.8%; P = .16 for reaction time and 5.7%; P = .18 for movement time), whereas for the stretch intervention, movement and reaction times were nonsignificantly impaired by 4.0% and 1.9% poststretch, respectively.

Pearls for Practice:

  • Inserting a stretching routine within a rest period of a warm-up nullifies a small benefit in movement and reaction times and balance performance.
  • Stretching to the point of discomfort can adversely affect performance tests of static balance and movement and reaction times in healthy males.



The End...
Dr. Narson is a 2-term past president of the Florida Chiropractic Association’s Council on Sports Injuries, Physical Fitness & Rehabilitation and was honored as the recipient of the coveted Chiropractic Sports Physician of the Year Award in 1999-2000. He practices in Miami Beach, Florida at the Miami Beach Family & Sports Chiropractic Center; A Facility for Natural Sports Medicine.

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2 comments:

davidbaer said...

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Joanna said...

awesome information, thanks for sharing this. Time for the world to wake up and make changes in the way we exercise!!