Page 123 - Journal of Special Operations Medicine - Summer 2015

Figure 1 Associations between flexibility and injuries. Figure 2 Associations between stretching and injuries.
(A) Recruits in US Army Infantry One-Station Unit Training. (A) Runners. (B) Recruits in Australian Basic Training.
(B) SEAL candidates. PT, physical training.

the lower body prior to running, and one group did to activity reduced performance on both strength and
not perform any stretching. The group that stretched power tasks regardless of age, sex, or training status.
received training in proper stretching techniques before Smaller negative effects were noted with shorter periods
the study began. After 16 weeks of training, the injury of stretching.
incidence in the two groups was almost identical and
there were no significant difference between the groups It would appear that either too much or too little flex-
(Figure 2A). Another study was conducted among ibility is associated with higher injury risk and that
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1,538 male recruits in Australian basic training that static stretching has little effect on overall injury risk.
were separated into two groups. One group performed In studies where all participants perform stretching,
one 20-second static stretch for six major leg muscles there will likely be a variety of “natural” flexibilities
prior to physical training, while the other group did not (i.e., flexibilities before stretching) ranging from low to
perform any stretching. The data were calculated based high. Those with low flexibility will increase their flex-
on the number of injuries per 1,000 hours of physical ibility with stretching. This may be equivalent to mov-
training. There was no significant difference between ing from Q1 to Q2 or Q3 in Figure 1A. Those who are
the two groups whether the authors looked at all in- more flexible will also further increase their flexibility
juries, soft tissue injuries, or bone injuries (Figure 2B). and may move from Q4 to Q5, or even off the chart.
It may appear that soft-tissue injuries were somewhat It may be that individuals with low flexibility need to
reduced in the group that stretched; however, it can be be identified and provided stretching exercises, while
calculated that with a difference of the size seen in Fig- those who are highly flexible do not need to stretch. We
ure 2B, and assuming 1-hour physical training sessions, do not really know at this point, but studies conducted
a recruit would need to stretch for 1,666 sessions to along these lines could test this hypothesis. Currently,
prevent one injury of this type. Another study, with the the data suggests that when large groups of individuals
Japan Ground Self-Defense Force, found that stretching perform static stretching the overall risk of injury does
had no effect on overall injury incidence but might re- not change compared to no stretching at all. Further,
duce muscle/tendon injury. Literature reviews of stud- acute stretching may be detrimental to activities involv-
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ies on static stretching have generally concluded that ing strength and power. Soldiers should keep in mind
stretching prior to exercise does not reduce the over- that flexibility is a component of physical fitness and
1
all incidence of injuries, but further research is needed that stretching does increase flexibility. Just because
4,5
on examining particular types of injuries, like muscle static stretching has little effect on overall injury risk
strains. 5,10 does not mean that it should not be performed at all.
Stretching may be included at the end of an exercise
Besides the futility of stretching to prevent injuries, it ap- period when the body is warmed up from the activity.
pears that stretching may be detrimental for some types Those who are very flexible may not need to stretch,
of performances. Meta-analysis is a statistical technique but more research is needed on this. It is only acute
that allows data from multiple studies to be combined stretching that affects strength and power and so
to more adequately determine how large a particular ef- stretching at the end of an exercise bout should not af-
fect might be. A recent meta-analysis examined 104 fect later activities unless those activities are performed
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studies that looked at the effect of pre-exercise stretch- immediately after exercise. Currently, stretching after
ing on maximal strength and power (the authors called exercise is recommended in the Army’s Physical Readi-
the latter “explosive strength”). Static stretching prior ness Training Program. 12

Physical Fitness for Injury Prevention 113