Effects of Stretching on Strength
215
contraction). In contrast to these results, other au-
(15 or 30 seconds) did not influence the degree of
force loss following static stretching.
thors
[35-40]
did not observe any detrimental effects of
stretching on strength. The total stimuli duration in
1.2 Effects on Jumping Performance
these studies was shorter, ranging from 30 to 480
seconds. Bandeira et al.
[41]
did not observe decreases
Several studies have investigated the acute effect
in strength performance of ballet dancers when us-
of stretching exercises on vertical jump perform-
ing 15 seconds of static active stretching exercises,
ance. Church et al.
[48]
reported a significant decrease
with a total of 90 seconds stretching. On the other
in performance when this was preceded by PNF
hand, when using 60 seconds for each exercise (360
stretching, but not by static stretching. This confirms
seconds total stimuli), performance of the hip flex-
the findings of Power et al.
[22]
and Knudson et al.,
[49]
ors was decreased, but not that of the hip extensors
who investigated the effects of static stretching and
(table I).
also found no significant decreases in vertical jump
performance. On the other hand, two studies did not
Most studies showed decreases in strength per-
find decreases in vertical jump performance in
formance when preceded by stretching exercises.
trained women either after PNF stretching
[50]
and
However, it should be noted that these studies used
following static or ballistic stretching.
[51]
Other stud-
more than one stretching exercise for the same mus-
ies found decreases in vertical jump performance
cle group and/or the number of sets and the duration
after static stretching,
[52-55]
ranging from 4.5% to
of stretching were greater than the ranges normally
7.3% and 3.2% to 4.4% with and without
recommended in the literature and used in sporting
counter movement, respectively (table II).
activities. It has been recommended that four sets of
Muscular strength is one of the most important
stretching is performed for each muscle group,
[42]
factors in performing the vertical jump. If stretching
with 1030 seconds duration in each stretched posi-
has the acute effect of reducing performance in
tion.
[42-46]
For individuals >65 years of age, a longer
strength, it would be expected to reduce that of
duration of 60 seconds should be used.
[47]
Therefore,
jumping as well. In practice, this information is
it is possible that the total stretching duration may
highly important for sporting events in which
have been excessively long in the studies showing
strength and jumping performance are fundamental,
decreases in strength performance.
since a decrease in performance may hinder the final
Data from our laboratory
[21,25]
showed 8.9% and
result. It is possible that conflicting results could be
12.3% reductions in hip adductor isometric strength
explained by the different methods used for stretch-
ing or by the absence of information regarding relia-
measured at 45
°
, and 10.4% and 10.9% at 30
°
fol-
bility and precision of these methods. Therefore, it is
lowing four 30-second sets of static or PNF (`con-
clear that this subject deserves further investigation.
tract-relax' technique) stretching, respectively. De-
In addition, studies investigating the chronic effect
creases in strength after static stretching in knee
of stretching on jump performance are also required.
flexion and extension were 9.9% and 2.3%, and
decreases after PNF were 11.4% and 4.8%, respec-
2. Chronic Effects of Stretching on
tively. These findings concur with the evidence that,
Strength Performance
even with a total stretching time following the litera-
ture recommendations and with only one exercise
Very few studies have looked into the chronic
for each muscle group, a significant decrease in
effects of stretching on strength performance. Wor-
strength performance may still take place. Interest-
rel et al.
[56]
used static and PNF `contract-relax'
ingly, the deleterious effect of stretching on strength
methods to train the flexibility of the hamstrings;
performance seems to occur even with experienced
exercises were performed five times a week, for 3
stretchers, as evidenced by Nelson et al.
[23]
Recent-
consecutive weeks, totaling 15 sessions with 20
ly,
[29]
it was shown that the duration of the stimuli
minutes per method, per session. Handel et al.
[57]
2007 Adis Data Information BV. All rights reserved.
Sports Med 2007; 37 (3)
Study 