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Effect of Acute Static Stretching on Force, Balance, Reaction Time, and Movement Time

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The purpose of the study was to investigate the effect of an acute bout of lower limb static stretching on balance, proprioception, reaction, and movement time. Sixteen subjects were tested before and after both a static stretching of the quadriceps, hamstrings, and plantar flexors or a similar duration control condition. The stretching protocol involved a 5-min cycle warm-up followed by three stretches to the point of discomfort of 45 s each with 15-s rest periods for each muscle group. Measurements included maximal voluntary isometric contraction (MVC) force of the leg extensors, static balance using a computerized wobble board, reaction and movement time of the dominant lower limb, and the ability to match 30% and 50% MVC forces with and without visual feedback. There were no significant differences in the decrease in MVC between the stretch and control conditions or in the ability to match submaximal forces. However, there was a significant (P < 0.009) decrease in balance scores with the stretch (decreasing 9.2%) compared with the control (increasing 17.3%) condition. Similarly, decreases in reaction (5.8%) and movement (5.7%) time with the control condition differed significantly (P < 0.01) from the stretch-induced increases of 4.0% and 1.9%, respectively. In conclusion, it appears that an acute bout of stretching impaired the warm-up effect achieved under control conditions with balance and reaction/movement time.
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Effect of Acute Static Stretching on Force,
Balance, Reaction Time, and Movement Time
DAVID G. BEHM, ANDREW BAMBURY, FARRELL CAHILL, and KEVIN POWER
School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John’s, Newfoundland, CANADA
ABSTRACT
BEHM, D. G., A. BAMBURY, F. CAHILL, and K. POWER. Effect of Acute Static Stretching on Force, Balance, Reaction Time, and
Movement Time. Med. Sci. Sports Exerc., Vol. 36, No. 8, pp. 1397–1402, 2004. Purpose: The purpose of the study was to investigate
the effect of an acute bout of lower limb static stretching on balance, proprioception, reaction, and movement time. Methods: Sixteen
subjects were tested before and after both a static stretching of the quadriceps, hamstrings, and plantar flexors or a similar duration
control condition. The stretching protocol involved a 5-min cycle warm-up followed by three stretches to the point of discomfort of
45 s each with 15-s rest periods for each muscle group. Measurements included maximal voluntary isometric contraction (MVC) force
of the leg extensors, static balance using a computerized wobble board, reaction and movement time of the dominant lower limb, and
the ability to match 30% and 50% MVC forces with and without visual feedback. Results: There were no significant differences in
the decrease in MVC between the stretch and control conditions or in the ability to match submaximal forces. However, there was a
significant (P0.009) decrease in balance scores with the stretch (29.2%) compared with the control (117.3%) condition.
Similarly, decreases in reaction (5.8%) and movement (5.7%) time with the control condition differed significantly (P0.01) from
the stretch-induced increases of 4.0% and 1.9%, respectively. Conclusion: In conclusion, it appears that an acute bout of stretching
impaired the warm-up effect achieved under control conditions with balance and reaction/movement time. Key Words: STABILITY,
ISOMETRIC FORCE, PROPRIOCEPTION, FLEXIBILITY
Stretching is commonly utilized to increase the range
of motion (ROM) around the joint (12,19) and theo-
rized to improve athletic performance (28). With the
exception of an increased ROM, recent studies have not
found substantial evidence to support the use of stretching
for improved performance. A number of studies report that
acute and prolonged stretching may actually reduce human
performance through decreases in force (4,14,15) and power
(11,40).
The stretch-induced decreases in force and power have
been attributed to impairments in neural output (2,4,13) as
well as changes to the musculo-tendinous unit (MTU)
(13,34). Fowles et al. (13) demonstrated an increase in
fascicle length of the soleus and lateral gastrocnemius of a
single subject with 30 min of stretching. Studies have re-
ported both decreases (24,35) and no change (23) in MTU
passive resistance or stiffness with stretching. MTU stiff-
ness incorporates the muscle, tendon, and other associated
connective tissue and can determine the effectiveness and
rapidity by which internal forces generated by the muscle
are transmitted to the skeletal system (38). Among the
functions of the intrafusal (includes stretch receptors) mus-
cle fibers, Golgi tendon organs and other proprioceptors is
to aid in the maintenance of balance (26) and detection of
the position of the body in space (proprioception) (8,10).
Acute changes in MTU length, stiffness, force output, and
muscle activation could alter the ability to detect (afferent
proprioception) and respond (efferent muscle activation) to
changes in the immediate environment. Stretch-induced im-
pairments might affect overall balance and stability or limb
proprioception. Furthermore, a more compliant MTU
(greater muscle and connective tissue slack) in conjunction
with a disturbed activation of the muscle could alter reaction
(RT) and movement (MT) times. There have been no studies
reporting on the effects of an acute bout of stretching on
balance, proprioception or reaction/movement time.
Balance involves the interaction of automatic postural
and voluntary motor commands of both the trunk and limb
musculature (6,30). Automatic postural responses are mod-
ulated by both trunk and leg inputs (5), with the central
nervous system (CNS) performing anticipatory postural ad-
justments when expecting self-inflicted postural perturba-
tions (1). Because under conditions of high instability the
CNS may suppress anticipatory postural adjustments, vol-
untary responses of trunk and limb muscles to postural
challenges would play a prominent role. Stretch-induced
changes to either the afferent limb muscle responses (pro-
prioception) or the mechanical output would be expected to
affect the ability to adapt effectively to stability challenges.
At the elite sport level, where milliseconds can mean the
difference between winning and losing, even small changes
in RT, MT, and balance can have a dramatic impact. For
example, differences between the personal best times of the
Address for correspondence: David Behm, Ph.D., School of Human Ki-
netics and Recreation, Memorial University of Newfoundland, St. John’s,
Newfoundland, Canada, A1C 5S7; E-mail: dbehm@mun.ca.
Submitted for publication December 2003.
Accepted for publication April 2004.
0195-9131/04/3608-1397
MEDICINE & SCIENCE IN SPORTS & EXERCISE
®
Copyright © 2004 by the American College of Sports Medicine
DOI: 10.1249/01.MSS.0000135788.23012.5F
1397
top sprinters in the world can differ by approximately 1%
(i.e., Greene: 9.79 s, Bailey 9.84 s, Christie: 9.87 s, Cason
9.92 s). Thus, even minor changes in RT, MT, and balance
could have important implications for athletic endeavors.
The possibility of stretch-induced impairments to balance,
RT, and MT not only affects sport applications but the loss
of dynamic balance is also a risk factor for osteoporotic
fractures (27). The contributions of RT and MT to dynamic
balance could have implications not only for athletes and
fitness enthusiasts but also for rehabilitation professionals
who prescribe stretching.
The objective of the present study was to examine alter-
ations in static balance, proprioception, RT and MT, and
force. It was hypothesized based on previous studies that
demonstrated decreases in force and activation as well as
changes in MTU stiffness that all the dependent variables
would be adversely affected by an acute bout of static
stretching.
METHODOLOGY
Approach to the problem and experimental de-
sign. Because a number of the previous studies investigat-
ing stretch-induced force and power decrements used pro-
longed stretching routines (1530 min) of single muscle
groups (4,13) that were not representative of typical stretch-
ing routines, the present study used a moderate volume of
stretching with three lower-limb muscle groups. Subjects
were tested before and after both an acute bout of static
stretching of the quadriceps, hamstrings, and plantar flexors
or a similar duration control condition. The stretching pro-
tocol involved a 5-min cycle warm-up followed by three
stretches to the point of discomfort of 45 s each with 15-s
rest periods for each muscle group (independent variable).
Measurements were conducted over a 20-min period that
included maximal voluntary isometric contraction (MVC)
force of the leg extensors, static balance using a computer-
ized wobble board, reaction and movement time of the
dominant lower limb, and the ability to match 30% and 50%
MVC forces with and without visual feedback (dependent
variables).
Subjects. Sixteen healthy male university students (age
24.1 7.4 yr, weight 71.5 15.4 kg, height 172.3
6.5 cm) volunteered for the experiment. All participants
were verbally informed of the protocol, and read and signed
a consent form. Each participant also read and signed a
Physical Activity Participation Questionnaire (PAR-Q: Ca-
nadian Society for Exercise Physiology) to ensure that their
health status was adequate for participation in the study. The
study was sanctioned by the Memorial University of New-
foundland Human Investigations Committee.
Intervention. Before stretching of both legs, subjects
performed a warm-up procedure consisting of a 5-min cycle
on a cycle ergometer (Monark Ergomedic 828E) at 70 rpm
with 1-kp resistance. The order of quadriceps, hamstrings,
and plantar flexors stretching was randomized. Stretches
were held to the threshold of discomfort for a duration of
45 s with 15-s recovery periods between stretches. Each
type of stretch was repeated three times. Stretching of both
legs included a series of unilateral kneeling knee flexion
(quadriceps), hip flexion with extended leg while supine
(hamstrings), extended leg dorsiflexion while standing
(stretch of the plantar flexors with gastrocnemius emphasis),
and flexed knee dorsiflexion while standing (stretch of the
plantar flexors with soleus emphasis). Stretching was pas-
sive for the quadriceps and hamstrings with the same re-
searcher controlling the change in the range of motion and
resistance for all subjects. The researcher would extend the
limb to the limits of the participants range of motion
without incurring injury. Subjects provided their own resis-
tance for the plantar flexors stretches with the instructions to
stretch the muscles to the point of discomfort.
For the control condition, subjects performed the 5-min
cycle warm-up and were allowed to rest for approximately
26 min between the pre- and posttesting periods. The 26-
min rest period provided similar pre- to posttest durations
for the stretching and control conditions. The order of con-
trol and experimental stretch conditions was randomized.
Testing. An orientation session involving multiple at-
tempts (minimum three attempts) for all measures was or-
ganized for all subjects 35 d before testing. The order of
testing was randomized. The stretching intervention com-
menced 2 min after the pretesting session. Postintervention
testing began within 1 min after the stretching routine. The
duration of pre- and posttesting was approximately 20 min
each.
For leg extension MVC force, subjects sat on a bench
with hips and knees flexed at 90°, and the upper leg and hips
restrained by two straps. The ankle was inserted into a
padded strap attached by a high-tension wire to a Wheat-
stone bridge configuration strain gauge (Omega Engineer-
ing Inc., LCCA 250). Prestretching, subjects performed two
leg extension MVC. If there was more than a 5% difference
in maximum force output, another MVC was performed.
Only two contractions were permitted poststretching to re-
duce the chance of fatigue. Three-minute rest periods were
allocated between contractions. The day-to-day reliability of
the strength test using an intraclass correlation coefficient
(ICC) was determined to be 0.9, with a between test (single
session) reliability of 0.93.
All torques were detected by the strain gauge, amplified
(Biopac Systems Inc., DA 100, and analog to digital con-
verter MP100WSW) and monitored on computer (Sona
Phoenix PC). All data were stored on a computer at a
sampling rate of 2000 Hz. Data were recorded and analyzed
with a commercially designed software program (Acq-
Knowledge III, Biopac Systems Inc.).
The matching force task used the same set-up as the MVC
test. Once the MVC force was established, grid lines were
provided on the computer, which outlined 30% and 50% of
the MVC force. Subjects were asked to exert sufficient
isometric leg extension force over a 5-s period to match the
gridlines. Visual feedback was always given for the first
three trials of a particular relative force (30% or 50% MVC),
while the computer screen was obstructed from view for the
subsequent three trials. Two-minute rest periods were per-
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Official Journal of the American College of Sports Medicine http://www.acsm-msse.org
mitted between attempts. The order of the relative force
matching tasks was randomized. The day-to-day reliability
of the matching force test using an ICC was determined
to be 0.8, with a between test (single session) reliability
of 0.88.
A balance ratio (contact with floor to no contact time) was
calculated by a software program (Innervations, Muncie,
IN) from a 30-s wobble board test (Kinematic Measurement
Systems, Muncie, IN). A metal plate connected to the com-
puter hardware was placed under the wobble board. When
the perimeter of the wobble board made contact with the
metal plate, the duration and frequency (during the 30-s test)
of contact was recorded by the software. Subjects received
an orientation session for the balance board on a separate
day as well as one to two practice attempts on the day of
testing. The day-to-day reliability of the balance test using
an ICC was determined to be 0.81, with a between test
(single session) reliability of 0.86.
RT and MT were measured by an apparatus developed by
the Memorial University of Newfoundland Technical Ser-
vices (Electronics, Newfoundland, Canada). The testing ap-
paratus consisted of a stop clock (58007, Lafayette Instru-
ment Company, Lafayette, IN), an analog timer (L15365/
099, Triton Electronics, UK), a stop clock latch (58027,
Lafayette Instrument Company) that connected the stop
clock and the analog timer, a custom-designed box (62 cm
(length) 15.5 cm (width) 9 cm (height)) with the
distance of 50 cm from center of start button to the center of
the stop button, and a trigger plate for the start of the task.
With the device situated on the floor, the task entailed
movement of the dominant foot in response to the illumi-
nation of an incandescent light bulb. The subject would start
with the nondominant foot on the floor and the dominant
foot (ball of foot) placed on the start button. Upon illumi-
nation of the light signal, the subject would release the start
button and move their foot forward to touch the stop button
(50 cm). RT was measured as the time between the illumi-
nation of light stimulus and release of the start button. MT
was measured as the time between the initiation of move-
ment and the depressing of the stop button. The actions
involved hip flexion, knee extension and plantar flexion. In
order to move as quickly as possible, the quadriceps and
plantar flexors would initiate the movement, while the ham-
strings would aid with the deceleration of the leg to accu-
rately touch the stop button. Three trials of RT and MT were
performed with 30-s rest periods. The day-to-day reliability
of the RT and MT tests using an ICC was determined to be
0.60 and 0.89 respectively with no significant (P0.05)
difference between values for test versus retest. Between
test (single session) ICC reliability measures of 0.79 and
0.93 were recorded for RT and MT, respectively.
Statistical analysis. Data were analyzed using a two-
way ANOVA repeated measures design. The factors in-
cluded condition (stretching vs control) and testing (pre- and
postcondition). An alpha level of P0.05 was considered
statistically significant. If significant differences (P0.05)
were detected, a Bonferroni-Dunns procedure was used to
identify the significant change. The means and SEM are
illustrated in Table 1. Reliability was assessed using an
alpha (Cronbach) model ICC (25) with all 16 subjects.
Repeated tests were conducted within 4872 h.
RESULTS
Overall, significant differences from the control condition
due to the stretching protocol occurred with measures of
static balance, RT and MT.
Force. There was no significant difference between
stretching and control conditions in force output. The stretch
and control conditions experienced similar 6.9% and 5.6%
force decrements, respectively, from the pretest to the
posttest.
Perceived force. Whether visual feedback was or was
not provided, there were no significant differences in the
ability to match 30% and 50% MVC between control and
stretch conditions during the pretest or posttests. The control
condition demonstrated a nonsignificant 18.8% and 10.7%
greater accuracy for maintaining 30% and 50% MVC
posttest.
Balance. Balance scores moved in opposing directions
resulting in a significant change (P0.009) for the pre- to
posttest differences between control and stretch conditions
(effect size 0.11: small). In comparison with the precon-
trol sessions, the control condition demonstrated a signifi-
cant (P0.05) 17.3% improvement in balance scores
postcontrol, whereas the stretch condition showed a nonsig-
nificant 2.2% decrease in balance scores poststretching rou-
tine (Table 1).
Reaction and movement time. Similar to balance
scores, reverse trends for the stretch and control conditions
resulted in significant change for the pre- to posttest differ-
ences with both reaction (P0.01, effect size 1.11:
TABLE 1. Balance, reaction and movement time data (means SEM).
Pretest Control
Condition
Posttest Control
Condition
Pre- to Posttest
Difference
Pretest Stretch
Condition
Posttest Stretch
Condition
Pre- to Posttest
Difference
Wobble board contacts 10.8 8.9 1.9 8.8 9.0 0.2
(2.0) (1.5) 917.3%* (1.7) (1.8) 82.2%
Reaction time (RT) 294 ms 277 ms 17 ms 283 ms 294 ms 11 ms
(27.5) (10.7) 95.8% (16.6) (15.8) 84.0%
P0.16
Movement time (MT) 427 ms 403 ms 24 ms 418 ms 426 ms 8 ms
(37.5) (30.2) 95.7% (32.6) (39.1) 81.9%
P0.18
* Asterisk indicates a significant difference from the pre-test condition. Significant differences were detected in the pre- to posttest differences between control and stretch conditions
for balance (power: 50%), RT (power: 95%), and MT (power: 50%).
STRETCHING EFFECTS ON BALANCE AND MOVEMENT Medicine & Science in Sports & Exercise
1399
moderate-large) and movement (P0.01, effect size
0.65: moderate) time, respectively (Table 1). In reference to
the pretest control session, RT and MT improved (de-
creased) by 5.8% (P0.16) and 5.7% (P0.18), respec-
tively. However, compared to the pretest stretch condition,
RT and MT were impaired (increased) by 4.0% and 1.9%
poststretch, respectively (nonsignificant).
DISCUSSION
The most important findings in this study were the im-
pairments in balance, RT and MT, due to prior stretching.
The control condition which involved a 5-min cycle warm-
up, submaximal and maximal leg extension contractions,
three trials each of rapid leg movement (RT and MT), and
balance on a wobble board followed by a 26 min rest period
improved performance in the balance, RT and MT tests.
Inserting a stretching routine within the rest period not only
nullified the beneficial effects of the warm-up but also
produced small performance decrements in relation to the
pretest scores.
These decrements reflect impairments associated with
recent studies that have reported stretch-induced decreases
in force (4,13,14), power (11,40), and muscle activation
(2,4,13). Although isometric forces decreased 6.9% after
stretching in the present study, the decrement was not sig-
nificantly greater than the 5.6% impairment in the control
condition. The lack of a significant loss of isometric force
may be attributed to the moderate volume of stretching
imposed. In contrast to other similar studies that have
stretched a single muscle group for 1530 min (4,13,14), the
present study involved only 135 s of intermittent stretching
for each of the three muscle groups.
Balance involves the interaction of automatic postural
and voluntary motor commands of both the trunk and limb
musculature (6,30). Balancing on a wobble board can in-
volve unanticipated perturbations to equilibrium that are
adjusted through contractions of both trunk and limb mus-
cles. Bloem and colleagues (6) speculated that lower leg
inputs act to modulate automatic postural responses. They
also found that the knees, hips, and trunk initiated move-
ment before the automatic postural responses. The CNS
performs anticipatory postural adjustments when expecting
self-inflicted postural perturbations (1). However, Aruin and
colleagues (1) suggested that under conditions of high in-
stability that the CNS may suppress anticipatory postural
adjustments as protection against their possible destabilizing
effects. Consequently, voluntary responses of trunk and
limb muscles to postural challenges would play a prominent
role. Shiratori and Latash (30) in a subsequent study from
the same laboratory reported that distal muscles (tibialis
anterior and soleus) cope with asymmetrical perturbations
and modulate the anticipatory postural adjustments in novel
situations (i.e., wobble board). Furthermore, Lipshits et al.
(22) described how perturbing balance by rapidly raising a
hand was initially counteracted by activation of lower limb
muscles. Therefore, it is apparent the important role that
lower limbs play in maintaining balance. Modifications to
either the afferent limb muscle responses or the mechanical
output would be expected to affect the ability of the periph-
eral neuromuscular system to adapt effectively to stability
challenges.
Stretching has been reported to alter the length and stiff-
ness of the affected limb MTU. Although the exact mech-
anisms responsible for increases in range of motion after
stretching are debatable, the increase is commonly attributed
to decreased MTU stiffness (37,39). Fowles et al. (13)
demonstrated an 8-mm increase in fascicle length of the
soleus and lateral gastrocnemius with 30 min of stretching.
Studies have reported both decreases (24,35) and no change
(23) in MTU passive resistance or stiffness with stretching.
Changes in MTU stiffness might be expected to affect the
transmission of forces, the rate of force transmission and the
rate at which changes in muscle length or tension are de-
tected. A more slack parallel and series elastic component
could increase the electromechanical delay by slowing the
period between myofilament crossbridge kinetics and the
exertion of tension by the MTU on the skeletal system. In
addition, the detection and monitoring of the muscle tension
by the Golgi tendon organs (GTO) would be delayed since
a more compliant tendon would not transmit the tension
information to the GTO as rapidly as a stiffer MTU. Fur-
thermore, increases in MTU length and decreases in MTU
stiffness could also alter the perception of the intrafusal
stretch receptors and thus perturb the afferent responses to
both changes in muscle length, rate of length change, and
tension (GTO). Therefore, stretch-induced changes in mus-
cle compliance might affect both the muscle afferent input
to the CNS and muscle output for counteracting unexpected
perturbations to balance.
Further evidence for the detrimental effect of an acute
bout of stretching on the CNS has been provided by Avela
et al. (2). They investigated the effects of passive stretching
of the triceps surae muscle on reflex sensitivity. After1hof
stretching, there were significant decreases in MVC
(23.2%), EMG (19.9%), stretch reflex peak-to-peak ampli-
tude (84.8%), and the ratio of H-reflex to muscle compound
action potential (M-wave) (43.8%). Although neural prop-
agation seemed unaffected (M-wave), afferent excitation of
the motoneuron pool (H-reflex) was impaired. They sug-
gested that the decrease in the excitation of the motoneuron
pool resulted from a reduction in excitatory drive from the
Ia afferents onto the
-motoneurons, possibly due to de-
creased resting discharge of the muscle spindles via in-
creased compliance of the MTU.
Stretch-induced impairments in RT and MT may be re-
lated to similar mechanisms as the disturbance in balance.
As mentioned previously, a more compliant MTU could
compromise the rate of tension development. Although it is
highly unlikely that the visual detection of the light stimulus
and the subsequent initiation of CNS motor programs to
move the leg would be adversely affected by stretching, a
prolonged electromechanical delay could negatively affect
both RT and MT. Although not monitored in the present
study, other studies have reported decreases in muscle ac-
tivation after stretching (2,4,13). Increases in motoneuron
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inhibition are more likely to affect the high-threshold fast-
contracting motor units that could also play a role in stretch-
induced RT and MT impairments.
An interesting development in the present study was the
control conditions improvements in balance scores, RT and
MT. This finding may provide support for the beneficial
effect of a short duration, combination of general (cycle
warm-up and leg extension contractions) and specific (pre-
test wobble board, RT and MT tests) activities. However,
because there was no condition in which a cycle warm-up
was not included, the contribution of the cycling cannot be
precisely deduced from the present study.
Young and Behm (41) reported similar results in a study
where subjects participated in five different warm-ups in a
randomized order before the performance of two jumping
tests. The warm-ups were: a) control, b) 4-min run, c) static
stretch, d) run and static stretch, and e) run and static stretch
and practice jumps. Generally, the stretching warm-up pro-
duced the lowest values and the run or run and stretch and
jumps warm-ups produced the highest values of explosive
force production. Thus, it should not be surprising that the
control conditions dynamic warm-up and static leg exten-
sion contractions facilitated subsequent performance.
Numerous studies have investigated the effects of ac-
tively warming-up on subsequent performance, yielding
mixed results. Although the majority of the research has
demonstrated that an increase in temperature facilitates hu-
man performance (9,29,32), other studies have shown in-
hibitory effects (5,16) as well as no effect (7) of warming-up
on subsequent performance. These conflicting results may
be attributed to discrepancies in the type of exercise, inten-
sity, duration, or any combination of these variables utilized
in the warm-up procedure. Studies have demonstrated that
warming-up can result in increased nerve conduction veloc-
ity (31). Increases in nerve conduction velocity could facil-
itate the response speed to perturbation in balance as well as
contributing to the improvements in RT and MT.
Another mechanism that may help explain the control
conditions improvement in RT, MT, and balance may be
the effect of postactivation potentiation (PAP). PAP can be
defined as an increase in the efficiency of the muscle to
produce submaximal force after a voluntary contraction.
PAP has been attributed to regulatory light chain (RLC)
phosphorylation (17,20,21,33), which increases the number
of force-producing crossbridges under conditions of subop-
timal Ca
2
activation (33). Suboptimal Ca
2
activation may
be present with lower-frequency stimulation such as the
lower-intensity contractions associated with static balance.
Potentiation also involves an increase in the rate constant of
crossbridge attachment (20). The increased rate constant
would allow a greater number of crossbridges to form dur-
ing a specific time period resulting in increased force and
rate of force development capabilities. Furthermore, at the
supraspinal level, motor-evoked potential facilitation has
been reported after different durations (5, 15, and 30 s) and
intensities (10%, 25%, and 50%) of thenar muscle voluntary
contractions (3). A number of studies have suggested that an
improved neuromuscular activation can occur after a few
MVC (18,40). Evidence of this postcontraction neural po-
tentiation is provided by increased H-reflex amplitudes (18)
that may persist for 10 min after the contractions (36). Thus,
pretest contractions in the control condition may have elic-
ited a PAP response providing both a facilitation of the
motoneuron excitation and RLC phosphorylation contribut-
ing to the significant improvements in RT and MT. Indi-
rectly, the PAP-induced augmentation of RT and MT would
also benefit balance by allowing more rapid responses to the
perturbations of the unstable environment. The stretching
condition may have nullified the beneficial effects of PAP
contributing to the 2.2% decrement in balance scores.
ICC (reliability) for the dependent measures were all in
the good to excellent category (0.800.93) except for the
day-to-day reliability of RT that scored 0.60 (moderate). A
paired samples t-test was then conducted on the RT mea-
sures. The lack of significant difference between the mea-
sures suggested that the low RT ICC may be attributed to the
low between subject variability. Another contributing factor
for this less than optimal reliability may be due to the test
set-up. The RT test for the lower limb necessitated that the
individuals place most of their mass on the nondominant
limb creating a degree of instability. Even with an orienta-
tion session, the lack of familiarity with this type of move-
ment and the greater instability may have led to a less
consistent action.
CONCLUSION
In summary, the findings of the present study demonstrate
that a moderate bout of stretching (three repetitions per
muscle group) held to the point of discomfort can adversely
affect performance on tests of static balance, RT and MT.
The stretch-induced impairments are hypothesized to be
related to changes in muscle compliance with the stretching
that may adversely affect the ability to detect and respond to
changes in muscle length, and rate of change in muscle
length and forces. Furthermore, it was found in the present
study that a warm-up consisting of general and specific
activities related to the tasks may improve performance
even after 20 min 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
RT, MT, and balance could result in serious consequences.
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STRETCHING EFFECTS ON BALANCE AND MOVEMENT Medicine & Science in Sports & Exercise
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Official Journal of the American College of Sports Medicine http://www.acsm-msse.org
... Unlike muscle strength and power, where a sort of consensus on the acute effect of SS exists [4], [10], the immediate effects of SS on dynamic balance, a key fitness component that contributes to injury prevention in a wide range of sports disciplines [7], including volleyball [22], has been a subject of significant contention [7], [10]. There are conflicting outcomes pertaining to the acute effects of SS on dynamic balance. ...
... For instance, Behm et al. [7] noted in their review that the acute effects of SS on balance remain inconclusive, yet consistent SS training could potentially enhance balance and contribute to mitigating the risk of falls and injuries. Additionally, Behm et al. [4] demonstrated that 3 sets of SS with 45 sec duration targeting the lower limbs resulted in reduced subsequent dynamic balance scores compared to the control condition in healthy male student. This is consistent with the results reported by Nagano et al. [31], who showed that dynamic balance performance was decreased after a single 3 min SS of the calf muscle in healthy physically active males. ...
... Unlike the frontal plane, short-duration SS does not yield any positive effect on dynamic balance in the sagittal plane among youth female athletes. Likewise, Behm, Bambury, Cahill and Power [4] noticed that the control groups (i.e., without stretching) showed a significant enhancement in balance, contrasting with the findings of Costa et al. [11], who reported no significant effects for the control groups. In contrast, our study reveals a different outcome regarding the impact of short-duration SS on postural balance concerning the body sway planes (i.e., FB or/and SB) on SPBB. ...
Article
Full-text available
Purpose The acute effects of static stretching (SS) on dynamic balance, a key fitness component that contributes to injury prevention, has been and is still a subject of significant debate. This study aimed to investigate the acute effect of short-duration SS exercises on dynamic balance following different recovery durations in youth female volleyball players. Methods Thirteen volunteers U-14 female players were included. Eight random assessments were carried-out on separate days. They consisted of 2D-kinematic analysis of frontal and/or sagittal balance of the center of mass (COM) displacement, velocity, and acceleration on wobble board conducted without SS, immediately after and following 2 and 10 minutes of SS. Results Repeated-measures ANOVA showed a significant difference between conditions in the velocity (p=0.002 to 0.049; d=0.844 to 2.200) and the acceleration (p=0.014 to 0.021; d=1.532 to 1.657) of the COM in both frontal and sagittal planes sway. Post-hoc analysis revealed decreased COM velocity (p=0.001 to 0.030; d=2.501 to 6.750) and acceleration (p=0.001 to 0.030; d=2.501 to 6.750) in the frontal plane, regardless of the recovery time. The most prominent decrease in both parameters was observed immediately after SS (p=0.001 to 0.013; d=2.907 to 6.750). However, in the sagittal balance, we observed an immediate increase in COM acceleration following SS (p<0.001; d=4.223). Conclusions Short-duration SS leads to improved dynamic balance, particularly on the frontal plane, with the most favorable effect observed immediately after stretching. Practically speaking, short-duration SS appears to be an effective exercise modality for inducing acute enhancements in dynamic balance among youth female volleyball players.
... All data were examined for normality using the Shapiro-Wilk test 18 because the sample size was < 30 subjects 36 . Data were deemed to be normally distributed if p > 0.05. ...
Article
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Benefits of neural mobilization (NM) have been described in musculoskeletal patients. The effects of NM on balance appear to be unclear in research, and no studies have tested the possible effects of NM on plantar pressures. Eighteen subjects were evaluated pre and post bilateral gliding of the sciatic nerve and its branches posterior tibial nerve, lateral dorsocutaneous, medial and intermediate dorsocutaneous nerves. Static variables of the plantar footprint and stabilometric variables were measured in a pre-post study. We found no differences in plantar pressure variables, Rearfoot maximum pressure (p = 0.376), Rearfoot medium pressure (p = 0.106), Rearfoot surface (p = 0.896), Midfoot maximum pressure (p = 0.975), Midfoot medium pressure (p = 0.950), Midfoot surface (p = 0.470) Forefoot maximum pressure (p = 0.559), Forefoot medium pressure(p = 0.481), Forefoot surface (p = 0.234), and stabilometric variables either, X-Displacement eyes-open (p = 0.086), Y-Displacement eyes-open (p = 0.544), Surface eyes-open (p = 0.411), Medium speed latero-lateral displacement eyes-open (p = 0.613), Medium speed anteroposterior displacement eyes-open (p = 0.442), X Displacement eyes-closed (p = 0.126), Y-Displacement eyes-closed (p = 0.077), Surface eyes-closed (p = 0.502), Medium speed latero-lateral displacement eyes-closed (p = 0.956), Medium speed anteroposterior displacement eyes-closed (p = 0.349). All variables don´t have significant differences however the measurements had a high reliability with at least an ICC of 0.769. NM doesn´t change plantar pressures or improve balance in healthy non-athletes subjects. NCT05190900.
... Assuming structural parameters such as muscle strength/size (2,15,16,88,89) or stiffness (15,16) as potential moderators for balance, recent reviews determined the used stretching intensity (24), weekly volume (duration per bout times frequency) (25) or supervision (110) to impact the stretch-induced effects. Therefore, the lack of significance could also be the result of low stretching intensities [e.g., stretching until point/sense of discomfort (62,67,75)], pain-free stretching (69), stretching until slight level of discomfort (71)), insufficient weekly volume [e.g., (78)] or frequency [e.g., (72,77)], insufficient intervention period [e.g., (64,76)] or performing stretching unsupervised [most did not state supervision, e.g., (69,71,73,76,78)], which could, in turn, be associated with insufficient intensity (110). In contrast, since Konrad et al. (32) did not find these parameters to affect stretching results on flexibility, it could be speculated that flexibility might not be the primary outcome to affect balance. ...
Conference Paper
Introduction One-third of individuals over the age of 65 fall at least once per year. Lacroix et al. (2017) shows that supervised strength training improves balance and muscle strength, which might beneficially impact the risk of falls. The American Geriatrics Society and the American Academy of Orthopaedic Surgeons recommend resistance training to improve balance (McMurdo, 2002). However, administrative burden such as limited mobility can reduce engagement among older adults for common training routines and call for the development of alternatives, but no review has investigated whether stretching has acute or chronic effects on balance. Purpose Since recent studies pointed out that high volumes of stretch could be used interchangeable with resistance training, but can be safely used without supervision (Warneke et al., 2024), this systematic review with meta-analysis investigate the effects of stretching on balance parameters across the lifespan. Methods PubMed, Web of Science, and Scopus were screened for (randomized) controlled trials (RCTs) on acute and chronic stretching effects, with subgroup analyses for a) stretching types, and b) different balance tasks, e.g., standing as still as possible on a force plate to measure the center of pressure (CoP) with eyes open (EO) and eyes closed, as well as Y-balance and star excursion test were conducted. We assessed risk of bias, while certainty of evidence was assessed in accordance with the GRADE working group guidelines. Statistical calculations were performed with R (version 4.2.3). Effect sizes (ES) were quantified using the packages Robumeta and Meta. Results Out of 18 acute studies, 15 compared acute stretching effects to passive control, while 4 performed comparisons to an active control, resulting in small magnitude effects on CoP/Sway EO (ES: 0.21, p = 0.03). Out of eleven chronic studies, seven had passive control, and 5 an active control group, resulting in moderate balance improvements with ES reaching 0.63, p = 0.04 for CoP/Sway EO. The remaining effects remained unsignificant (p = 0.091 - 1). Discussion While flexibility is commonly performed to enhance flexibility, it can also positively impact balance in some conditions. While our research question was derived via the positive association between strength and balance (Muehlbauer et al., 2015), and the possibility to use high volume stretching to enhance strength (Warneke et al., 2024), neither used included studies stretching durations of sufficient length, nor was strength measured as an outcome. It is noteworthy that most of the included studies did not interpret stretching effects in the light of underlying physiology, but on a more phenomenological basis, making a final conclusion about potential mechanisms complicated. Conclusion Although our results indicated beneficial effects of stretching on balance in some subgroup analyses, underlying mechanisms remain speculative, yet. There is a dearth of high-quality randomized controlled studies, using reasonable stretching times to enhance strength and muscle size via stretch to check whether there is the potential to use stretch-mediated hypertrophy and strength increases as a viable alternative to common resistance training and balance programs when aiming to enhance balance. References Lacroix, A., Hortobágyi, T., Beurskens, R., & Granacher, U. (2017). Effects of supervised vs. unsupervised training programs on balance and muscle strength in older adults: A systematic review and meta-analysis. Sports Medicine, 47(11), 2341–2361. https://doi.org/10.1007/s40279-017-0747-6 McMurdo, M. E. T. (2002). ‘Guideline for the prevention of falls in older persons’: Essential reading. Age and Ageing, 31(1), 13–14. https://doi.org/10.1093/ageing/31.1.13 Muehlbauer, T., Gollhofer, A., & Granacher, U. (2015). Associations between measures of balance and lower-extremity muscle strength/power in healthy individuals across the lifespan: A systematic review and meta-analysis. Sports Medicine, 45(12), 1671–1692. https://doi.org/10.1007/s40279-015-0390-z Warneke, K., Lohmann, L. H., Behm, D. G., Wirth, K., Keiner, M., Schiemann, S., & Wilke, J. (2024). Effects of chronic static stretching on maximal strength and muscle hypertrophy: A systematic review and meta-analysis. Sports Medicine – Open, 10, Article 45. https://doi.org/10.1186/s40798-024-00706-8
... Assuming structural parameters such as muscle strength/size (2,15,16,88,89) or stiffness (15,16) as potential moderators for balance, recent reviews determined the used stretching intensity (24), weekly volume (duration per bout times frequency) (25) or supervision (110) to impact the stretch-induced effects. Therefore, the lack of significance could also be the result of low stretching intensities [e.g., stretching until point/sense of discomfort (62,67,75)], pain-free stretching (69), stretching until slight level of discomfort (71)), insufficient weekly volume [e.g., (78)] or frequency [e.g., (72,77)], insufficient intervention period [e.g., (64,76)] or performing stretching unsupervised [most did not state supervision, e.g., (69,71,73,76,78)], which could, in turn, be associated with insufficient intensity (110). In contrast, since Konrad et al. (32) did not find these parameters to affect stretching results on flexibility, it could be speculated that flexibility might not be the primary outcome to affect balance. ...
Article
Full-text available
Introduction Balance is a multifactorial construct with high relevance in, e.g., everyday life activities. Apart from sensorimotor control, muscle strength and size are positively linked with balance performance. While commonly trained for via resistance training, stretch training has emerged as a potential substitution in specific conditions. However, no review has investigated potential effects of stretching on balance, yet. Methods PubMed, Web of Science and Scopus were searched with inception to February, 2024. Studies were included if they examined acute and/or chronic effects of any stretching type against passive and/or active controls on balance parameters – without any population-related restrictions concerning sex/gender, age, health status, activity level. Methodological quality was assessed using PEDro scale. Meta-analyses were performed if two or more studies reported on the same outcome. Certainty of evidence was determined based on GRADE criteria. Results Eighteen acute and eleven chronic effect studies were included. Stretching studies exhibited significant improvements for sway parameters with eyes open against passive controls of moderate magnitude for chronic (ES: 0.63, p = 0.047) and of small magnitude for acute studies (ES: 0.21, p = 0.032). Most other subgroups against passive controls as well as actively-controlled comparisons resulted in trivial and/or non-significant effects. Conclusion Even though some pooled effects slightly reached the level of significance, the overall results are biased by (very) low certainty of evidence (GRADE criteria downgrading for risk of bias, imprecision, publication bias). Moderators suggested by literature (strength, muscle size, flexibility, proprioception) were rarely assessed, which prevents conclusive final statements and calls for further, high quality evidence to clarify potential mechanisms–if any exist.
... Stretching itself enhances blood supply in joints and muscles, helping to warm them up, which improves functional performance during sports and activities of daily living (Savelberg and Meijer, 2003). Even though there is substantial evidence suggesting that stretching performed prior to physical activities may decrease muscle performance (Behm, Bambury, Cahill, and Power, 2004;Cramer et al., 2004;Cramer et al., 2007;Nelson, Guillory, Cornwell, and Kokkonen, 2001), they recommended a regular practice of static stretching due its satisfactory effect on flexibility as demonstrated in the present study. As important as stretching are the flexibility improvements acquired as a result of stretching training. ...
Book
This reference book contains information regarding the effectiveness of eccentric exercises and static stretching in improving calf muscle flexibility among male university students. The book presents data collected through original research and offers critical analysis. It will be beneficial for physiotherapists and individuals involved in physical education, aiding them in their research and academic endeavors. The research was conducted with a solid understanding of physiotherapeutic approaches, and the manuscript is written in clear and accessible language.
... According to Guissard and Duchateau (2004) and Weppler and Magnusson (2010), the impact of stretching exercises involves both mechanical factors (such as viscoelastic and plastic deformation of connective tissue) and nervous factors (including neuromuscular relaxation and modification of sensation). Dynamic stretching, among various warm-up techniques, has gained global popularity and is widely recommended (Behm et al., 2004). ...
Article
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The study aimed to compare the impact of warm-up with dynamic stretching (DS), warm-up with foam roller (FR), and warm-up with a combination of FR and DS (CO) on the performance of movement indicators in tests conducted on young volleyball players (n = 8, age = 15.4 ± 0.5 years, height = 176.3 ± 8.6 cm, weight = 64.5 ± 10.9 kg) during the competition year 2021/2022. To assess the effects of warm-up methods (DS, FR, CO), performance in various movement tests was compared. The tests included the sit and reach test (SR), a 1 kg ball throw in a kneeling position (H1), squat jump (SJ), countermovement jump (CMJ), sit-up test (SU), E-Test (ET), and run to cones (RC). The One-way ANOVA analysis did not reveal significant differences in the effects of DS, FR, and CO warm-ups (p > .05) across all investigated indicators. The effect size coefficient (η 2) indicated negligible differences (η 2 < 0.01), except for the ET indicator, where a small effect size (η 2 = 0.028, 95%CI: 0.04-0.31) favoured DS. These findings carry social importance as they contribute to enhancing the efficacy of warm-up routines, both in sports performance and health considerations.
... With a PEDro score of 3.95 § 0.67 (mean § SD) (score ranging from 2 to 6), risk of bias was rated as poor. Sixty-seven of 83 included studies randomly allocated participants into groups or the respective intervention sequence, 4 Table 2). ...
Article
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When recommending avoidance of static stretching prior to athletic performance, authors and practitioners commonly refer to available systematic reviews. However, effect sizes in previous reviews were in major parts extracted from studies lacking control conditions and/or pre-post testing designs. Also, currently available reviews conducted the calculations without accounting for multiple study outcomes, with effect sizes (ES)=-0.03 – 0.1 that would commonly be classified trivial. Since new meta-analytical software and controlled research articles arose since 2013, we revisited the available literature and performed a multilevel meta-analysis using robust variance estimation of controlled pre-post trials to provide updated evidence of the current state of literature. Furthermore, previous research described reduced EMG activity – also attributable to fatiguing training routines – as being responsible for decreased subsequent performance. The second part of this study opposed stretching and alternative interventions sufficient to induce general fatigue to examine if static stretching induces higher performance losses compared to other exercise routines. Including n=83 studies with more than 400 effect sizes from 2012 participants, our results indicate a significant, small ES for a static stretch-induced maximal strength loss (ES=-0.21, p=0.003), with high magnitude ES (ES=-0.84, p=0.004) for ≥60s stretching durations per bout when compared to passive controls. When opposed to active controls, the maximal strength loss ranges between ES=-0.17 – -0.28, p<0.001 – 0.04 with mostly no to small heterogeneity. However, stretching did not negatively influence athletic performance in general – neither when compared to passive nor active controls – while even a positive effect on subsequent jumping performance (ES=0.15, p=0.006) was found in adults. Regarding strength testing of isolated muscles (e.g., leg extensions or calf raises), our results confirm previous findings. Nevertheless, since no (or even positive) effects could be found for athletic performance, our results do not support previous recommendations to exclude static stretching from warm-up routines prior to, e.g., jumping or sprinting.
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Background Assessing the impact of cannabis on cognitive and physical performance is imperative, especially in safety-sensitive environments. This study investigated the degree and duration of performance impairment after cannabis consumption. Methods Fourteen cannabis users were subjected to physical and cognitive testing before and after smoking cannabis. Tests included assessment of intoxication, vital signs, psychomotor abilities, and muscle function. Blood, urine and saliva were analyzed for Delta-9-tetrahydrocannabinol (THC) and Carboxy-THC at baseline, and 1-, 6-, and 12-hours post-consumption. Results Blood THC levels peaked significantly at 1 hour and declined by 6 hours (p < 0.001), whereas Carboxy-THC levels showed a less pronounced but consistent variation over time (p = 0.005). Urine Carboxy-THC levels displayed a non-significant similar trend (p = 0.068). Acute cannabis use significantly (p = 0.01 – p < 0.001) raised systolic blood pressure and heart rate, increased force variability, reduced rate of force development, and compromised balance and muscle endurance up to 12 hours post-consumption. Conclusions Acute cannabis consumption results in physical impairments, impacting essential functions required for safety-sensitive tasks. The sustained presence of Carboxy-THC indicates prolonged pharmacological effects and necessitates cautious policy-making for workplaces. Trial Registration This study was not registered as a clinical trial as the ClinicalTrials.gov indicates that the study must answer yes to all four questions on their checklist. Although, our study was interventional, it was not conducted in the US nor involved a new FDA investigational new drug application, and the cannabis was not manufactured or exported from the US. The focus of the study was on the recreational use of a single cannabis cigarette on subsequent physiological or work performance and safety measures over 12 hours.
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Aim: The aim of the present study was to investigate the effect of proprioceptive exercises and massage on anaerobic performance and some physical fitness factors of women athletes. Methods: 28 women athletes with an average age of 24.8 ± 2.25 and weight of 60.02 ± 6.26 in four groups; the experimental group (1- massage, 2- proprioception exercises, 3- massage+ proprioception exercises) and the control group were randomly divided. In the pre-test session, all the subjects, with a four-minute warm-up in the form of jogging with an intensity of 30-40% HR, performed tests of anaerobic performance and some physical fitness factors and after a 72-hour washout period, the subjects started their activity for 12 minutes, each in their specialized group and according to the established protocol, and immediately the tests of the pre-test stage were repeated. A dependent t-test and one-way analysis of variance were used to analyze the data. Results: The results showed that the massage + proprioception group had a significant effect on the anaerobic peak power variable by 36.3%. All three groups of massage, proprioception, and massage +proprioception had a significant effect on the variables of average anaerobic power and fatigue index. In the variables of peak anaerobic power (p=0.001), average anaerobic power (p=0.011), fatigue index (p=0.016), and dynamic balance (p=0.015), there is a significant difference between the groups (p>0.05). Conclusion: In anaerobic activities, the use of proprioception exercises along with massage as part of warming up sports activities will most likely improve the performance of athletes.
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PQ] © by IAAF 11:4:67-81,1996 % ^ /n numerous sports and sport events performance is, to a great extent, determined by the level of speed-strength. An optimal preparation (worm-up) is necessary to achieve the highest possible realization of speed-strength in training and competition. Some top international athletes ore said to have produced the highest speed and speed-strength performances immediately after having performed a few Maximal Voluntary Contractions (MVCs). However, os yet no target-oriented and systematic studies of MVCs. as an element of warm-up programmes, have been conducted. Therefore the focus of the following study is on the following questions: (1) To what extent can the short-term potentia-tion of speed-strength induced by MVCs be considered us a general effect? (2) Can effects of post-tetanic potentiation be triggered in human beings by MVCs? (3) To what extent Is there a connection between possible short-term increases in speed-strength and neuronal effects of post-tetanic potentiation? The results of two complex training experiments show that MVCs carried out during the warm-up can really lead to a considerable increase In speed-strength performances of the lower extremities in alt athletics sprint and jumping events and of the upper extremities in the shot put and the throws, m ^ Dr Arne Gütlich was. from 1992 to 1996.
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AIthough intraclass correlation coefficients (lCCs) are commonIy used in behavioral measurement, pychometrics, and behavioral genetics, procodures available for forming inferences about ICC are not widely known. Following a review of the distinction between various forms of the ICC, this article presents procedures available for calculating confidence intervals and conducting tests on ICCs developed using data from one-way and two-way random and mixed-efFect analysis of variance models. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
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Sixteen experienced male powerlifters served as subjects in a training study designed to examine the effect of flexibility training on: (i) the stiffness of the series elastic components (SEC) of the upper body musculature and (ii) rebound and purely concentric bench press performance. Nine of the subjects participated in two sessions of flexibility training twice per week for 8 wk. Prior to and after the training period the subjects' static flexibility, SEC stiffness, rebound bench press (RBP), and purely concentric bench press (PCBP) performance were recorded. The flexibility training induced a significant reduction in the maximal stiffness of the SEC. Furthermore, the experimental subjects produced significantly more work during the initial concentric portion of the RBP lift, enabling a significantly greater load to be lifted in the post-training testing occasion. The benefits to performance achieved by the experimental group consequent to flexibility training were greater during the RBP lift as compared with the PCBP lift. The control subjects exhibited no change in any variable over the training period. These results implied that the RBP performance enhancement observed consequent to flexibility training was directly caused by a reduction in SEC stiffness, increasing the utilization of elastic strain energy during the RBP lift.
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Objective. —To determine how multiple risk factors for osteoporotic fractures could be modified by high-intensity strength training exercises in postmenopausal women.Design. —Randomized controlled trial of 1-year duration.Setting. —Exercise laboratory at Tufts University, Boston, Mass.Population. —Forty postmenopausal white women, 50 to 70 years of age, participated in the study; 39 women completed the study. The subjects were sedentary and estrogen-deplete.Interventions. —High-intensity strength training exercises 2 days per week using five different exercises (n=20) vs untreated controls (n=19).Main Outcome Measures. —Dual energy x-ray absorptiometry for bone status, one repetition maximum for muscle strength, 24-hour urinary creatinine for muscle mass, and backward tandem walk for dynamic balance.Results. —Femoral neck bone mineral density and lumbar spine bone mineral density increased by 0.005±0.039 g/cm2 (0.9%±4.5%) (mean±SD) and 0.009±0.033 g/cm2 (10%±3.6%), respectively, in the strength-trained women and decreased by -0.022±0.035 g/cm2 (-2.5%±3.8%) and -0.019±0.035 g/cm2 (-1.8%±3.5%), respectively, in the controls (P=.02 and.04). Total body bone mineral content was preserved in the strength-trained women (+2.0±68 g; 0.0%±3.0%) and tended to decrease in the controls (-33+77 g; -1.2%±3.4%, P=.12). Muscle mass, muscle strength, and dynamic balance increased in the strength-trained women and decreased in the controls (P=.03 to <.001).Conclusions. —High-intensity strength training exercises are an effective and feasible means to preserve bone density while improving muscle mass, strength, and balance in postmenopausal women.(JAMA. 1994;272:1909-1914)
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Reports 3 errors in the original article by K. O. McGraw and S. P. Wong (Psychological Methods, 1996, 1[1], 30–46). On page 39, the intraclass correlation coefficient (ICC) and r values given in Table 6 should be changed to r = .714 for each data set, ICC(C,1) = .714 for each data set, and ICC(A,1) = .720, .620, and .485 for the data in Columns 1, 2, and 3 of the table, respectively. In Table 7 (p. 41), which is used to determine confidence intervals on population values of the ICC, the procedures for obtaining the confidence intervals on ICC(A,k) need to be amended slightly. Corrected formulas are given. On pages 44–46, references to Equations A3, A,4, and so forth in the Appendix should be to Sections A3, A4, and so forth. (The following abstract of this article originally appeared in record 1996-03170-003.). Although intraclass correlation coefficients (ICCs) are commonly used in behavioral measurement, psychometrics, and behavioral genetics, procedures available for forming inferences about ICC are not widely known. Following a review of the distinction between various forms of the ICC, this article presents procedures available for calculating confidence intervals and conducting tests on ICCs developed using data from one-way and two-way random and mixed-effect analysis of variance models. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
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This study investigated the effects of preliminary exercise (warm-up) on glycogen degradation and energy metabolism during intense cycle ergometer exercise. After determination of VO2max, six male subjects were randomly assigned to perform warm-up (WU) and no warm-up (NWU) trials incorporating a 2 min standardized sprint ride (SR) at 120% of the power output attained at VO2max (POmax). Muscle biopsies and temperature (Tm) recordings were obtained from the vastus lateralis muscle. Tm was elevated above the resting level prior to the SR during the WU trial (37.7 +/- 0.1 vs 35.4 +/- 0.4 degrees C; P less than 0.05) and remained higher than the NWU trial after the SR (38.6 +/- 0.2 vs 37.1 +/- 0.4 degrees C; P less than 0.05). Similar trends existed for rectal temperature (Tr). The increases in Tm and Tr during the SR were both greater in the NWU trial (P less than 0.05). Muscle glycogen degradation was similar for the WU and NWU trials (30.8 +/- 3.7 vs 25.6 +/- 3.7 mmol.kg-1, respectively). When blood and muscle lactate concentrations after the SR were expressed relative to values before the SR, the WU trial resulted in a lower accumulation of blood lactate (6.5 +/- 0.9 vs 10.7 +/- 0.8 mEq.l-1; P less than 0.01) and muscle lactate (20.1 +/- 0.1 vs 23.4 +/- 2.2 mEq.kg-1 wet wt.; P less than 0.05). Furthermore, oxygen consumption during the 1st min of the SR was higher in the WU trial (2.3 +/- 0.2 vs 1.9 +/- 0.2 l.min-1; P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)