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Warren B. Young, PhDUniversity of BallaratBallarat, Victoria, AustraliaDavid G. Behm, PhDMemorial University of NewfoundlandSt. John’s, Newfoundland, CanadaKeywords: warm-up; static stretching; strength and power.WARM-UP BEFORE PHYSICALactivity is a universally acceptedpractice with the objective ofpreparing the athlete physicallyand mentally for optimum perfor-mance and is believed to reducethe risk of injury and enhanceperformance (15, 25). Warm-upstypically contain 3 components:• A relatively low-intensity aero-bic component that is generalin nature such as submaxi-mum running. The rationalegiven for this is that it increas-es core and muscle tempera-ture, which improves neuro-muscular function (15, 22, 28).• Some stretching of the specificmuscles involved in the subse-quent activity. Some athletesmay spend 30 minutes orlonger systematically stretch-ing each muscle group. Thereare many variations of stretch-ing protocols such as proprio-ceptive neuromuscular facili-tation (PNF), static, anddynamic methods. Thesemethods are outlined thor-oughly in texts such as Alter(1) and Norris (22) and will notbe discussed in detail in thisstudy. Although the optimummethod for increasing flexibili-ty over a relatively long timemay be debatable, passive stat-ic stretching remains a popu-lar method used in a pre-exer-cise or precompetition warm-up routine. This usually in-volves moving a limb to the endof its range of motion (ROM)and holding it in the stretchedposition for 15–60 seconds(22). The objective of stretchingin a warm-up is usually toachieve a short-term increasein the ROM at a joint (8, 15,22) or to induce muscle relax-ation and therefore decreasethe stiffness of the muscle-ten-don system (7, 22).• Rehearsal of the skill about tobe performed. This is usuallyperformed at gradually in-creasing intensities, culminat-ing in some efforts that areequal to or greater than theexpected competition intensi-ty. This type of warm-upserves to activate or recruit thespecific muscle fibers andneural pathways required toachieve optimum neuromus-cular performance (15).Although the need for a warm-up before maximum effortstrength and power exercise israrely questioned, the precise pro-tocol leading to optimum perfor-mance is not well established. Thepurpose of this article is to discusswarm-up and, in particular, to re-view recent research that ques-tions the traditional use of staticstretching in a warm-up beforestrength and power activities. Forthe purpose of this discussion,strength is defined as the maxi-mum force produced in a staticmaximum voluntary contraction,relatively slow isokinetic contrac-tion, or the maximum weight lift-ed in a 1 repetition maximum test.Power activities are considered tobe any movements requiring sig-nificant amounts of both force andspeed, such as a vertical jump.
December 2002 Strength and Conditioning Journal 33
© National Strength & Conditioning Association
Volume 24, Number 6, pages 33–37
Should Static Stretching Be
Used During a Warm-Up for
Strength and Power Activities?
Warren B. Young, PhD
University of Ballarat
Ballarat, Victoria, Australia
David G. Behm, PhD
Memorial University of Newfoundland
St. John’s, Newfoundland, Canada
Keywords: warm-up; static stretching; strength and power.
activity is a universally accepted
practice with the objective of
preparing the athlete physically
and mentally for optimum perfor-
mance and is believed to reduce
the risk of injury and enhance
performance (15, 25). Warm-ups
typically contain 3 components:
A relatively low-intensity aero-
bic component that is general
in nature such as submaxi-
mum running. The rationale
given for this is that it increas-
es core and muscle tempera-
ture, which improves neuro-
muscular function (15, 22, 28).
Some stretching of the specific
muscles involved in the subse-
quent activity. Some athletes
may spend 30 minutes or
longer systematically stretch-
ing each muscle group. There
are many variations of stretch-
ing protocols such as proprio-
ceptive neuromuscular facili-
tation (PNF), static, and
dynamic methods. These
methods are outlined thor-
oughly in texts such as Alter
(1) and Norris (22) and will not
be discussed in detail in this
study. Although the optimum
method for increasing flexibili-
ty over a relatively long time
may be debatable, passive stat-
ic stretching remains a popu-
lar method used in a pre-exer-
cise or precompetition warm-
up routine. This usually in-
volves moving a limb to the end
of its range of motion (ROM)
and holding it in the stretched
position for 15–60 seconds
(22). The objective of stretching
in a warm-up is usually to
achieve a short-term increase
in the ROM at a joint (8, 15,
22) or to induce muscle relax-
ation and therefore decrease
the stiffness of the muscle-ten-
don system (7, 22).
Rehearsal of the skill about to
be performed. This is usually
performed at gradually in-
creasing intensities, culminat-
ing in some efforts that are
equal to or greater than the
expected competition intensi-
ty. This type of warm-up
serves to activate or recruit the
specific muscle fibers and
neural pathways required to
achieve optimum neuromus-
cular performance (15).
Although the need for a warm-
up before maximum effort
strength and power exercise is
rarely questioned, the precise pro-
tocol leading to optimum perfor-
mance is not well established. The
purpose of this article is to discuss
warm-up and, in particular, to re-
view recent research that ques-
tions the traditional use of static
stretching in a warm-up before
strength and power activities. For
the purpose of this discussion,
strength is defined as the maxi-
mum force produced in a static
maximum voluntary contraction,
relatively slow isokinetic contrac-
tion, or the maximum weight lift-
ed in a 1 repetition maximum test.
Power activities are considered to
be any movements requiring sig-
nificant amounts of both force and
speed, such as a vertical jump.
34 Strength and Conditioning Journal December 2002
Static Stretching in the
Although static stretching has
been found to be effective in caus-
ing an acute increase in the ROM
at a joint (1, 11, 17, 30), research
indicating that static stretching
can also produce a significant
acute decrement, of approximate-
ly 5–30%, in strength (2, 6, 12, 18,
19) and power production (4, 5,
16, 31, 32) of the stretched muscle
groups has accumulated. These
findings have led some researchers
to recommend against the practice
of stretching before strength or
power activities (4, 16). But it is
not clear whether the detrimental
effects of stretching used in sever-
al studies could have a negative ef-
fect on strength and power perfor-
mance in athletes because the
protocols used were not represen-
tative of the typical warm-up meth-
ods used by athletes to prepare for
exercise or competition. For exam-
ple, stretch treatments of 15-
minute duration or longer have
been used for a single muscle
group (2, 6, 12), which is a greater
duration than that commonly used
by many athletes for stretch treat-
ments. Furthermore, some studies
observed performance decrements
after stretching—when there was
no aerobic component or submax-
imum exercise preceding the
stretching (4, 6, 12, 18, 19) or
when there were no practice trials
of the test activity (2–4, 6, 18, 19).
Although this research design is
necessary to isolate the influence
of stretching, it is possible that the
aerobic or low-intensity exercise
and practice components of a
warm-up may offset any potential
negative effects of stretching. For
example, a study by Knudson et al.
(10) reported a nonsignificant de-
crease in vertical jump perfor-
mance after a static stretching
routine. Fifty-five percent of the
subjects experienced a decrease in
performance, whereas other sub-
jects either experienced no change
or an increase in performance
after stretching. In this study the
participants performed 3 minutes
of submaximum cycling and 3
practice vertical jumps before the
stretching. It is possible that for
45% of the subjects who exhibited
no decrease in performance, the
cycling and practice jumps had a
positive effect.
A recent study has attempted
to identify the influence of sub-
maximum running, static stretch-
ing, and practice jump that are
components of a warm-up (31).
On the basis of a test of concentric
vertical jump height, 4 minutes of
running was significantly better
than a control warm-up, and run-
ning plus 4 minutes of total
stretching of the quadriceps and
gluteals was significantly worse
than just running. Furthermore,
running plus stretching plus 4
practice jumps was significantly
better than the running plus
stretching warm-up. These results
suggest that stretching produced
a negative effect, whereas the run
and the practice jumps produced
positive effects in the warm-up for
vertical jumps. Unfortunately, the
study did not examine the effect of
a run plus practice jumps warm-
up, which may be expected to pro-
duce the best results. This study
supports previous research and
indicates that in more realistic
athletic warm-up conditions, as
little as 2 minutes of static
stretching per muscle group can
impair power performance.
Mechanisms of Stretch-
Various authors have speculated
about the mechanism that explains
the impairment of muscle force.
Neural inhibition (2, 6, 29) and in-
creased muscle-tendon compliance
leading to a reduced rate of force
transmission from the muscle to
the skeletal system (4, 12, 18, 19)
have been suggested as possible
mechanisms. Because static
stretching can significantly in-
crease muscle soreness and mus-
cle damage, as indicated by elevat-
ed creatine kinase in the blood (27),
tissue damage is another possibili-
ty to explain acute performance
decrement. But the precise mecha-
nism(s) that leads to stretch-in-
duced reductions in strength and
power is not clear (2, 6).
There is some evidence that
the impairment may be concen-
trated and related to certain joint
angles (18), contraction types (5,
32), or contraction velocities (19).
It has also been shown that ballis-
tic stretching can inhibit strength
(20), and a PNF stretch protocol
produced a greater negative effect
on vertical jump performance
than that produced after a static
stretch warm-up (3), but consid-
erably more research is required
to clarify the precise stretching
protocols that produce an effect
and the performance conditions
that are most affected.
Stretching and Injury
The question that follows is:
should static stretching be elimi-
nated from a warm-up before
strength and power activities? To
answer this, the negative effects
should be weighed against the po-
tential injury prevention benefits
of static stretching. It has been
traditionally believed that static
stretching reduces the risk of
muscle-tendon injury; however,
there is mounting evidence to the
contrary (9, 26). For example,
Pope et al. (23) reported in a large
prospective study that stretching
in a warm-up did not significantly
December 2002 Strength and Conditioning Journal 35
reduce the risk of injury in army
recruits undergoing high-intensi-
ty training.
It is clear that static stretching
is effective in causing an acute in-
crease in the ROM at a joint (stat-
ic flexibility) (1, 17, 30). It is not so
clear whether submaximum exer-
cise, e.g., running, cycling, in-
creases ROM (17, 30). But it is
thought that the injury prevention
benefit of warm-up resides in a
short-term reduction in muscle
stiffness rather than simply in-
creased joint ROM (7, 8). Reduced
stiffness is associated with less re-
sistance (force) to stretch when the
muscle is relaxed (passive stiff-
ness) so that there is less likeli-
hood of damage when the muscle
is elongated (7). Static stretching
has been found to reduce passive
muscle-tendon stiffness for up to 1
hour (13, 14), but a reduction has
not always been found (30). Fur-
thermore, when muscle-tendon
stiffness is measured during mus-
cle contraction (active stiffness), it
has been found to be unaffected by
stretching (8, 17). In contrast, 10
minutes of running has been
found to be effective for reducing
the active stiffness of the calf mus-
cles (17). Increased muscle tem-
perature has been shown to in-
crease the resistance to muscle
tear (21, 25). Therefore, if active
rather than passive stiffness is re-
lated to injury risk, this suggests
that increasing muscle tempera-
ture by submaximum exercise
would be more important than
stretching for decreasing the risk
of soft tissue injury (9). But the ef-
fect of running and stretching on
passive and active muscle-tendon
stiffness and injury prevention in
general is still unclear (9).
Summary and Practical
Substantial evidence is now avail-
able to state that static stretching
can impair strength and power
performance, although the dura-
tion of the impairment, the exact
stretching protocols, and the
physiological mechanisms are not
yet known. Given the lack of evi-
dence in favor of static stretching
during warm-up for injury pre-
vention, it seems justifiable to ex-
clude this component from the
warm-up for strength and power
activities. Progressive submaximal
exercise intended to increase
muscle temperature and practice
trials of the ensuing activity
should be retained.
Some coaches have replaced
static stretching with dynamic ac-
tivities. For example, Rutledge and
Faccioni (24) outlined warm up
activities for field hockey that con-
sisted of running drills that isolat-
ed various joints and were per-
formed with gradually increasing
intensity. When an athlete per-
forms run-throughs at progres-
sively increasing intensities, the
joints are taken to a new ROM;
therefore, the muscles are being
stretched dynamically. Whether
such a dynamic warm-up has the
same effect as static stretching for
increasing ROM or influencing the
injury risk is not clear, but is wor-
thy of examination. Further ex-
perimentation is needed before the
optimum warm up protocol can be
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December 2002 Strength and Conditioning Journal 37
Warren Young, is Senior Lecturer
with the School of Movement and
Sport Sciences at the University of
Ballarat in Victoria, Australia.
David G. Behm, is an associate
professor in the School of Human
Kinetics and Recreation at Memo-
rial University of Newfoundland.
... The research suggests that static stretching is acutely detrimental to muscular performance. On the other hand, static stretching has been shown over time to increase range of motion, and overall strength throughout a full range of motion for better functionality (Young & Behm, 2002). Thus, the benefits of static stretching cannot be entirely overlooked. ...
... The overall consensus is that a warm-up using static stretching, is detrimental to performance for activities that are dependent on higher velocities and power for successful performance (Fradkin et al., 2010;Young & Behm, 2002;Talpey et al., 2014;Andre et al., 2014). ...
Full-text available
Warm-ups are an essential element of exercise and sport performance. Although research has demonstrated benefits associated with active warm-ups, research investigating the effects of a passive warm-up on subsequent performance is limited. The purpose of this study is to compare the effects of an active, post-activation potentiation (PAP) warm-up to a passive warm-up on vertical jump performance. Study participants were randomly assigned to one of two groups. Each group performed both the active and passive warm-ups, in reverse order, to control for order effect. Participants in this study consisted of 20 college students (men and women) between the ages of 18 and 35 years who were well-trained and anaerobically fit. A repeated measures ANOVA revealed a statistically significant main effect difference in vertical jump measures (F=16.148, p<0.001). Further analysis of the results demonstrated that between the three treatments tested, control, active, passive, there was a statically significant difference between the active warm-up when compared to both the passive and control warm-ups (p=0.004; p<0.001). The results also indicated that there was practical significance between the active and passive treatment as well as the control group (partial eta squared=0.459). In conclusion, an active warm-up prior to vertical jump testing appears to be superior to a passive warm-up. Physiologically the body may perform better following dynamic movements rather than through a passive increase in intramuscular temperature. Prior to athletic events, we recommend athletes perform warm-ups utilizing dynamic movements rather than using a heating system alone.
... The warm-up is a phase prior to the actual beginning of a music lesson, or choir rehearsal; it is made up of a series of teacher-lead tasks and exercises, and, which also includes some stretching and relaxation exercises (Young and Behm, 2002;Bishop 2003, Asztalos, 2018, like breathing, 'buzzing' , practicing short descending and ascending scales by singing a variety of syllables and texts. (Hylton, 1995;Collins, 1999;Asztalos, 2018). ...
... In sports especially volleyball during the warm up even today static stretching inserted between the general and specific part (Young &Behm, 2002), because the static stretching is considered a key component improving flexibility ( (Worrell, Smith, &Winegardner, 1994), the prevention of muscle injury (Safran, Seaber, & Garrett, 1989), and the reduction of muscle injury (Smith, 1994). These improvements contribute to flexibility the performance of game movements with biomechanical precision providing production of maximum forces across the range of kinematic joints (Van Gyn, 1986). ...
Full-text available
The purpose of this study was to investigate the effect of static stretching on kinematics characteristics of female volleyball players during the initial part of the movement of the attack spike from the back row defense, in position 1. Twelve female volleyball players (age 18-21, training age 6-10 years, height 178.17 ± 3.15 cm and weight 65.90 ± 5.80 kg), volunteered as participants and they were randomly divided into two groups of 6 players. The exercise protocol involved a 5 minutes general warm-up, followed by the initial attack spike. After the first measurement, participants execute static stretching of the upper limbs and the final spike. Kinematic characteristics of the players during the initial and final spike, divided into 2 times (T) and 1 phase, were evaluated by a three-dimensional (3D) vinteoanalysis APAS. Paired t-test and Wilcoxon analysis showed significant difference and increase after the static stretching, of the right wrist displacement (DRWr) at the T 2 and 4 (p=0.014, p=0.039), of the left wrist displacement (DLWr) at the T 3 (p=0.012) and of the right wrist range of motion (RomRWr) at the first phase (p=0.037). Significant difference and reduction, after the static stretching, was found of the left shoulder angular velocity (VLSh) at T 4 (p = 0.024) and of the right wrist (VRKarp) at T 4 (p = 0.008, p = 0.017). No difference was observed on the kinematics characteristics of the lower limbs, on the total displacement (D) and the velocity of the center of body mass (CM), on the jump height and the speed of the ball. It is concluded that the volleyball players should avoid static stretching before the competition. ABSTRACT
Full-text available
Foam roller exercises are frequently used in training, especially during the warm-up phase. The aim of this study is to examine the acute effects of foam roller exercises performed only on the calf, quadriceps or gluteus maximus muscles on vertical jump performance and the time-course changes of these effects. In this study, 23 males participated voluntarily. The study was carried out using the crossover experimental design. In this study, the participants performed foam roller exercises on the calf, quadriceps, and gluteus maximus muscles on separate days. Foam roller exercises were performed in 3 sets and each set lasted 30 seconds. 30 seconds of rest was given to participants between the sets. Vertical jump performance was determined by measuring flight time using the Bosco Mat. The vertical jump test was performed before, immediately after (0.min), and at the 5th, 10th, 15th, 20th minutes after the foam roller exercises. The countermovement jump test protocol was performed to determine the vertical jump performance of the participants. Statistical analyzes were carried out to compare the jump heights of the participants by using the two-way analysis of variance in repeated measurements. As a result of the statistical analysis, no significant difference was found in the effects of group, time, and group×time (p>0.05). In this study, it was concluded that 3 sets of 30-second foam roller exercises applied to different muscle groups did not affect the vertical jump performance.
Full-text available
Aralıklı oruç (AO), kalori kısıtlaması (KK), zaman kısıtlı beslenme (ZKB), Akdeniz diyeti (AD) ve ketojenik diyet (KD) sağlığı ve yaşam kalitesini iyileştirmek için ortaya konulan modern beslenme stratejilerinden bazılarıdır (Pace ve Crowe, 2016; Nijs vd., 2019; Elma vd., 2020). Bu bölümün konusu olan KD, yüksek oranda yağların (%75), orta düzeyde proteinlerin (%20) ve çok düşük oranda karbonhidratların (%5) kullanıldığı bir beslenme sürecini ifade etmektedir. Bu diyet yıllardır ders kitaplarında yer alan, % 45-65 karbonhidratların, %10-35 proteinlerin ve %20-35 yağların oluşturduğu klasik beslenme piramidinin (USDA, 2016) tersine çevrilmiş halidir. Bu diyet planında karbonhidratlar ve yağlar hem oransal olarak hem de sıralama olarak yer değiştirir. Başka bir ifadeyle vücudumuz glikoz yakım modundan, yağ yakım moduna geçer. Yağlar günlük enerji ihtiyacımızı sağlamamız için birincil kaynak olur. Zamanla adaptasyon gerçekleşir ve bu beslenme şekli sürdüğü sürece vücudumuz hem aldığımız besinlerdeki yağları hem de vücudumuzdaki depo yağları öncelikli enerji kaynağı olarak kullanmayı sürdürür.
Çocukların sağlıklı yetişebilmeleri için nasıl bir yol izlemeleri gerektiğini, yapabilecekleri antrenman modellemeleri hakkında genel bilgilere yer verilmiştir.
BACKGROUND: Dynamic stretching (DS) and ballistic stretching (BS) are similar stretching methods, but the differences between them are unclear. OBJECTIVE: To examine the immediate effects of unilateral hamstring DS and BS on straight leg raise (SLR), knee flexion range of motion (KF-ROM), and KF and knee extension maximal isokinetic peak torque (KF-MIPT and KE-MIPT) of the bilateral limbs. METHODS: Twelve healthy adult men performed four sets of 2 min each of non-stretching, DS, or BS of the right lower extremity. Bilateral SLR, KF-ROM, KF-MIPT, and KE-MIPT were measured pre- and post-intervention; a three-way (intervention × limb × time) repeated-measures analysis of variance (ANOVA) was used. RESULTS: The SLR of the stretched limb (p< 0.01) was higher with DS than that pre-intervention. SLR (p< 0.01) and KF-ROM (p< 0.05) of the stretched limb and SLR (p< 0.05) and KF-ROM (p< 0.05) of the contralateral limb were higher with BS than those pre-intervention. There was no significant main effect or interaction between KF-MIPT and KE-MIPT. CONCLUSION: DS and BS had slightly different effects on ROM, and neither affected muscle strength; thus, combining the techniques during warm-up might be helpful.
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Previous research has shown that passive muscle stretching can diminish the peak force output of subsequent maximal isometric and concentric contractions. The purpose of the present study was twofold: 1. to establish if the deleterious effect of stretching on performance also exists for a skill that relies on the rate of force production for success rather than peak force generation and 2. to determine if a similar effect exists for a movement that employs a stretch-shortening action. Ten participants performed two types of maximal vertical jump with and without prior stretching of the hip and knee extensors. Both static jumps (SJ) and countermovement jumps (CMJ) were executed from a force platform. Jump height was calculated from the velocity at takeoff determined from the force/time data. Stretching induced a significant (p<0.05) decrease in jump height for both the SJ (4.4 ± 1.3%) and CMJ (4.3 ± 1.3%). Thus, it appears that pre-performance stretching exercises might negatively impact skills that demand a high power output in addition to those that rely simply on maximizing peak force. Furthermore, it is possible that this detrimental effect is comparable for skills that take advantage of the stretch-shortening phenomenon and those that do not.
Objective: To evaluate the clinical and basic science evidence surrounding the hypothesis that stretching immediately before exercise prevents injury. Data Sources and Selection: MEDLINE was searched using MEDLINE subject headings (MeSH) and textwords for English- and French-language articles related to stretching and muscle injury. Additional references were reviewed from the bibliographies, and from citation searches on key articles. All articles related to stretching and injury or pathophysiology of muscle injury were reviewed. Clinical articles without a control group were excluded. Results: Three (all prospective) of the four clinical articles that suggested stretching was beneficial included a cointervention of warm-up. The fourth study (cross-sectional) found stretching was associated with less groin/buttock problems in cyclists, but only in women. There were five studies suggesting no difference in injury rates between stretchers and nonstretchers (3 prospective, 2 cross-sectional) and three suggesting stretching was detrimental (all cross-sectional). The review of the basic science literature suggested five reasons why stretching before exercise would not prevent injuries. First, in animals, immobilization or heating-induced increases in muscle compliance cause tissues to rupture more easily. Second, stretching before exercise should have no effect for activities in which excessive muscle length is not an issue (e.g., jogging). Third, stretching won't affect muscle compliance during eccentric activity, when most strains are believed to occur. Fourth, stretching can produce damage at the cytoskeleton level. Fifth, stretching appears to mask muscle pain in humans. Conclusion: The basic science literature supports the epidemiologic evidence that stretching before exercise does not reduce the risk of injury.
Objective: The purpose of the study was to investigate the effect of static stretching on the active stiffness and damping characteristics of the ankle joint plantar flexors. Design: The study was an experimental design. Background: Flexibility has static and active components. Little information is available regarding the effect of static stretching on the active stiffness of the muscle tendon unit. This may have relevance in relation to muscle tendon unit injury and the assessment of flexibility. Methods: Pre- and post-intervention free oscillation data representing active stiffness was obtained in 30 subjects using applied masses equivalent to 30% of the subject’s maximal voluntary contraction (MVC). The control group (n=15) rested between measurements, the experimental group performed 10×30 second static stretches for the ankle joint plantar-flexors.Results : No statistically significant differences were found for stiffness values (P=0·71 95%; CI−1503–2172) and damping values (P=0·94 95%; CI−0·0272–0·0195) between the control and stretching group. The trend was an increase in both parameters following stretching. Conclusions: The results imply that static stretching had no statistically significant effect on the active stiffness or damping characteristics of the muscle tendon unit as measured with applied masses equating to 30% maximal voluntary contraction. The low statistical power of the study should be considered in evaluating the results. Relevance: Flexibility is a construct with different components of measurement. Studies typically relate static flexibility measurements or exercises to injury with conflicting outcomes. This study suggests that static stretching may have no effect on active stiffness of the ankle plantar-flexors and that these findings may have value in the design of stretching programs and in aetiological studies pertaining to flexibility.
Thèse (M.S.) -- University of Memphis, 2000. Microfiche (négatif) du manuscrit dactylographié.
  • M Alter
Alter, M.J. Science of Flexibility (2nd ed.). Champaign, IL: Human Kinetics, 1996.
The acute effects of static stretching on alpha motorneuron excitability
  • L K Thigpen
  • R Moritani
  • R Thiebaud
  • J Hargis
Thigpen, L.K., R. Moritani, R. Thiebaud, and J. Hargis. The acute effects of static stretching on alpha motorneuron excitability. In: Biomechanics IX-A. D.A. Winter, R.W. Norman, R.P. Wells, K.C. Hayes, A.E. Patla, eds. Champaign, IL: Human Kinetics, 1985. pp. 352-355.