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117
Journal of Exercise Physiology
online
February 2013
Volume 16 Number 1
Editor-in-Chief
Tommy Boone, PhD, MBA
Review Board
Todd Astorino, PhD
Julien Baker, PhD
Steve Brock, PhD
Lance Dalleck, PhD
Eric Goulet, PhD
Robert Gotshall, PhD
Alexander Hutchison, PhD
M. Knight-Maloney, PhD
Len Kravitz, PhD
James Laskin, PhD
Yit Aun Lim, PhD
Lonnie Lowery, PhD
Derek Marks, PhD
Cristine Mermier, PhD
Robert Robergs, PhD
Chantal Vella, PhD
Dale Wagner, PhD
Frank Wyatt, PhD
Ben Zhou, PhD
Official Research Journal
of the American Society of
Exercise Physiologists
ISSN 1097-9751
Official Research Journal of
the American Society of
Exercise Physiologists
ISSN 1097-9751
JEPonline
Effects of Proprioceptive Neuromuscular Facilitation
Stretching and Static Stretching on Cardiovascular
Responses
Gabriel Costa e Silva1, Fabrízio Di Masi2, Adriana Paixão1, Cláudio
Melibeu Bentes1, Marcos de Sá1, Humberto Miranda1, Roberto
Simão1, Jefferson Novaes1
1Rio de Janeiro Federal University, Physical Education Post
Graduation Program, Rio de Janeiro, RJ – BRAZIL 2 Rio de Janeiro
State University, Laboratory of Human Motricity Biosciences, Rio de
Janeiro, RJ – BRAZIL
ABSTRACT
Costa e Silva G, Di Masi F, Paixão A, Bentes CM, Sá M, Miranda
H, Simão R, Novaes J. Effects of Proprioceptive Neuromuscular
Facilitation Stretching and Static Stretching on Cardiovascular
Responses. JEPonline. 2013;16(1):117-125. This study compared the
acute effects of static stretching (SS) and neuromuscular
proprioceptive facilitation (PNF) stretching on heart rate (HR), systolic
blood pressure (SBP), diastolic blood pressure (DBP), and oxygen
saturation (SpO2) in female athletes. Twelve subjects were randomly
divided into 3 groups (2 experimental groups (SS and FNP) and 1
control group (CS)). The groups performed stretching activities as
follows: SS (2 sets, 30 sec each for the pectoral and biceps muscles
with a 15 sec rest interval between sets); PNF (2 sets, 30 sec each for
the pectoral and biceps muscles with 6 sec of isometric contraction
and a 15 sec rest interval between sets); and CS (rest). Ten min
before and after the experimental and control activities, the subjects
had their HR, SBP, DBP, and SpO2 values measured. The results did
not demonstrate significant differences in HR, SBP, and DBP
(P>0.05) within or between the groups. However, the SpO2 values
(before vs. after exercising) were significantly (P<0.001) lower
following stretching in the SS and PNF groups but not in the CS
group. Thus, although SS exercises and PNF did not alter the HR and
pressure responses, they may induce acute deleterious effects for
upper limb development by decreasing the oxygen supply to the
muscles.
Keywords: Oxygenation, Blood Pressure and Stretching Exercises.
118
INTRODUCTION
According to the American College of Sports Medicine (1), flexibility is an important component of
good physical fitness and health. Therefore, many coaches and researchers suggest that muscle
stretching exercises should be an important component of physical activity programs (27). Recent
studies have demonstrated that stretching prior to physical activity leads to intense muscle
contraction and may affect muscle development (8,27) and yet, muscle stretching is still usually
performed prior to physical activity (8,14,16,31).
Several studies have suggested that stretching can reduce strength, power, and agility in sports
performance (2,23,29). Neural and structural modifications might also occur because of muscle strain
induced by stretching (13,20,27). Along these lines, Farinatti et al. (10) suggested that stretching
exercises performed at low flexibility levels can affect the autonomic nervous system of subjects,
leading to increased sympathetic activation.
Few studies have comprehensively examined the autonomic responses to stretching. However,
McCully (22) suggested that because of the structural changes that are caused by stretching (20), the
oxidative capacity and oxygen supply of muscles may be impaired. Thus, both static muscular
stretching exercises (11,12) and proprioceptive neuromuscular facilitation (PNF) (7,17) can potentially
reduce the size of blood vessels, leading to increased intravascular pressure. Studies such as those
by Poole et al. (25) and Otsuki et al. (24) have suggested that static stretching (SS) might decrease
blood flow. In support of this, McCuly (22) verified that SS can decrease oxygen saturation in the
quadriceps and gastrocnemius muscles.
However, no recent studies have compared the effects of different stretching methods (e.g., SS and
PNF) on heart rate (HR), systolic arterial pressure (SBP), diastolic arterial pressure (DBP), and
muscle oxygen saturation (SpO2). There also has been a lack of research involving these variables
with trained subjects. Because flexibility skills are more important in some sports (e.g., swimming and
gymnastics) than in others, the purpose of the present study was to compare the acute effects of SS
and PNF methods on the HR, SBP, DBP, and SpO2 of female swimmers and synchronized
swimmers.
METHODS
Subjects
The sample group comprised 12 normotensive female swimmers. All the subjects had previous
experience in flexibility training. They were apparently healthy and had been practitioners of the sport
for at least 5 yrs. After being provided with oral and written explanations of the procedures involved
in the study according to the Code of Ethics of the World Medical Association (Declaration of
Helsinki), all of the selected subjects signed written consent forms.
The following exclusion criteria were used: (a) ingestion of substances containing alcohol and/or
caffeine within 24 hrs of testing; (b) using nail polish; (c) a current injury or any other physical
limitation to flexibility; (d) an injury history in the upper limbs; (e) hyper- or hypomobility; (f) smoking;
and (g) physical inactivity.
119
Table 1. Participant Descriptive Data.
Variables Means ± (SD) CV (%)
Age (yrs) 17.8 ± (4.21) 7.58
Weigth (kg) 57.2 ± (2.24) 3.34
Height (cm) 165.5 ± (1.34) 2.76
BMI 19.7 ± (3.74) 3.94
HR (beats·min
-
1
) 77.9 ± (11.2) 2.14
SBP (mmHg) 122.1 ± (9.33) 5.57
DBP (mmHg) 83.3 ± (8.99) 4.49
OS (SpO
2
) 98.5 ± (2.3) 6.87
SD, standard deviation; CV, coefficient of variance; BMI, body mass index; SBP, systolic blood pressure; DBP,
diastolic blood pressure; HR, heart rate; SO, oxygen saturation; SpO2, partial oxygen pressure.
Procedures
Data collection occurred during four non-consecutive visits, each of which was scheduled at the same
time of day. On the first visit, the subjects underwent initial evaluations of their medical histories and
anthropometric measurements (i.e., total body mass, height, and body mass index (BMI)). After 10-
min of rest, the subjects’ HR, SBP, DBP, and SpO2 values were measured and, then, they underwent
tests to determine their familiarity with stretching exercises.
On the second visit, the subjects were divided into three groups using a balanced randomization input
method: two experimental stretching groups (SS and PNF) and one control group (CG).
Subsequently, the subjects in the SS group rested for 10-min and had their HR, SBP, DBP, and SpO2
levels measured twice. The mean value of the two measurements was taken for each subject. Then,
they were submitted to 2, 30-sec sets of SS of the pectoral and biceps muscles (horizontal flexion of
their shoulders, forming 90° angles with their trunks), with the range of motion to the point of
discomfort (1) and a 15-sec rest interval between the sets. Immediately after the stretching exercises,
their HR, SBP, DBP, and SpO2 values were measured twice (as before). To maintain the ecological
validity of the results, the measurements were conducted within 30 sec after stretching.
On the second visit, the subjects in the PNF group rested for 10-min before having their HR, SBP,
DBP, and SpO2 measured twice (as described above). Then, they performed 2 sets of PNF stretching
for the pectoral and biceps muscles, with 6 sec of isometric contraction followed by 24 sec of
sustained stretching (1). Each subject was allowed a 15-sec rest interval between sets. Immediately
after the stretching exercises, the HR, SBP, DBP, and SpO2 values were measured twice (as before).
To maintain the ecological validity of the results, the measurements were conducted within 30 sec
after stretching. The CS group rested for 10-min and then had their HR, SBP, DBP, and SpO2 values
measured twice (as described above). After 10-min of rest, they had the same variables measured
again.
On the 3rd and 4th visits, the experimental and control group protocols were performed in reverse.
Subjects randomly performed the SS experimental protocol, the PNF experimental protocol or the CS
at the end of the experimental procedures. The subjects reported pain ratings of 5 on a scale of 0–10
as a result of the maximum tolerated stretch, as described previously (22). During the stretching
120
exercises, the subjects were instructed to maintain normal breathing without using the Valsalva
maneuver. To determine oxygen saturation values, a wrist oximeter (Ohmeda 3740, USA) was used.
Has previously reported (21) that the partial oxygen pressure values obtained by this method are
significantly correlated (r=0.98) with the percentage of partial oxygen pressure (SpO2) and
oxyhemoglobin (HbO2) (P<0.0001). The HR was measured with a heart rate monitor (Polar 610i,
Electro Oy – Finland), and a digital sphygmomanometer (Omron HEM-742INT, USA) was used to
determine SBP and DBP.
Statistical Analyses
Shapiro-Wilk tests indicated that the descriptive data from the current sample were normally
distributed, thus validating the parametric statistical analyses. The analyses were performed using the
statistical program, SPSS, version 17.0 (SPSS Inc., USA), with a double-entry ANOVA to compare
the mean HR, SBP, DBP, and SpO2 values. Tukey’s test was used to analyze the differences within
and between the experimental protocols and control situations. Changes in the HR, SBP, DBP, and
SpO2 values after the experimental and control treatments were calculated using the effect size
method (the difference between the experimental and control mean values divided by the standard
deviation of the control) with a scale proposed by Rhea (21). In the pre-experimental and post-
experimental situations, the ICC followed by a t test was used to evaluate the reproducibility of data
between the 1st and 2nd measurements. The critical level of significance was set at P<0.05.
RESULTS
There were no significant differences (P>0.05) in HR, SBP or DBP within (before vs. after
experimental and control situations) or between the experimental protocols, as shown in Table 2.
However, the SpO2 perceptual values showed significant differences (P<0.001) within and between
the experimental protocols, as shown in Table 2.
Table 2. Means, Standard Deviations and Effect Sizes of HR, SBP, DBP and SpO2.
Static Stretching
PNF
Control
Group
Pre Post ES Pre Post ES Post
HR 88.71 ± 7.72 92.29 ± 11.69 0.46
(Small) 89.29 ± 8.46 93.14 ± 11.22 0.46
(Small) 92.71
±
8.96
103.29 ± 3.09
64.71 ± 8.24
98.00 ± 0.82
SBP 102.57 ± 5.56 108.86 ± 4.14 1.13
(Small) 107.71 ± 15.13 115.29 ± 13.03 0.50
(Small)
DBP 63.57 ± 9.54 68.71 ± 6.90 0.54
(Small) 70.00 ± 14.49 76.14 ± 13.25 0.42
(Small)
SO2 97.57 ± 0.79 90.00 ± 4.16*¥ -9.62
(Large) 97.71 ± 0.95 92.25 ± 5.38*#¥ -5.71
(Large)
PNF, proprioceptive neuromuscular facilitation; Pre, pre-experimental; Post, post-experimental; ES, effect size; HR,
heart rate; SBP, systolic blood pressure; DBP, diastolic blood pressure; SO2, oxygen saturation. *Significant
difference between the pre vs. post exercise situations (P<0.001). #Significant difference between groups static
stretching vs. PNF (P<0.001). ¥Significant difference between the experimental group (static Stretching or PNF) vs.
the control group (P<0.001).
121
All of the pre- and post-test variables (HR, SBP, DBP, and SpO2) showed excellent reproducibility
between the two different measurement time points, with indices between 0.90 and 0.99.
DISCUSSION
The aim of this study was to investigate and compare the acute effects of static and PNF stretching
on HR, BP, and oxygen saturation (SpO2) in female athletes participating in water sports. The results
indicated that SS and PNF did not significantly alter the values of HR, SBP, and DBP but significantly
decreased the values of SpO2. Heart rate and BP were not significant affected by either stretching
protocol. However, because of the biomechanical properties of the blood vessels, stretching may
result in a decrease in blood vessel diameter (25). Thus, the significant increase in oxygen
desaturation observed after stretching is likely a consequence of the resulting blood occlusion (22).
Few studies have examined the effects of stretching on the variables measured in the present study.
However, prior work has suggested that the activation of type III fibers and metaboreceptors may
inhibit the parasympathetic branch of the autonomic nervous system and chemoreflex stimulation,
thereby contributing to an increase in human HR (4,5,19). Farinatti et al. (10) have observed heart
rate variability (HRV) before, during, and after muscle stretching exercises in subjects with low
flexibility levels. Ten young men participated in a session involving tree stretching exercises for the
trunk muscles and hamstrings (3 sets, 30 sec, the maximum range of motion) and had their HR and
HRV measured. Heart rate and HRV values were monitored for 30 min after the session was
complete.
The results showed that sympathetic activity increased during the SS exercises and exhibited a slow
decrease by the end of it. The present study did not find evidence of increased HR immediately after
SS and PNF for the pectoral and biceps muscles. In addition, the magnitude of the changes in HR
that were observed was small in both of the experimental protocols (Table 2). Therefore, we
speculate that the short duration of the stretching period (2 x 30 sec) was insufficient to trigger an
acute increase in participation of the sympathetic branch from the autonomic nervous system in
female swimmers.
Farinatti et al. (11) reported that performing 4 sets of SS to the maximum point of discomfort (with 30-
sec intervals) is sufficient to significantly increase SBP in healthy male non-athletes. Such responses
may have been influenced by a contractile mechanism generated by the muscle spindles (9). Indeed,
it is possible that the muscular tension induced by stretching may have stimulated muscle and tendon
mechanoreceptors (18). Thus, the action of the muscle spindles associated with stretching to the full
range of motion could possibly result in the occlusion of blood vessels and increased SBP (12).
However, from a statistical viewpoint, such responses were not confirmed in this study. Perhaps this
result occurred because of the lower volume of training results that were used for our stretching
protocols, as recommended by ACSM (1). Our results indicate that two sets (30 sec) of SS and PNF
stretching are not sufficient to induce statistically significant increases in the HR and BP of female
athletes who participate in water sports.
Despite the slight elevation in the mean values of SBP and DBP observed after stretching, the
present results (Table 2) did not reveal any significant increases in pressure after stretching. In this
regard, the blood pressure variables and the measurement techniques employed were not particularly
sensitive to the interventions (stretching techniques). Wang et al. (30) suggested that water activity
promotes good flexibility. Thus, we speculate that these stretching protocols (SS and PNF), which do
not involve prolonged periods of muscle stretching (2 sets of 30 sec), are not sufficient to enhance the
122
levels of flexibility in female swimmers and synchronized swimmers, who already exhibit good
flexibility, and thus do not significantly alter their SBP or DBP values.
Gültekin et al. (17) submitted 32 university men to a PNF exercise session for their dominant upper
limbs. The HR, SBP and DBP and the double product (DP) and serum lactate concentration were
measured immediately before and after the session and again every minute for the first 5 minutes
following the end of the session. The authors observed a significant increase in all the variable
values. Thus, the PNF stretching method, which involves the actions of multiple different muscles,
seems to overload the cardiovascular system. However, Cornelius et al. (7) submitted 60
normotensive subjects to 3 different PNF stretching protocols without breathing controls. The
protocols differed according to whether the first protocol involved maximal isometric contraction; in
the other protocols, the subjects were instructed to perform only submaximal isometric contractions.
No significant changes in DBP were observed after performing PNF stretching; however, the authors
observed a significant increase in SBP. According to Farinatti et al. (11), breathing can significantly
influence the acute blood pressure responses to muscle stretching. Therefore, in addition to the
different samples in the studies of Cornelius et al. (7) and Gültekin et al. (17), the volunteers may
have performed the Valsalva maneuver, thus explaining the acute increase in SBP.
A study by Sharman et al. (28) suggested that the PNF method may be more effective than SS in
increasing range of motion. In this sense, autogenic inhibition and reciprocal inhibition appear to be
justifiable explanations of the increased efficiency of PNF (4). However, although the PNF method
does generate a greater range of motion, the current study showed that the SpO2 responses to SS
were significantly lower than the post-stretch responses to PNF. It is speculated, therefore, that the
PNF stretching method leads to an increased mobilization in the bloodstream because of the
associated muscle contractions (6), which most likely result in the increased production of nitric oxide,
a known vasodilator (3).
McCully (22) analyzed oxygen saturation using the near infrared spectroscopy in 14 apparently
healthy and moderately active subjects. After ten minutes of SS of the gastrocnemius, quadriceps
and hamstrings muscles, with muscle stretching to the point of pain (5 in a scale of 0-10), the results
showed that SS significantly reduced the muscular oxygen saturation levels in the quadriceps and
hamstrings muscles. The results from the present study, in addition to corroborating the results from
McCully (22), suggest that SS is able to reduce muscular oxygen saturation and that stretching for
prolonged durations can generate such a response. Therefore, two sets of stretching (each 30 sec in
duration) for the pectoral muscles seem to decrease the muscle’s demand for oxygen. However, the
magnitude of the change in SpO2 was large in both of the experimental protocols.
One limitation of the current study was that the post-test measurements were only performed
immediately after the stretching protocols, although prior studies had measured these values with
more extensive evaluations that were measured 30 min after stretching (10) or 5 min after stretching
(17). However, considering that professional and recreational athletes use stretching exercises before
their activities for a matter of seconds (e.g., we have observed competitive swimmers stretching on
the starting block), our study focused on the immediate physiological responses to stretching, which
are of great scientific importance. Another likely limitation is that the force applied during isometric
contractions in the PNF stretching protocol was not measured. In addition, variables such as levels of
endothelium-dependent vasodilators, autonomic nerve activity, cardiac output, control of hormone
levels, sleep time and eating, can interfere with this type of analysis and become limiting or
confounding factors if not controlled for during the study.
123
CONCLUSIONS
In the population sample tested here, the SS and PNF protocols used in this study did not statistically
change the HR, SBP, and DBP values in female swimmers. However, both stretching methods
decreased the partial oxygen pressure, with SS generating responses that were significantly lower
compared to those in the PNF group.
Thus, the use of pre-exercise stretching may cause acute deleterious effects to the performance of
muscles in the upper limbs by decreasing the oxygen supply to these muscles. Further studies
involving different samples, measurement techniques, muscle groups and stretching methods are
suggested to extend these results.
Adress for Correspondence: Costa e Silva GVL. Av Carlos Chagas Filho, Rio de Janeiro Federal
University, Physical Education PostGraduation Program, Cidade Universitária. Rio de Janeiro 21941-
590, RJ – BRAZIL. Phone: +55 21 22879329 / +55 21 92932598, Email: gabriel_bill04@hotmail.com.
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