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Je ponline february2013_silva

  1. 1. 117 Journal of Exercise Physiologyonline 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 1 Rio 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.
  2. 2. 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.
  3. 3. 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 (SpO2) 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
  4. 4. 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).
  5. 5. 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
  6. 6. 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.
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