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Metabolic Responses To Exercise

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The effect of psychophysiologic self-regulation on running economy

Tommy Boone and Jeanne DeWeese
Professor and Chair
Department of Exercise Physiology
The College of St. Scholastica
Duluth, MN 55811

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BOONE, T. and J. DeWEESE. The effect of psychophysiologic self-regulation on running economy. JEPonline, Vol. 1, No. 1, 1998. The purpose of this study was to determine the physiological effects of eliciting the relaxation response during exercise.  Nine adult females volunteered to participate in this study. The subjects received 30 minutes of progressive muscle relaxation (PMR) instructions per session for eight sessions.  During the week following PMR, the subjects exercised for 30 minutes of continuous activity on the treadmill.  The first and third 10 minutes of exercise were control periods.  During the second 10 minutes (treatment period), the subjects elicited the relaxation response.  Oxygen consumption and related measures were determined using the Beckman Metabolic Measurement Cart.  A repeated measures ANOVA was used to analyze the data.  During the treatment period, there were significant (p<0.05) decreases in F_b, V_e, SBP, and RPP when compared to the two control periods. There were no significant (p>0.05) differences in V_t, VO₂, VCO₂, RER, and HR. This study showed that the elicitation of the relaxation response during exercise did not decrease submaximal VO₂ and, therefore, did not alter running economy.  Statistically significant changes in ventilation and blood pressure were associated with the elicitation of the relaxation response during exercise.  Regarding the latter findings, there is ample evidence that a reduction in RPP has a positive and unequivocal beneficial influence on the work of the heart during exercise.

Key Words: SELF-REGULATION, OXYGEN CONSUMPTION, VENTILATION, BLOOD 
PRESSURE, RUNNING ECONOMY

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Introduction
The purpose of psychophysiologic self-regulation is to learn conscious control of the autonomic nervous system in order to bring involuntary body responses (i.e., respiration, oxygen uptake, heart rate, and blood pressure) under voluntary control (1,2). Self-regulation of the visceral and somatic responses can be achieved with the practice of one or more biobehavioral interventions such as relaxation, autogenics, biofeedback, meditation, imagery, prayer, and music.  The result may be the learned control to reverse the negative effects of cardiovascular disease, evoke positive body-mind-spirit responses to stressors, or to enhance well-being through increased inner peace and calmness.

Regardless of the biobehavioral intervention used, the psychophysiologic effects on the cardiovascular system are consistent with decreased sympathetic nervous system activity (3,6) and decreased metabolism (3,4,7-9).  These responses highlight the influence of psychological states on physiological processes at rest (10,11).   Few studies have examined the effects of biobehavioral interventions during exercise. Benson, Dryer, and Hartley (12) reported decreased metabolism during exercise with elicitation of the relaxation response.  The subjects had a minimum of 6 months of relaxation training. Oxygen consumption (VO₂) decreased an average of 4% during the exercise period with relaxation.  Gervino and Veazey (13) extended the work of Benson and colleagues (12) and found that the elicitation of the relaxation response during exercise resulted in a significant decrease in the physiological cost (VO₂) of a given workload of submaximalrunning.  Ziegler, Klinzing, and Williamson (14) also reported a decrease in metabolism (VO₂) during a submaximal run that incorporated cognitive coping strategies and relaxation.  On the other hand, Smith, Gill, Crews, Hopewell, and Morgan (15) reported no significant physiological changes in VO₂ and heart rate (HR) when using relaxation during distance running. In agreement, Ashley, Rajab, Timmons, Smith, and Mutrie (16) found that 2 weeks of self-instruction in progressive muscular relaxation (PMR) had no significant effects on VO₂, HR, and expired ventilation (V_e) during submaximal running.  These findings are also consistent with earlier reports by Cadarette et al. (17) and Cortes, Boyd, and Boone (18).

This lack of consensus reflects the limited availability of research examining this topic and the ambiguity that exists in the literature.  If the volume of oxygen consumed at a fixed work intensity can be decreased with elicitation of the relaxation response and if the physiological variables, HR and VO₂, can be used to assess cardiorespiratory efficiency (i.e., exercise economy), then psychophysiologic self-regulation may translate into improved running performance.  Here, the improvement in economy is defined as using a lower percentage of maximal oxygen consumption (VO₂max) at a given submaximal running velocity (19,20).

The purpose of this study was to determine the physiological effects of eliciting the relaxation response during exercise. Our null hypothesis was that in healthy female subjects the learned self- regulation of the autonomic nervous system at rest would not be under voluntary control during exercise.

Methods
Subjects
Nine sedentary adult females (Mean age = 23±2 years; Mean mass = 59±2.9 kg; Men height = 164.2±0.8 cm) volunteered to participate in this study.  None of the subjects was engaged in a regular exercise program or relaxation training prior to the experiment. The subjects gave their informed consent, and were informed of the test procedures and purpose of the study.

Experimental Procedure
Relaxation Procedures. During the orientation day, the subjects were given verbal instructions and familiarization with a progressive muscle relaxation (PMR) strategy designed to elicit parasympathetic dominance.  This strategy required the subjects (under the direction of the instructor) to consciously tense and relax major muscle groups throughout the body to become more aware of subtle degrees of tension.  The subjects received 30 minutes of PMR instructions per session for eight sessions (using a Monday, Wednesday, and Friday schedule).  Heart rate, systolic blood pressure (SBP), and rate pressure product (RPP) were recorded at scheduled intervals to validate the PMR strategy.  The PMR sessions resulted in significant (p<.05) decreases in HR (74±9 to 63±8 beats/min), SBP (122±10 to 110±12 mm Hg), and RPP (90±6 to 69±8), respectively from the first PMR session to the eighth PMR session.

Familiarization. On Friday of the third week of the study (following the eighth PMR session), each subject reported to the laboratory to receive a general explanation of the testing protocol and to participate in a 10-minute simulation of the actual treadmill exercise.  At 0% grade, treadmill speed was determined for each subject to approximate 60% age-predicted maximum HR (using 220-age), and to standardize the relative intensity for all subjects.

Test Protocol.  During the week following the PMR instructions, the subjects returned to the laboratory for 30 minutes of continuous treadmill exercise.  During minutes 1-10, the subjects exercised without eliciting the relaxation response (Control I). During minutes 11-20, the subjects elicited the relaxation response (Treatment).  During minutes 21-30, the subjects continued to exercise but without eliciting the relaxation response (Control II).

Physiological Measures.  Frequency of breaths (F_b), tidal volume (V_t), expired ventilation (V_e), VO₂, carbon dioxide production (VCO₂), and respiratory exchange ratio (RER) were determined by the Beckman Metabolic Measurement Cart (MMC), which was calibrated prior to and checked after each test session with standardized reference gases. Heart rate was determined by 10-second electrocardiographic strips using a modified CM5 lead.  Only the values during the second 5 minutes of each 10-minute period were averaged and statistically compared.  Systolic blood pressure was determined indirectly during minutes 10, 20, and 30 by auscultation of the left brachial artery using a standard sphygmomanometer.  Rate pressure product (also commonly referred to as double product) was calculated from the formula: (RPP = HR x SBP x .01).

Statistical Analysis
To verify that the subjects were able to elicit the relaxation response following the eight PMR sessions, physiological data from the first and eighth sessions were statistically compared using a two-tailed paired t-test.  An analysis of variance with repeated measures was used to assess the mean difference for each variable across the three 10-minute exercise periods.  Where indicated, a Newman Kuels post hoc analysis was used to determine the significant differences among the means.  An alpha of 0.05 probability level was used for all tests of statistical significance.

Results
Means and standard deviations were computed for all physiological data (Table 1). Statistical analysis indicated significant differences (p<0.05) in the Treatment values for F_b, V_e, SBP, and RPP versus Control I and/or II. There were no significant differences (p>0.05) in V_t, VO₂, VCO₂, RER, and HR.

Table 1. Cardiorespiratory and hemodynamic responses at a fixed work intensity before (Control I), during (Treatment), and after (Control II) the subjects were told to try and elicit the relaxation response (M±SD).

  *ANOVA with repeated measures
**Newman Kuels post hoc analysis (p<0.05)

Discussion
The major finding of this study was that the elicitation of the relaxation response during submaximal treadmill exercise did not result in a significant decrease in VO₂.  The null hypothesis was supported.  The subjects were not able to improve their running economy (i.e., decrease VO₂) during the exercise period in which psychophysiologic self-regulation was practiced.  This finding disagrees with previous observations by Benson et al. (12), Ziegler et al. (14), and Gervino and Veazey (13), but is in agreement to those of others (15-18).

Although the mechanisms involved in producing a decrease or no change in VO₂ remain unclear and invite further investigation, several reasons might explain this finding.  First, there is much still unknown regarding the proposed integrated hypothalamic response that is hypothesized to be the relaxation response (3,4,21-23).   In particular, the suggestion that relaxation training and meditative practices (including most other biobehavioral interventions such as imagery, biofeedback, and music) result in a decrease in VO₂ at rest and during exercise is simply not correct.  This is evident with the preceding discussion that illustrates the equivocal results in the literature. Also, the case reports study by Benson, Malhorta, Goldman, Jacobs, and Hopkins (24) in which VO₂ increased during advanced meditation illustrate this point.  Second, there is the unanswered question regarding the subjects' difficulty in eliciting the relaxation response during exercise.  The subjects may state that they are able to elicit the relaxation response during exercise versus at rest, but there are no studies to support their claim. For some reason, this point does not appear to have been problematic in the previously mentioned studies and yet it might be the primary factor causing the lack of consensus. This question of "the specificity of the relaxation response" (i.e., if PMR is to be elicited during exercise, then it should be learned during exercise) needs further investigation.

Third, other factors such as motor unit recruitment patterns, anatomical and physiological characteristics, aerobic differences between trained and untrained subjects, the elimination of unnecessary aspects of running style, variations in training protocols, and the likelihood that VO₂ during submaximal running cannot be influenced beyond some physiologic limit need to be researched (25-28).  Fourth, there is the question of how long a psychophysiologic self-regulation intervention (such as relaxation training) should be practice before using it to improve running economy. Self-regulation interventions that facilitate elicitation of the relaxation response take time to engender a shift in values and beliefs. Thus it might be incorrectly hypothesized that psychophysiologic self-regulation per se (belief, for example, in PMR) is the agent of change rather than the time spent learning PMR.  Finally, there is the role of the placebo response. If the researchers and/or subjects are enthusiastic proponents of psychophysiologic self-regulation (versus being skeptics), then the results are likely to support their belief than if they did not believe in the effectiveness of the intervention (29). 

Although it is evident from the preceding discussion that mind and body are inextricably interconnected and that PMR training can produce physiologic changes at rest (e.g., decreased VO₂ and HR), the same physiologic changes during exercise are not as easily reproducible.  As mentioned earlier, VO₂ was unchanged although, in general, some authors might suggest that there was a certain trend for HR reduction (p = 0.07) during the relaxation period versus Control I. The mean HR difference did not reach significance, which is in agreement with earlier studies (12,13,17).  However, given that the subjects had learned to self-regulate specific physiologic responses at rest, and given that they were committed to eliciting the relaxation response during exercise, it is unclear why their thoughts and feelings did not produced the desired physiologic changes.  Part of the problem, again, may be that the exercise itself produces conflicting feedback.  The end result is that the subjects' thoughts, feelings, and beliefs are simply not strong enough to elicit the relaxation response. The point being, it is difficult for subjects to focus their attention on thoughts and feelings learned at rest while also experiencing the exercising condition.

Where does this leave the researcher?  It is important to point out that physiologic changes other than a decrease in VO₂ and HR occur with PMR training, and they are also manifestations of the hypothalamic response termed "relaxation."  A shift, for example, in autonomic balance to parasympathetic dominance is also characterized by significant decreases in F_b and V_e.  Theoretically, a decrease in the work of breathing at the same VO₂ would result in a reduction in the subjects' perception of effort.  The results of this study demonstrate that F_b and V_e are not fixed at a constant work intensity.  Elicitation of the relaxation response during minutes 11-20 resulted in a significant decrease in F_b and V_e of 10% and 4%, respectively.  Following the relaxation period (minutes 21-30), F_b increased by 7% while V_e remained unchanged.  These findings are consistent with the studies by Cadarette et al. (17) and Gervino et al. (13).  As such, the subjects were able to exercise at the same VO₂ throughout the three exercise periods while breathing a reduced volume of air by 4% during the elicitation of the relaxation response.  The importance of this finding is underscored by the 10% reduction in F_b, which set the stage for increased ventilatory efficiency (30).

An equally important finding is that the relaxation response during steady-state exercise produced a significant 6% decrease in SBP (from 132 to 124 mm Hg) when compared with Control I without relaxation.  Interestingly, when the subjects stopped the practice of the relaxation response and continued to exercise during Control II (again, without relaxation), the steady-state exercise was associated with a significant 6% increase in SBP.  Therefore, the elicitation of the relaxation response per se caused the subjects' SBP to decrease during exercise.  While the mechanism remains to be defined, relaxation during exercise produced a psychophysiologic state of self-regulation distinct from that found during exercise alone (Control I and II).  This finding is in agreement with the results reported by Gervino et al. (13).

The decrease in SBP suggests an improved efficiency of the central circulatory system as evident by the significant decrease in RPP, which is an established correlate of cardiac work and myocardial oxygen demand (31).  This finding is particularly important given that exercise HR did not decrease during the elicitation of the relaxation response, and that it appears to contradict the notion that PMR training results in a parasympathetic response.  Clearly, in the present study, the SBP response was the primary parasympathetic measure and, as a component of the RPP calculation, the primary method by which the work of the heart was reduced at the fixed work load which illuminates an important point.  That is, perhaps, the criterion measure for improvement in running economy should be the SBP response during the elicitation of relaxation while exercising and not the VO₂ response.  Unfortunately, too few researchers have evaluated SBP with the same interest as VO₂, and too few have looked to other physiologic measures as indices linked to running performance.

Another physiologic measure that may support the view that PMR is useful in eliciting the  the relaxation response during exercise is the calculation of RER (i.e., the ratio of CO₂ produced to O₂ consumed at the lungs).  Under steady-state conditions, RER is a reasonably valid measure of respiratory quotient (RQ, i.e., the ratio of CO₂ produced to O₂ consumed at the cells), and is a means to estimate energy metabolism during exercise.  Hence, the usefulness of RER is that it can serve as a guide to the nutrient mixture being catabolized for energy.  For example, when fat is used for energy, for a given ATP production, more O₂ is required to oxidize it to CO₂ and water than is required for carbohydrates (32).

An increase in utilization of free fatty acids to support energy production during submaximal exercise would theoretically result in an increase in the rate of VO₂(33); a physiologic response not indicative of enhanced running economy.  In fact, as it turns out, RER does not appear to be an important measure of running economy. Several studies (3,12) indicate that RER does not change during elicitation of the relaxation response, which is in agreement with the present study.  Gervino et al. (13) appears to be the only study reporting that elicitation of the relaxation response during exercise mediated a significant decrease in RER.  The authors questioned the biologic significance, however. In fact, if minimization of VO₂ is a crucial performance criterion for economical running pattern, a decrease in RER would not be expected.

The limitations inherent not only in this study but others like it include: (a) the reliance on the subjects' self-elicited relaxation response; (b) the effect of the subjects' psychological state [i.e., affect and mood] on running economy; (c) the relatively short duration to learn the PMR self-regulation technique; (d) the subjects' perception and/or belief in whether psychophysiologic self-regulation can influence the physiologic response during exercise; and (e) the degree to which the learned elicitation of the relaxation response at rest can be elicited equally as effective during exercise.

Conclusions
Given the fact that no change in VO₂ occurred during the exercise period in which the relaxation response was elicited indicates the imperturbability of the subjects' exercise metabolism and thus unchanged running economy as presently defined (34).  It is very tempting to, therefore, question VO₂ as the criterion variable for demonstrating changes in running economy.  Clearly the research efforts that have looked at the elicitation of the relaxation response during exercise have not resulted in sufficient evidence to warrant the conclusion that exercise metabolism can be systematically modified.  The results of this study reinforce rather the importance of psychophysiologic self- regulation during exercise on respiratory and myocardial variables (particularly F_b, V_e, and RPP). Regarding the latter variable, there is ample evidence that a reduction in RPP has a positive and unequivocal beneficial influence on the work of the heart.  This consideration alone may be of more practical significance than the measured VO₂ and, theoretically, may enable the performer to better tolerate the central demand associated with exercise. Based on this interpretation, not unexpectedly then, the net result is a better performance. 

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