Relationship of Body Core Temperature and Warm-up to Knee Range of Motion

Transcription

1 Relationship of Body Core Temperature and Warm-up to Knee Range of Motion TERRENCE M. GILLETTE, MA, PT,' GEORGE J. HOLLAND. P~D: WILLIAM J. VINCENT, EdD,3 STEVEN F. LOY, PhD4 Journal of Orthopaedic & Sports Physical Therapy This study examined the effects of submaximal, treadmill exercise-induced body core temperature (BCT) increase on selected knee range of motion (ROM). Twenty males, years old, were tested (randomized crossover) for ROM, BCT, and heart rate (HR), followed by either Treatment 1 (20 minutes of rest) or Treatment 11 (20 minutes of submaximal running). The two treatments were subsequently followed by a two-minute passive stretch. Range of motion was assessed before and after passive stretch treatment intervention. Treatment means differed for BCT and HR (p < 0.001) but not for ROM after exercise intervention. It was concluded that 20 minutes of exercise increased BCT (>I OC) but had no effect on knee ROM. Range of motion (ROM) exercises are an integral part of an overall fitness program and are often prescribed to prevent injury, enhance performance, and decrease pain associated with movement dysfunction (1 1). An exercise warm-up of sufficient intensity and duration to effect muscle temperature has been identified as a potential activity for enhancing ROM when combined with stretching (1 0). The rationale for use of warm-up activity and stretching to improve ROM is based primarily on the work of Warren et al(13, 14) and Lehmann et al (7). Their research indicated that variations in tissue temperature, mechanical load, and stretch force duration could alter biomechanical characteristics of collagen, i.e., enhance of plastic deformation. Sapega et al (lo), based upon an extensive research literature review (7, 13, 14), postu- ' Physical therapist. Center for Sports Mediine, California State Miversity, Northridge; Cummings and Gillette Sports and Orthopedtc RehaMlttation. Woodland Hills. CA. a Professor, Department of Kinesiology and Center for Sports Mediine, California State Unwersity. Northridge; codirector, Exercise Physiology Research Laboratory. Cai~fomia State University. Northridge. CA Professor. Department of Kinesiology, C aliia State University. Northridge, CA Assstant professor. Department of Kinesiology, and codirector, Exercise Physiology Research Laboratory. California State University. Northridae. CA /91/I 303-Ol26$03.oolo/O THE JOURNAL OF ORTHOPAEDIC AND SPORTS PHYSICAL THERAPY Copyright by The Orthopaedii and Sports Physical Therapy Sections of the American Physical Therapy Association lated an optimum therapeutic temperature range of OC for ROM enhancement. Body core temperature (BCT) and working intramuscular temperature (IMT) are directly related to the relative percentage of maximum oxygen consumption (O/0V02 max) at which an individual is working (9, 17). A linear relationship exists between IMT and BCT, with IMT increases being greater by more than.5oc (9). A 1.0-lS C increase in BCT has been shown to occur with 15 to 20 minutes of exercise at approximately 70 percent VOz max (9). Recent studies evaluating the effects of warm-up activity on ROM have produced inconsistent results (5, 15, 16). Wittorsson-Moller and associates (16) compared 15 minutes of cycle ergometer warm-up to massage, warm-up and massage, and warm-up and stretch. A significant increase in all ROM measurements was observed with the combined warm-up and stretch treatment. A greater percent increase in total ROM improvement was observed with the combined treatment of warm-up and stretch. However, no statistical comparisons were made among the various treatment group ROM changes. Hubley et al(5) compared 15 minutes of cycle ergometer work to hip stretching. The investigators found significant ROM increases with both treatments. The difference in ROM increase between treatments was not significant. Williford et al(15) in a nine-week, 1 &session study, compared five minutes of light progressive 126 GlLLETTE ET AL JOSPT 13:3 March 1991

2 jogging and stretch procedures to stretch alone. Significant increases in ankle, knee, shoulder, and trunk ROM occurred with both treatments. A significant difference in ROM improvement between treatments was observed in only two measures. Range of motion improvement at the ankle joint was significantly greater in the jog and stretch procedures compared to stretch alone. Trunk ROM improvement was significantly greater in the stretch treatment compared to the stretch and jog treatment. Several factors may have contributed to the above conflicting and inconclusive research re sults. One significant factor was the lack of standardized and controlled stretch application. In each study, a variety of self-applied (active) stretches were utilized, varying in stretch application force, intensity, and duration. Another factor was the significant variation in warm-up intensity. The prior warm-up routines did not adjust the exercise intensity variable for the individual subject's level of cardiovascular fitness. Therefore, different physiological exercise responses and subsequent temperature modifications may have occurred. Since BCT was not monitored in these studies, it is impossible to determine whether the exercise workloads utilized were sufficient to induce favorable morphologic changes in connective tissue. The purpose of the present study was to investigate the effect of warm-up on knee ROM, utilizing exercise sufficient to increase BCT to levels that would induce favorable morphologic changes in connective tissue. This study was designed to control several variables not addressed in previous research. Passive stretch application, exercise workload, and BCT were carefully controlled while measuring changes in ROM with a standardized methodology. The ROM variable was operationally defined as an angular measurement of knee flexion principally limited by changes in hamstring muscle length. It was hypothesized that exercise warmup sufficient to raise BCT 1.O-1 S C combined with passive stretch application would not significantly effect knee ROM compared to passive stretch alone. METHODS Twenty male volunteer subjects ranging from 18 to 35 years (X age = 27.9 years) signed an informed consent in accordance with university human subject research requirements. Subjects also completed an extensive medical health questionnaire based upon the 1986 guidelines of The American College of Sports Medicine (1) before participating in the study. Subjects with a history of spinal, lower extremity orthopaedic pathology, or cardiopulmonary limitations were excluded. To quantify current exercise habits, subjects also completed a standardized, physical activity lifestyle assessment questionnaire (3). Instrumentation Body core temperature was measured using a YSI model 49TA analog thermometer ( C, 0.01 "C resolution) with a YSI 401 disposable, sterile vinyl rectal probe (0.1 0 C accuracy) (Yellowsprings Instrumentation, 1725 Brannum Lane, Yellow Springs, Ohio 45387) (18). Heart rate (HR) and exercise workload were monitored using an integrated Quinton model 3000 EKG and model 65 treadmill system (Quinton Instruments Co., 2121 Terry Ave, Seattle, WA ). A platform with an adjustable horizontal component was secured to a standard therapy treatment table (Figure 1). The platform was used to stabilize the right thigh and pelvis at a 90" angle during ROM measurements and stretch procedures. A pulley system consisting of an adjustable stand, a %inch nylon traction cord, and suspended calibrated weights was used for the forced stretch application. Lower limb weight was assessed by a suspension method using a calibrated Hanson Laboratory scale model 895 (Shubuta, MS). Range of motion was measured with a Baseline circular goniometer (Yonkers, NY). For the purpose of defining the body composition characteristics of the subjects, percent body fat was estimated by subscapular, chest, and triceps skin fold measurements (6) using Lange skinfold calipers (Cam- Figure 1. Stabilization platform and pulley system. JOSPT 13:3 March 1991 RELATIONSHIP OF BCT TO KNEE ROM 127

3 bridge Scientific Inc., 5465 Mwselodge Rd., Cambridge, MD ). ROM Measurement Range of motion was assessed using a modified active knee extension method reported by Gajdosik and Lusin (4). This test measures the angle of knee flexion following active knee extension with the hip stabilized. The measured angle of knee flexion presumably represents hamstring tightness. The original investigators reported a testlretest Pearson correlation coefficient of r =.99 for this method. Subjects were positioned supine and secured to the stabilization platform with Velcro straps. The lateral malleolus, greater trochanter, and a midline position on the lateral knee joint were identified and ink-marked for anatomical reference. Subjects were instructed to slowly extend their right leg to a position in which the lower leg was observed to slightly oscillate between knee flexion and extension. The goniometer was then placed in line with the anatomical landmarks. The ROM was measured three times, with subjects relaxing the right leg one to two seconds between trials. An average of the three ROM measurements was used for statistical treatment. The senior author conducted all ROM measurements, and no attempt was made to control for examiner bias. Subjects were oriented to all testing procedures before test administration. Pretreatment measurements of height, body weight, and skinfold fat thickness were conducted before testing. Stabilizing platform and pulley system height were also determined and recorded. Subjects were positioned supine on the treatment table, and the thigh stabilization platform was adjusted to position the hip at a 90" angle, with the horizontal component of the platform four inches distal to the knee joint (Figure 1). The thigh and pelvis were secured to the table and platform using three, four-inch Velcro straps. Stretch Procedures Lower limb weight was measured to assist in standardizing the passive stretch application. This was accomplished by passively elevating the right lower leg to a 90" angle and suspending the ankle from a laboratory scale. The procedure was repeated three times, and an average limb weight value determined. Standardized stretch force was determined by adding two kilograms (kg) to the mean of the three limb weight measurements. To further standardize stretch force application, the pulley stand height was adjusted to provide a 90' angle of pull between the tibia and pulley system cord. This was the first study to utilize this technique to carefully standardize both the angle of pull and the magnitude of passive stretch force. Subjects were then randomly assigned to start treatment I or II and were notified of testing dates. Subjects were monitored with electrocardiogram (EKG) leads 11, V2, and V5 to detect potential deleterious cardiac response to rectal probe placement or the combined physiologic stress of treadmill exercise. The disposable rectal probe was self-inserted to a depth of cm and secured with surgical tape. Subjects were positioned supine for 10 minutes, and heart rate was monitored every 30 seconds. Research Design The research design is outlined in Table 1. Treatment I consisted of pretest measurements followed by a 20-minute supine rest period. Midtest ROM, HR, and BCT measurements were conducted while subjects remained secured to the stabilizing platform. The footlankle strap was attached to the subject and connected to the pulley system. The stretch force weight (2 kg + lower limb weight) was suspended from the pulley system. The right lower extremity was extended, and subjects were instructed to relax during the twominute passive stretch period. The passive stretch period was immediateiy followed by posttest ROM, HR, and BCT measurements. Posttest ROM measurements were repeated to determine investigator testlretest reliability. Subjects were instructed not to engage in physical activity or hamstring stretching during the 48 hours between treatments. TABLE 1 Research design Treatment I Treatment 11 Pre Heart rate Same Range of motion Same Core tempera- Same ture 20 minutes 20 minutes supine rest treadmill exercise Mid Heart rate Same Range of motion Same Core tempera- Same ture 2 minutes 2 minutes forced stretch forced stretch Post Heart rate Same Range of motion Same Core tempera- Same ture 128 GlLLETTE ET AL JOSPT 13:3 March 1991

4 Treatment II consisted of pretest measurements of HR, ROM, and BCT (Table 1) followed by completion of a 20-minute treadmill run at zero percent grade. Starting at 5.0 miles per hour (mph), treadmill speed was increased by.5 mph every 30 seconds until an exercise heart rate 65 to 75 percent of age-predicted maximum heart rate range was achieved (1, 2). Body core temperature response was monitored every minute. Treadmill speed was further increased after attaining the desired heart rate response to insure that the critical BCT threshold of 1.0 to 1.5OC above resting BCT was achieved. Heart rate and BCT were recorded the last 10 seconds of each minute of treadmill exercise. Heart rate recorded at the end of treadmill exercise was considered to be the treatment II midtest HR value. Subjects moved immediately from the treadmill to the treatment table and were secured to the stabilizing platform. Midtest ROM and BCT measurements were recorded. The standardized, two-minute passive stretch was conducted, followed by posttest ROM, HR, and BCT measurements. At this point, testing was completed and subjects were instructed not to engage in physical activity or stretching before the next treatment session in 48 hours. STATISTICAL PROCEDURES A repeated measures, two-way multiple analysis of variance (MANOVA) was used to compare within treatment and between treatment effects on ROM, HR, and BCT. Tukey's post hoc test was used to contrast cell differences. The level of significance was established at p < RESULTS Descriptive data for age and anthropometric variables appear in Table 2. Based on the physical activity lifestyle assessment, subjects exercised an average of 2.7 days a week for 15 to 30 minutes at approximately 40 to 60 percent of their age-predicted maximum heart rate. This level of habitual subject physical activity was characterized as mild to active (3). Mean data for treatments I and II appear in Table 3. Results of the MANOVA are shown in Table 4. Average peak treadmill speed was 6.4 TABLE 2 Subject descriptive data (N = 20) Age (years) 28 k3.7 Percent body fat 16 k7.0 Weight (kilograms) 82 k 14.5 Height (centimeters) 182 k7.6 TABLE 3 Pre, mid, and posttest values for body core temperature, heart rate, and range of motion Treatment I Treatment Pre BCT' BCT 37.5 ko.1 HRt 67.9 f14.9 HR 67.8 k9.6 ROM$ 17.0 k9.4 ROM 16.4 k9.3 Mid BCT 37.5 k0.5 BCT 38.6 f0.4 HR 67.3 k14.2 HR k12.3 ROM 16.7 k8.9 ROM 15.2 k9.2 Post BCT 37.5 f0.5 BCT 38.7 f0.5 HR 65.7 f12.1 HR 96.8 k14.4 ROM 12.1 k7.8 ROM 9.8 k7.2 BCT, body core temperature ("C). t HR, heart rate (beats per minute). $ ROM, range of motion (degrees). TABLE 4 Comparison of heart rate, body core temperature, and range of motion by stages and treatment Variables Compared by Stage (Re, Mid. Post) MANOVA F = p < Heart rate Body core temperature Ranae of motion Variables Compared by Treatment (I versus 11) MANOVA F = p c Heart rate Body core temperature Ranae of motion Variables Compared by Interaction MANOVA F = p < lhivariate Value F Value Heart rate Body core temperature Range of motion mph (+ 1.15) during the 20-minute treatment II exercise period. The mean peak treadmill exercise intensity represented 86 percent of the subject's age-predicted maximum HR (X = bpm). Statistical results indicated a significant (p < 0.001) within group difference for pre, mid, and posttest (stage) values on all variables (HR, BCT, ROM). Significant (p < ) between treatment effects were observed in HR and BCT, but not for ROM (univariate F = 2.95, p < ) (Tables 2-4). Significance was not observed in the mean difference between treatments for ROM at any stage (pre, mid, or post). The testlretest Pearson correlation (reliability) for the posttest ROM procedure was (r =.99). This is in full agreement with Gajdosik and Lusin (4). In addition, a more sensitive measure of reli- JOSPT 13:3 March 1991 RELATIONSHIP OF BCT TO KNEE ROM 129

5 ability, the intraclass coefficient (ICC), also yielded an acceptable value (r =.997). DISCUSSION This study was designed to assess the role of exercise-induced BCT increase on knee ROM based on three premises. First, theoretical morphologic animal models show that elevations in tissue temperature alter biomechanical characteristics of collagen and periarticular connective tissue (7, 13,14). Secondly, there is a demonstrated relationship between relative percentage of exercise capacity and BCT increase (9, 17). Thirdly, recent research demonstrates positive changes in ROM brought about by "aerobic" exercise (5, 15, 16). The intent of this study was to standardize passive stretch application with regard to angle, magnitude, and duration; BCT response to the exercise workload; and ROM measurement techniques. The ROM measurement technique utilized by the investigators in this study was found to be consistent and reproducible (r =.997). This is consistent with the similar active knee extension technique used by Gajdosik and Lusin, who reported testlretest reliability of r =.99 (4). The findings of this study reinforce the role of passive stretch for improving ROM (8, 12, 15, 16). The passive stretch technique used in this investigation resulted in a significant increase in - knee ROM in both treatment groups (T~eatment I X increase = 4.6 degrees; Treatment II X increase = 5.4 degrees). Research by Warren and associates (13, 14) established the influence of increased tissue temperature on favorably altering the mechanical characteristics of connective tissue collagen. This study was the first investigation to examine the effects of exercise-induced BCT increase (at a previously defined therapeutic level) of greater than 38.0 C on modifying connective tissue morphologic characteristics (10). Consistent with previous investigations, treadmill exercise alone did not significantly improve ROM (15, 16). The midtest knee ROM difference of 1.5 degrees between the basal and exercise treatment groups was not significant. The increased ROM observed in this study with combined exercise intervention and passive stretch was not statistically different from the control (p = 0.102). The energy expenditure required to achieve the temperature increase criterion of r1.o C BCT represented 86.0 percent (f 1.6) of the subject's age-predicted maximum HR. From a practical perspective, this finding tends to negate any potential enhancement of ROM through the combined exercise and passive stretch protocol utilized in this research design. It should be noted that pretest knee ROM values reported in the present study (X = degrees) were better than values reported by Gajdosik and Lusin (X = ) on 15 younger male subjects (X = 21 f 5 years) (4). Whether or not the baseline flexibility characteristics of subjects in this study influenced the exercise and/or stretch treatment results is unclear. The study's investigators believe that 20 minutes of exercise at 86 percent of maximum heart rate would not be practical as a therapeutic regime prior to a passive or active stretching routine. Research is needed to further delineate the temperature change criterion, exercise durationintensity, and the optimum passive stretch magnitude and duration needed to enhance ROM modification. The rate at which ROM changes and the retention of ROM gains after controlled passive stretch may be factors to specifically consider when quantifying the effects of exerciseinduced BCT changes. The present study addressed potential morphologic changes in the actively exercised muscle group. An unanswered postulate is whether such morphologic adaptations are limited to the specific exercising muscle or manifested throughout the nonexercising skeletal muscle of the subject. CONCLUSION The findings of this study reinforce the use of passive stretch to increase ROM. Knee ROM was significantly (p = 0.001) improved after passive stretch in both treatment groups. Twenty minutes of running, sufficient to raise BCT greater than l.o C by itself, had no effect on knee ROM. Twenty minutes of running sufficient to raise core temperature greater than 1.O C combined with passive stretch had no effect on knee ROM when compared to passive stretch alone. 0 REFERENCES 1. American College of Sports Mediine Guidelines for Exercise Testing and Prescription. Philadelphia: Lea and Febiger Astrand P. Rodahl K: Textbook of Work Phys~ology. Physiological Basis of Exerc~se. New York: McGraw-Hill Brewer C. Holland G. Vincent W. Madison R. Hoffman J, Caston A. Leake P. Danielson S. Heng M. Marin J. Reese S. Weber F. Rich G: Prelimmary analysis of a new physical activity questionnalre. Int J Sports Med 4: Gajdosik A. Lusm G: Reliability of an active knee extension test. Phys Ther , Hubley C. Kozey J. 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6 10. Sapega AA. Quendenfeld TC. Moyer RA. Butler RA: Biophysical factors in range of motion exercise. Phys Sportsmed 9: Shellock FG. Prentice WE: Waning-upand stretching for improved physical performance and prevention of sports related injuries. Sports Med 2: Toft E. Espersen GT. Kalund S. Sinkjaer, Homemann BC: Passive tension of the ankle before and after stretching. Am J Sports Med 17: Warren CG. Lehmann JF, KoManski JN: Heat and stretch procedures. An evaluat~on using rat tail tendon. Arch Phys Med Rehabil 57: Warren CG, Lehmann JF. KoManski JN: Elongation of rat tail tendon: effect of load and temperature. Arch Phys Med Rehabil Williford H. East J. Smii F. Burry L: Evaluation of warm-up for improvement in Rexibility. Am J Sports Med l4: W~ttorsson-Mdler M. Oberg B. Ekstrand J. Gillquist J: Effects of warming up, massage, and stretching on range of motlon and muscle strength in the lower extremity. Am J Sports Med 11 : Wyndham C. St+ N. VanRensburg A. Benade A. Heyns A: Relation between V02 max and body core temperature in hot hum~d air conditions. J Appl Physid 29: YSI Scientific Critical Care Patient Monitoring, pp Yellow Springs. Ohlo: Yellow Springs Instrumentation. May 1986 Journal of Orthopaedic & Sports Physical Therapy JOSPT 13:3 March 1991 RELATIONSHIP OF BCT TO KNEE ROM