Author Institution: Departments of Engineering and Physiology, Wright State Universit

John, Diane Ledonne

Petrofsky, Jerrold Scott

Rinehart, S.

The Ohio Journal of Science

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Copyright © 1981 Ohio Acad. Sci. 0030/0950/81/0005-0236 $2.00/0BRIEF NOTETHE INFLUENCE OF THE MENSTRUAL CYCLE ON THE BLOOD FLOWTHROUGH MUSCLE DURING ISOMETRIC EXERCISE1JERROLD SCOTT PETROFSKY, Departments of Engineering and Physiology, Wright State University,Dayton OH 45435DIANE LEDONNE, JOHN S. RINEHART, and ALEXANDER R. LIND, Department of Physiology, St.Louis University, St. Louis MO 63104OHIOJ. SCI. 81(5): 236, 1981The endurance time for fatiguing iso-metric contractions is about one-thirdlonger in women than men when contrac-tions are sustained at 40% of each indi-vidual's maximum strength (Petrofsky et al1975). Although the endurance in men re-mains somewhat constant from day to day,we have found that while this endurance isalso true for women taking oral contracep-tives, it is not the case for women with nor-mal menstrual cycles where there was asinusoidal variation in endurance through-out the cycle. The longest endurance occurs7 to 10 days after the onset of bleeding (Pet-rofsky et al 1975). Some of this variation inendurance was considered to be due to fluc-tuations in the deep muscle temperature ofthe forearms of these subjects, but a largeproportion of the variation remained un-explained. Two principal factors having animportant influence on isometric enduranceare muscle temperature (Clarke et all958)and the blood flow through the muscle dur-ing contractions (Barcroft and Millen1939). It has been shown that muscle tem-perature alone cannot account for this largevariation in endurance (Petrofsky et al1975). The purpose of this investigationwas to determine whether or not there is achange in muscle blood flow throughoutthe menstrual cycle that could account forthe change in endurance.The subjects in this study were 4 femalevolunteers. Two subjects were taking theoral contraceptive, OVULIN 21. We mea-^anuscript received 22 May 1980 and in revisedform 9 October 1980 (#80-25).sured isometric strength and endurance ona handgrip dynamometer and assessed themaximal voluntary contraction (MVC) asthe strongest of 2 brief (< 3 sec) maximalefforts. Three minutes were allowed be-tween contractions. In each experiment, 30min following the assessment of isometricstrength a tension of 40% MVC was held tofatigue (endurance time.Subjects' blood pressures were measuredby auscultation of the inactive arm before,as often as possible during, and 30 sec and60 sec after the contractions. Their heartrate was measured from a continuous re-cording of the ECG at rest and throughoutthe duration of the 40% MVC contraction.The blood flow through the forearm wasmeasured by venous occlusion plethysmog-raphy, using a mercury-in-rubber straingauge dynamometer. One minute prior toany flow measurements, a wrist cuff was in-flated to 300 mmHg to occlude the circula-tion to the hand. The blood flow was mea-sured 5 times/min at rest, during theisometric contractions, and at various inter-vals in the post exercise recovery period.The statistical analysis of the data involvedcalculation of means and standard devia-tions and related T-tests; the level for sig-nificance was P < 0.05.All subjects were trained in the experi-mental procedures over a 6 week period(Petrofsky et al 1975). Following thisperiod in each experiment, isometricstrength was determined as described aboveand 30 min later the duration of 40% MVCcontraction was measured. Blood pressure236OhioJ. Sci. MUSCLE BLOOD FLOW 237and heart rate were measured for 2 min be-fore, during and at 30 sec and 60 sec afterthe contractions and blood flow 2 min be-fore, during and from 2 to 5 min, 7 to 10min and 12 to 15 min following the con-tractions. Each experiment was conductedon Monday, Wednesday and Friday of suc-cessive weeks for 2 complete menstrual cy-cles.No statistical difference was evident ineither the strength or the endurance of the 2women taking oral contraceptives duringthe first and second halves of theirmenstrual cycles (table 1). In contrast, forthe 2 subjects with normal menstrual cy-cles, endurance during the first half of themenstrual cycle was significantly longerthan the endurance during the second halfof the menstrual cycle.Prior to the contraction, the average rest-ing forearm blood flow was the same irres-pective of the day of the menstrual cycle forthe 2 women taking oral contraceptives(table 1). During the contraction, thesesubjects showed an almost linear rise in theblood flow with time as the contractionscontinued. The peak blood flow at the endof the contractions, however, showed nosignificant difference between the first andlast halves of the menstrual cycle. Follow-ing the contractions, the blood flow reco-vered to the resting level with 12 min afterthe end of the exercise. A polynomial evalu-ation was made of the blood flows duringrecovery from each experiment to estimatethe magnitude of the total blood flow debtincurred during the recovery followingisometric exercise (area under the flow curveTABLEless resting flow). No significant differenceexisted in the average blood flow debt(blood flow debt/12 min recovery period)between the first and last halves of themenstrual cycle for the 2 women taking oralcontraceptives.In contrast, the menstrual cycle had apronounced influence on the resting, exer-cising, and recovery blood flows in the 2subjects not taking oral contraceptives. Thepre-exercise forearm blood flows measuredfor the first halves of the mentrual cycle av-eraged 1.3 and 3.0 ml/100 ml/min respec-tively. Although the highest restingforearm blood flows were found when thesubjects were in the last halves of theirmenstrual cycles, the average blood flowsduring the fatiguing contractions were sig-nificantly (P < 0.05) higher in the firsthalves of their menstrual cycles, the averagepeak exercising blood flows averaging 25.3ml/100 ml/min and 21.2 ml/100 ml/minfor the pre and post-ovulatory phases, re-spectively. The hyperaemia following exer-cise was complete within 12 min post exer-cise irrespective of the phase of themenstrual cycle; however, the averageblood debt incurred by the exercise wasgreater in the second half of the menstrualcycle (averaging 7.3 ml/100 ml/min and10.1 ml/100 ml/min); the difference wasstatistically significant (P < 0.01). No sig-nificant difference occurred between theheart rates and blood pressures recorded inthe first and last half of the menstrual cyclefor any of the subjects.As reported previously, we found amarked increase in endurance for isometric1Blood Flow and Endurance. *Strength (Kg)Endurance (sec)Blood Flow Rest(ml/lOOgm/min)Blood Flow at End Exercise(ml/100/gm/min)Blood Flow in Recovery(ml/lOOgm/min)No ContraceptivesOvulatory32.5± 2.5168 ±171.3± 1.125.3± 1.87.3± 1.0Luteal31.8± 2.7145 ±153.0± 1.421.2± 2.110.1± 1.1ContraceptivesOvulatory33.1±2.9110 ±72.1±0.824.1± 1.38.5±1.1Luteal33.6±2.3105 ±62.2±1.024.2±1.28.6±1.2*A11 data shown represent the mean ± the S.D.238 J. F. PETROFSKY, ET AL Vol. 81exercise in the pre-ovulatory phase of themenstrual cycle (Petrofsky et al 1976).Since isometric endurance is reduced whenthe temperature of the exercising muscle isincreased toward or above the core tempera-ture (Clarke et al 1958), it is not surprisingthat the post-ovulatory increase in coretemperature and the associated increase inforearm deep muscle temperature result in alower endurance for isometric exercise.Even when muscle temperature isstabilized, we found the endurance forisometric exercise still varies during themenstrual cycle.Although the effects of progesterone onperipheral blood flow are questionable,there is a marked influence of estrogen onthe blood flow through the hand and fore-arm and especially on venous tone (Nuway-hid et al 1975). Under the influence of es-trogen, the normal blood flow response toknown vasodilators may be reduced or re-versed (Lloyd and Pickford 1962). It is pos-sible, then, that the blood flow response toexercise might be reduced due to the actionof estrogen during the luteal phase of themenstrual cycle and cause the endurance forisometric exercise to be lower. A curiousfinding of our results was that the bloodflow recorded prior to and during thehyperaemia following the exercise was re-duced during the pre-ovulatory phase andenhanced during the luteal phase of themenstrual cycle. The mechanism of this re-sponse, like that during exercise, remainsvague and requires further investigation.Acknowledgments. This work was supported byAF Grant No. AFOSR-76-3084 and by the Air ForceAerospace Medical Research Lab, Dayton, Ohio,Contract No. F33615-78-C-O5O1.LITERATURE CITEDBarcroft, H. and J. L. E. Millen 1939 Blood flowthrough muscle during sustained contraction. J.Physiol. 97: 17-24.Clarke, R. S. J., R. F. Hellon and A. R. Lind 1958The duration of sustained contractions of thehuman forearm at different muscle temperatures.J. Physiol. 143: 454-463.Lloyd, S. and M. Pickford 1962 The effect of oestro-gens and sympathetic denervation on the responseto oxytocin of the blood vessels in the hind limb ofthe dog. J. Physiol. 163: 362-371.Nuwayhid, B., C. Bunkman, J. Woods, H. Mar-tinek, and N. Assali 1975 Effects of estrogens onsystemic and regional circulations in normal renalhypertensive sheep. Amer. J. Obstet. Gynocol.123:495-504.Petrofsky, J. S., R. L. Burse and A. R. Lind 1975Comparison of physiological responses of womenand men to isometric exercise. J. Appl. Physiol.38: 863-868., D. M. LeDonne, J. S. Rinehart, and A. R.Lind 1976 Isometric Strength and Endurance dur-ing the Menstrual Cycle. European J. Appl. Phys-iol. 35: 1-10.

Brief Note: The Influence of the Menstrual Cycle on the Blood Flow Through Muscle During Isometric Exercise

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Brief Note: The Influence of the Menstrual Cycle on the Blood Flow Through Muscle During Isometric Exercise

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