The McCollough effect across the menstrual cycle.

The McCollough effect (ME) has been shown to be sensitive to cholinergic agents, being strengthened by hyoscine (antagonist) and weakened by physostigmine (agonist), and possibly to more generalized changes in CNS arousal. We therefore expected the ME to be sensitive to hormonal changes during the menstrual cycle, being strongest in the postovulatory phases when arousal is low. In two experiments we found a highly significant effect of menstrual phase for the normally cycling women, but not for oral contraceptive users: ME strength gradually increased across the cycle, reaching a premenstrual peak. These findings may be explained in terms of hormonally mediated changes in arousal across the menstrual cycle.

PIP: The hypothesis that the strength of the McCollough effect (ME) varies systematically through the menstrual cycle was investigated. 32 women, 10 of whom were using oral contraceptives (OCs), participated in the first phase of the study; another 9 women were enrolled in a second experiment. Since the initial strength of the ME is inversely related to levels of cholinergic activity, it was expected that the effect would be strongest in the first part of the menstrual cycle when rising estrogen levels reduce cholinergic activity. Alternatively, if the ME is affected inversely by central nervous system (CNS) arousal, ME strength would be greatest in the second part of the cycle when rising progesterone levels have a deactivating effect, reducing arousal. ME strength gradually increased across the cycle, reaching a premenstrual peak. Estrogen and progesterone level remained high for the early part of the premenstrual phase, then fell sharply at day 27-28. The postovulatory combination of estrogen and progesterone had a deactivating effect on the CNS, reducing arousal. OC users had reduced MEs relative to normally cycling women, except at menses. These results suggest that the variability in ME strength is attributable to hormonally mediated changes in CNS arousal across the cycle.

Oxygen consumption following exercise of moderate intensity and duration.

To study the effects of exercise intensity and duration on excess postexercise oxygen consumption (EPOC), 8 men [age = 27.6 (SD 3.8) years, VO2max = 46.1 (SD 8.5) ml min-1 kg-1] performed four randomly assigned cycle-ergometer tests (20 min at 60% VO2max, 40 min at 60% VO2max, 20 min at 70% VO2max, and 40 min at 70% VO2max). O2 uptake, heart rate and rectal temperature were measured before, during, and for 1 h following the exercise tests. Blood for plasma lactate measurements was obtained via cannulae before, and at selected times, during and following exercise. VO2 rapidly declined to preexercise levels following each of the four testing sessions, and there were no differences in EPOC between the sessions. Blood lactate and rectal temperature increased (P < 0.05) with exercise, but had returned to preexercise levels by 40 min of recovery. The results indicate that VO2 returned to resting levels within 40 min after the end of exercise, regardless of the intensity (60% and 70% VO2max) or duration (20 min and 40 min) of the exercise, in men with a moderate aerobic fitness level.

Adrenal activation and the prolactin response to exercise in eumenorrheic and amenorrheic runners.

Adrenocorticotropic hormone (ACTH), cortisol, and prolactin responses following maximal and submaximal (40 min at 80% maximal O2 consumption) running were studied in eumenorrheic (ER; n = 8, 29.0 +/- 1.5 yr) and amenorrheic (AR; n = 8, 24.5 +/- 2.0 yr) runners. ER were studied in the early follicular and midluteal phases of the menstrual cycle. Physical, training, and gynecological characteristics were similar, and cardiorespiratory and metabolic responses to the exercises were indistinguishable in the groups. ACTH, cortisol, and prolactin data from the follicular luteal phases in ER were combined for comparison to AR, because no differences were noted between the menstrual phases at rest. Similar preexercise ACTH levels and responses following exercise occurred in both groups, but preexercise cortisol levels were elevated (ER = 293.1 +/- 46.3, AR = 479.6 +/- 42.4 nmol/l) and cortisol responses blunted in AR. Adrenal sensitivity was blunted in AR compared with ER after submaximal (ER = 121.9 +/- 17.4, AR = 51.7 +/- 13.6) and maximal exercise (ER = 27.9 +/- 9.2, AR = 12.1 +/- 3.8). Preexercise prolactin levels were reduced (ER = 16.4 +/- 2.7, AR = 10 +/- 2.3 micrograms/l), and prolactin responses to maximal exercises were blunted in AR, despite high lactate levels (11.4 +/- 0.4 mmol/l). We conclude that 1) control for menstrual phase in ER is important in studies of prolactin responses following exercise but not in studies of ACTH and cortisol responses following exercise, 2) cortisol responses following submaximal and maximal exercise in AR are blunted at the adrenal level, 3) prolactin responses following submaximal and maximal exercise are also blunted in AR, and 4) prolactin responses following exercise may be mediated by adrenal activation.

Effects of menstrual phase and amenorrhea on exercise performance in runners.

There are few well controlled studies in terms of subject selection, menstrual classification, and exercise protocol that have examined both maximal and submaximal exercise responses during different phases of the menstrual cycle in eumenorrheic runners and compared these runners to amenorrheic runners. Thus, the purpose of this study was to measure selected physiological and metabolic responses to maximal and submaximal exercise during two phases of the menstrual cycle in eumenorrheic runners and amenorrheic runners. Eight eumenorrheic runners (29.0 +/- 4.2 yr) and eight amenorrheic runners (24.5 +/- 5.7 yr) matched for physical, gynecological, and training characteristics were studied. The eumenorrheic runners performed one maximal and one submaximal (40 min at 80% VO2max) treadmill run during both the early follicular (days 2-4) and midluteal (6-8 d from LH surge) phases. The amenorrheic runners performed one maximal and one submaximal (40 min at 80% VO2max) treadmill run. Cycle phases were documented by urinary luteinizing hormone and progesterone assays and by plasma estradiol and progesterone assays. No differences were observed in oxygen uptake, minute ventilation, heart rate, respiratory exchange ratio, rating of perceived exertion, time to fatigue (maximal), and plasma lactate (following the maximal and submaximal exercise tests) between the follicular and luteal phases in the eumenorrheic runners and the amenorrheic runners. We conclude that neither menstrual phase (follicular vs luteal) nor menstrual status (eumenorrheic vs amenorrheic) alters or limits exercise performance in female athletes.

Menstrual status and plasma vasopressin, renin activity, and aldosterone exercise responses.

The effects of menstrual cycle phase (early follicular vs. midluteal) and menstrual status (eumenorrhea vs. amenorrhea) on plasma arginine vasopressin (AVP), renin activity (PRA), and aldosterone (ALDO) were studied before and after 40 min of submaximal running (80% maximal O2 uptake). Eumenorrheic runners were studied in the early follicular and midluteal phases determined by urinary luteinizing hormone and progesterone and plasma estradiol and progesterone assays; amenorrheic runners were studied once. Menstrual phase was associated with no significant differences in preexercise plasma AVP or PRA, but ALDO levels were significantly higher during the midluteal phase than the early follicular phase. Plasma AVP and PRA were significantly elevated at 4 min after the 40-min run in the eumenorrheic runners during both menstrual phases and returned to preexercise levels by 40 min after exercise. Plasma ALDO responses at 4 and 40 min after exercise were higher in the midluteal phase than the early follicular phase. Menstrual status was associated with no significant differences in preexercise AVP or PRA; however, ALDO levels were significantly higher in the amenorrheic runners. After exercise, responses in the amenorrheic runners were comparable with the eumenorrheic runners during the early follicular phase. Thus, submaximal exercise elicits significant increases in plasma AVP and PRA independent of menstrual phase and status. However, plasma ALDO is significantly elevated during the midluteal phase, exercise results in a greater response during this menstrual phase, and amenorrheic runners have elevated resting levels of ALDO.

Prospective study of burn wound excision of the hands.

To examine the role of early excision and grafting in the preservation of maximal function of hands with deep dermal burns, we prospectively evaluated 164 burned hands in consecutively admitted patients (mean age, 29 years; mean burn size, 37% of body surface). All hands with burn depths of second degree, deep second degree, or third degree above the level of the tendons and joint capsules were assessed preoperatively, intraoperatively, and at discharge from the hospital. Patients were treated by excision and grafting in the first or second postburn week, by delayed grafting alone, or by allowing primary healing. Total active range of motion measurements were made on the day of discharge (mean, 64th postoperative day). Mean operative blood loss per hand was 1,270 ml. When all (alive and dead) patients undergoing early excision and grafting were examined by a binomial probability model, early surgery was shown to produce no adverse affect on survival. Excision and grafting of hands with deep dermal burns, whether early or late, offered no advantage over physical therapy and primary healing in maintaining hand function. Likewise, hands with more superficial burns responded equally to operative and nonoperative treatment. While early excision and grafting of hands with third-degree burns tended to produce poorer results than did initial nonoperative care and late grafting, the differences are just outside the range of significance. Early excision and grafting of selected third-degree injuries of the hands may be indicated in patients with small total body surface burns in order to shorten hospital stay. However, early surgical intervention in patients with massive burns should be directed toward area coverage, not toward hand excision.