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1.
David C. Poole Susan A. Ward Brian J. Whipp 《European journal of applied physiology》1990,59(6):421-429
Summary The tolerable work duration (t) for high-intensity cycling is well described as a hyperbolic function of power (W):W=(W'·t
−1)+W
a
, whereW
a
is the upper limit for sustainable power (lying between maximumW and the threshold for sustained blood [lactate] increase,Θ
lac), andW' is a constant which defines the amount of work which can be performed >W
a
. As training increases the tolerable duration of high-intensity cycling, we explored whether this reflected an alteration
ofW
a
,W' or both. Before and after a 7-week regimen of intense interval cycle-training by healthy males, we estimated (^)Θ
lac and determined maximum O2 uptake
;W
a
;W'; and the temporal profiles of pulmonary gas exchange, blood gas, acid-base and metabolic response to constant-load cycling
at and aboveW
a
. Although training increased
(24%),
(15%) andW
a
(15%),W' was unaffected. For exercise atW
a
, a steady state was attained for
, [lactate] and pH both pre- and post-training, despite blood [norepinephrine] and [epinephrine] ([NE], [E]) and rectal temperature
continuing to rise. For exercise >W
a
, there was a progressive increase in
(resulting in
at fatigue), [lactate], [NE], [E] and rectal temperature, and a progressive decrease for pH. We conclude that the increased
endurance capacity for high-intensity exercise following training reflects an increasedW asymptote of theW−t relationship with no effect on its curvature; consequently, there is no appreciable change in the amount of work which can
be performed aboveW
a
. Furthermore, regardless of training status,W
a
represents the upper power limit at which
, blood [lactate] and blood pH can eventually be stabilized. Exercise >W
a
, in contrast, is characterized by a steadily increasing
and blood [lactate], a falling blood pH and consequently, imminent fatigue.
Supported in part by a UCLA Graduate Division Doctoral Research Award 相似文献
2.
Summary Metabolic responses during a standardized, progressive, maximal work capacity test on a cycle ergometer were studied in 11 women, mean age 28 (SEM 2) years, at admission to the study, after their body iron stores were depleted by diet, phlebotomy and menstruation for about 80 days and after iron repletion by diet for about 100 days, including daily iron supplementation (0.9 mmol iron as ferrous sulfate) for the last 14 days of repletion. Iron depletion was characterized by a decline (P<0.05) in hemoglobin, ferritin and body iron balance. Iron repletion, including supplementation, increased (P<0.05) hemoglobin, ferritin and iron balance. No changes were observed in cardiovascular and ventilatory responses or peak oxygen uptake. Iron depletion was associated with a reduced (P<0.05) rate of oxygen utilization, total oxygen uptake and aerobic energy expenditure, and elevated (P<0.05) peak respiratory exchange ratio and post-exercise concentration of lactate. Reduction of body iron stores without overt anemia affects exercise metabolism by reducing total aerobic energy production and increasing glycolytic metabolism. 相似文献
3.
James E. Hansen Richard Casaburi Dan M. Cooper Karlman Wasserman 《European journal of applied physiology》1988,57(2):140-145
Summary We postulated that the commonly observed constant linear relationship between
and work rate during cycle ergometry to exhaustion is fortuitous and not due to an unchanging cost of external work. Therefore we measured
continuously in 10 healthy men during such exercise while varying the rate of work incrementation and analyzed by linear regression techniques the relationship between
and work rate (
/ wr). After excluding the first and last portions of each test we found the mean ±SD of the
/ wr in ml · min–1· W–1 to be 11.2±0.15, 10.2±0.16, and 8.8±0.15 for the 15, 30, and 60 W·min–1 tests, respectively, expressed as ml·J–1 the values were 0.187±0.0025, 0.170±0.0027 and 0.147±0.0025. The slopes of the lower halves of the 15 and 30 W·min–1 tests were 9.9±0.2 ml·min–1·W–1 similar to the values for aerobic work reported by others. However the upper halves of the 15, 30, and 60 W·min–1 tests demonstrated significant differences: 12.4±0.36 vs 10.5±0.31 vs 8.7±0.23 ml·min–1·W–1 respectively. We postulate that these systematic differences are due to two opposing influences: 1) the fraction of energy from anaerobic sources is larger in the brief 60 W·min–1 tests and 2) the increased energy requirement per W of heavy work is evident especially in the long 15 W·min–1 tests. 相似文献
4.
Immunohistochemical localization of oestrogen receptors and progesterone receptors in the human ovary throughout the menstrual cycle 总被引:7,自引:0,他引:7
Toshiko Iwai Yoshihiko Nanbu Masazumi Iwai Shunzou Taii Shingo Fujii Takahide Mori 《Virchows Archiv : an international journal of pathology》1990,417(5):369-375
Summary Immunohistochemistry was used to determine the distribution of oestrogen receptors (ER) and progesterone receptors (PR) in the human ovary during folliculogenesis. Primordial and preantral follicles did not contain ER or PR. The granulosa cells of antral follicles had ER, but negligible PR, before the LH surge. In contrast, at the time of LH surge, these cells of the dominant follicle contained PR, but not ER. On the other hand, granulosa cells of the non-dominant follicles had ER, but not PR. After ovulation, the PR persisted in the luteinized granulosa cells and in the corpus luteum during early pregnancy. The theca interna and surrounding stromal cells were ER-negative and PR-positive throughout the menstrual cycle. Thus, the results show that ER and PR are not expressed simultaneously in the granulosa cells, the thecal cells, or the stromal cells during folliculogenesis. Mechanisms controlling the expression of steroid receptors during the normal menstrual cycle and in early pregnancy are discussed. 相似文献
5.
The concept of the accumulated O2 deficit (AOD) assumes that the O2 deficit increases monotonically with increasing work rate (WR), to plateau at the maximum AOD, and is based on linear extrapolation of the relationship between measured steady-state oxygen uptake (O2) and WR for moderate exercise. However, for high WRs, the measured O2 increases above that expected from such linear extrapolation, reflecting the superimposition of a "slow component" on the fundamental O2 mono-exponential kinetics. We were therefore interested in determining the effect of the O2 slow component on the computed AOD. Ten subjects [31 (12) years] performed square-wave cycle ergometry of moderate (40%, 60%, 80% and 90%
), heavy (40%), very heavy (80%) and severe (110% O2 peak) intensities for 10–15 min, where
is the estimated lactate threshold and is the WR difference between
and O2 peak. O2 was determined breath-by-breath. Projected "steady-state" O2 values were determined from sub-
tests. The measured O2 exceeded the projected value after ~3 min for both heavy and very heavy intensity exercise. This led to the AOD actually becoming negative. Thus, for heavy exercise, while the AOD was positive [0.63 (0.41) l] at 5 min, it was negative by 10 min [–0.61 (1.05) l], and more so by 15 min [–1.70 (1.64) l]. For the very heavy WRs, the AOD was [0.42 (0.67) l] by 5 min and reached –2.68 (2.09) l at exhaustion. For severe exercise, however, the AOD at exhaustion was positive in each case: +1.69 (0.39) l. We therefore conclude that the assumptions underlying the computation of the AOD are invalid for heavy and very heavy cycle ergometry (at least). Physiological inferences, such as the "anaerobic work capacity", are therefore prone to misinterpretation. 相似文献
6.
André L. Teixeira Plínio S. Ramos Lauro C. Vianna Djalma R. Ricardo 《Psychophysiology》2015,52(11):1451-1455
Previous studies have shown that resting heart rate variability (HRV) is modified by different phases of the menstrual cycle in nonusers of oral contraceptive pills (OCP); however, the effect of OCP on autonomic control of the heart remains unclear. The purpose of this study was to investigate HRV during the low hormone (LH—not taking OCP) and during the high hormone (HH—active OCP use) phases of the menstrual cycle in young women. Seventeen healthy women (19–31 years) taking OCP for at least 6 consecutive months were enrolled in this study. Plasma estradiol and progesterone were verified at each visit. HRV was assessed by using one‐lead electrocardiography in time and frequency domains, in which participants rested in the supine position for a 20‐min period with a breathing rate of 15 cycles/min. In addition, resting heart rate, and systolic and diastolic blood pressure were obtained. Both plasma estradiol (LH: 19.8 ± 4.2 pg/mL vs. HH: 12.4 ± 1.5 pg/mL; p > .05) and progesterone (LH: 0.247 ± 0.58 ng/mL vs. HH: 0.371 ± 0.08 ng/mL; p > .05) (mean ± SE) levels were similar in both phases. No significant difference was obtained for any component of HRV, heart rate, or blood pressure between the LH and HH phases (p > .05). These results provide preliminary evidence that use of OCP does not affect HRV during the menstrual cycle in healthy women. 相似文献
7.
Carlo Capelli Guglielmo Antonutto Paola Zamparo Massimo Girardis Pietro Enrico di Prampero 《European journal of applied physiology》1993,66(3):189-195
Summary The mechanical power (Wtot, W·kg–1) developed during ten revolutions of all-out periods of cycle ergometer exercise (4–9 s) was measured every 5–6 min in six subjects from rest or from a baseline of constant aerobic exercise [50%–80% of maximal oxygen uptake (VO2max)] of 20–40 min duration. The oxygen uptake [VO2 (W·kg–1, 1 ml O2 = 20.9 J)] and venous blood lactate concentration ([la]b, mM) were also measured every 15 s and 2 min, respectively. During the first all-out period, Wtot decreased linearly with the intensity of the priming exercise (Wtot = 11.9–0.25·VO2). After the first all-out period (i greater than 5–6 min), and if the exercise intensity was less than 60% VO2max, Wtot, VO2 and [la]b remained constant until the end of the exercise. For exercise intensities greater than 60% VO2max, VO2 and [la]b showed continuous upward drifts and Wtot continued decreasing. Under these conditions, the rate of decrease of Wtot was linearly related to the rate of increase of V [(d Wtot/dt) (W·kg–1·s–1) = 5.0·10–5 –0.20·(d VO2/dt) (W·kg–1·s–1)] and this was linearly related to the rate of increase of [la]b [(d VO2/dt) (W·kg–1·s–1) = 2.310–4 + 5.910–5·(d [la]b/dt) (mM·s–1)]. These findings would suggest that the decrease of Wtot during the first all-out period was due to the decay of phosphocreatine concentration in the exercising muscles occurring at the onset of exercise and the slow drifts of VO2 (upwards) and of Wtot (downwards) during intense exercise at constant Wtot could be attributed to the continuous accumulation of lactate in the blood (and in the working muscles). 相似文献
8.
Summary The purpose of this investigation was to compare differences between one- and two-legged exercise on the lactate (LT) and ventilation (VT) threshold. On four separate occasions, eight male volunteer subjects (1-leg
=3.36 l · min–1; 2-leg
=4.27 l · min–1) performed 1- and 2-legged submaximal and maximal exercise. Submaximal threshold tests for 1- and 2-legs, began with a warm-up at 50 W and then increased every 3 minutes by 16 W and 50 W, respectively. Similar increments occurred every minute for the maximal tests. Venous blood samples were collected during the last 30 s of each work load, whereas noninvasive gas measures were calculated every 30 s. No differences in
(l · min–1) were found between 1- and 2-legs at LT or VT, but significant differences (p<0.05) were recorded at a given power output. Lactate concentration ([LA]) was different (p<0.05) between 1-and 2-legs (2.52 vs. 1.97 mmol · l–1) at LT. This suggests it is
rather than muscle mass which affects LT and VT.
for 1-leg exercise was 79% of the 2-leg value. This implies the central circulation rather than the peripheral muscle is limiting to
.Supported by NSERC A7555 相似文献
9.
Twelve females were tested at four times during the menstrual cycle with a visual detection task and a visual pattern discrimination task. Mood levels and confidence ratings were evaluated for each session. In addition to the behavioral testing, plasma samples were collected and radioimmunoassayed for estradiol, progesterone, luteinizing hormone, and follicle stimulating hormone levels. Visual detection fluctuated significantly during the menstrual cycle with impaired performance occurring at the premenstrual session. In contrast to previous reports, the impaired performance was not related to lowered confidence ratings or to mood levels. 相似文献
10.
Bangsbo J Gibala MJ Howarth KR Krustrup P 《Pflügers Archiv : European journal of physiology》2006,452(6):737-743
It was proposed that a contraction-induced increase in tricarboxylic acid cycle intermediates (TCAI) is obligatory for the increase in muscle oxygen uptake at the start of exercise. To test this hypothesis, we measured changes in muscle TCAI during the initial seconds of intense exercise and used dichloroacetate (DCA) in an attempt to alter the level of TCAI. Five men performed strenuous leg kicking exercise (64±8 W) under noninfused control (CON) and DCA-supplemented conditions; biopsies (vastus lateralis) were obtained at rest and after 5, 15, and 180 s of exercise. In CON, the total concentration of three measured TCAI (ΣTCAI: citrate, malate, and fumarate) increased (p<0.05) by 71% during the first 15 s of exercise. The ΣTCAI was lower (p<0.05) in DCA than in CON at rest [0.18±0.02 vs 0.64±0.09 mmol kg−1 dry weight (d.w.)], after 5 s (0.30±0.07 vs 0.85±0.14 mmol kg−1 d.w.), and 15 s of exercise (0.60±0.07 vs 1.09±0.16 mmol kg−1 d.w.), but not different after 3 min (3.12±0.53 vs 3.23±0.55 mmol kg−1 d.w.). Despite differences in the level of muscle TCAI, muscle phosphocreatine degradation was similar in DCA and CON during the first 15 s of exercise (17.5±3.3 vs 25.6±4.1 mmol kg−1 d.w.). Taken together with our previous observation that DCA does not alter muscle oxygen uptake during the initial phase of intense leg kicking exercise (Bangsbo et al. Am J Physiol 282:R273–R280, 2002), the present data suggest that muscle TCAI accumulate during the initial seconds of exercise; however, this increase is not essential for the contraction-induced increase in mitochondrial respiration. 相似文献
11.
Summary Six endurance-trained young men were subjected to a 4 min maximal aerobic treadmill run (100% of VO2 max), after active or passive warm-up or rest on separate days. The increase in body temperature during the active and passive warm-up was controlled, so that the temperature reached the same level, before the subject was exposed to the maximal exercise. On average the rectal temperature rose to 38.3 C (range 38.1–38.6 C). The standard work resulted in a significant higher oxygen uptake, lower lactate concentration and higher blood pH when the work was preceded by active warm-up as compared with passive or no warm-up. The difference in total oxygen uptake during the run between the active and passive warm-up procedure was 0.8 l. No significant difference in minute volume of expired air or respiratory quotient was found. It is concluded that the physiological effects of a thorough active warm-up may be of substantial benefit to athletic performance. 相似文献
12.
A. Ardévol C. Adán L. Franco P. García-Lorda F. Rubio X. Remesar J. A. Fernández-López J. Salas-Salvadó M. Alemany 《Pflügers Archiv : European journal of physiology》1998,435(4):495-502
A series of untrained, healthy, obese women (body mass index 32.5 ± 0.9 kg·m–2) were subjected to a protocol of intense exercise on a cycloergometer and compared with lean controls (body mass index 20.9 ± 0.5 kg·m–2). Physiological parameters, blood lactate, bicarbonate, plasma metabolites, oxygen consumption and CO2 production were measured. Impedance-derived extracellular water and plasma changes in lactate and bicarbonate were used to
determine changes in bicarbonate pools and lactate-displaced CO2. From these and respiratory gases, the respiratory quotient was calculated and thence overall fuel consumption. Anaerobic
energy during exercise accounted for about 1.8% of all energy consumed in the lean but only 0.7% in the obese. Obese women
fatigued at lower workloads and energy expenditure levels than did the lean, and their lactate buildup was similar when compared
on the basis of fat-free mass. The data support the postulation of fatigue being triggered by a combination of factors: stretched
cardiovascular work would be the main factor for obese women, in part limiting lactate production. For lean women, the triggering
factor for fatigue could be the loss of buffering capacity; but it is the combination of stretching cardiovascular capacity,
exhaustion of glycogen and available glucose and increase in lactate/loss of bicarbonate buffer that determines the onset
of fatigue.
Received: 10 December 1996 / Received after revision: 26 May 1997 / Accepted: 20 October 1997 相似文献
13.
Stanford KI Mickleborough TD Ray S Lindley MR Koceja DM Stager JM 《European journal of applied physiology》2006,96(6):703-710
The main aim of this study was to investigate whether there is a relationship between menstrual cycle phase and exercise-induced
bronchoconstriction (EIB) in female athletes with mild atopic asthma. Seven eumenorrheic subjects with regular 28-day menstrual
cycles were exercised to volitional exhaustion on day 5 [mid-follicular (FOL)] and day 21 [mid-luteal (LUT)] of their menstrual
cycle. Pulmonary function tests were conducted pre- and post-exercise. The maximal percentage decline in post-exercise forced
expiratory volume in 1 s (FEV1) and forced expiratory flow from 25 to 75% of forced vital capacity (FEF25–75%) was significantly greater (P<0.05) on day 21 (mid-LUT phase) (−17.35±2.32 and −26.28±6.04%, respectively), when salivary progesterone concentration was
highest, compared to day 5 (mid-FOL phase) (−12.81±3.35 and −17.23±8.20%, respectively), when salivary progesterone concentration
was lowest. The deterioration in the severity of EIB during the mid-LUT phase was accompanied by worsening asthma symptoms
and increased bronchodilator use. There was a negative correlation between the percent change in pre- to post-exercise FEV1 and salivary progesterone concentration. However, no such correlation was found between salivary estradiol and the percentage
change in pre- to post-exercise FEV1. This study has shown for the first time that menstrual cycle phase is an important determinant of the severity of EIB in
female athletes with mild atopic asthma. Female asthmatic athletes may need to adjust their training and competition schedules
to their menstrual cycle and to consider the potential negative effects of the LUT phase of the menstrual cycle on exercise
performance. 相似文献
14.
Summary To study the effects of previous submaximal exercise on the ventilatory determination of the Aerobic Threshold (AeT), 16 men were subjected to three maximal exercise tests (standard test = ST, retest = RT, and test with previous exercise = TPE) on a cycle ergometer. The protocol for the three tests consisted of 3 min pedalling against 25 W, followed by increments of 25 W every minute until volitional fatigue. TPE was preceded by 10 min cycling at a power output corresponding to the AeT as determined in ST, followed by a recovery period pedalling against 25 W until
returned to values consistent with the initial
response to 25 W. AeT was determined from the gas exchange curves (ventilatory equivalent for O2, fraction of expired O2, excess of
, ventilation, and respiratory gas exchange ratio) printed every 30 s. The results showed good ST×RT reliability (r=0.89). TPE showed significantly higher AeT values (2.548±0.44 l·min–1) when compared with ST (2.049±0.33 l·min–1) and RT (2.083±0.30 l·min–1). There were no significant differences for the sub-threshold respiratory gas exchange ratios among the trials. The sub-threshold
response showed significantly higher values for TPE at power outputs above 50 W. It was concluded that the performance of previous exercise can increase the value for the ventilatory determination of the AeT due to a faster sub-threshold
response.Supported by fellowship number 3660/80-3, CAPES, Brazil 相似文献
15.
Kang J Mangine GT Ratamess NA Faigenbaum AD Hoffman JR 《European journal of applied physiology》2007,100(3):253-260
This investigation was undertaken to examine the influence of intensity fluctuation on metabolic responses during and after
exercise. Twenty-four males and 24 females were randomly assigned into one of the four groups consisting of 12 subjects of
equal gender. Each group performed one of four 30-min exercise protocols: (1) cycling at a constant power output of 75 W (P1),
(2) cycling with power output alternating between 50 and 100 W every 5 min (P2), (3) same as P2 except power output was alternated
in a reverse order (P3), and (4) same as P2 except power output was alternated between 25 and 125 W (P4). Each exercise session
was followed by a 25-min recovery and all protocols yielded the same mechanical work. Oxygen uptake (VO2), heart rate (HR), respiratory exchange ratio (RER), and plasma lactate concentrations ([La]) were measured at rest and during
exercise and recovery. Ratings of perceived exertion (RPE) were recorded during exercise only. During exercise, VO2, HR and RPE did not differ across the four protocols. RER was higher (P < 0.05) in P4 than P1 and P2. [La] was higher (P < 0.05) in P4 than P1 and P3. During recovery, VO2 were lower (P < 0.05) in P1 than P2, P3, and P4, while [La] was higher in P4 than P3. When the total workload was equated, intensity fluctuation
exerted no added effect upon metabolic responses during exercise, but provoked greater energy expenditure following exercise.
Reversing the order or increasing the magnitude of intensity fluctuation would not further alter metabolic consequences. 相似文献
16.
This study examined the effects of menstrual cycle phase on ventilatory control. Fourteen eumenorrheic women were studied in the early follicular (FP; 1-6 days) and mid-luteal (LP; 20-24 days) phase of the menstrual cycle. Blood for the determination of arterial PCO(2) (PaCO(2)) , plasma strong ion difference ([SID]), progesterone ([P(4)]), and 17beta-estradiol ([E(2)]) concentrations were obtained at rest. Subjects performed a CO(2) rebreathing procedure that included prior hyperventilation and maintenance of iso-oxia to evaluate central and peripheral chemoreflex, and nonchemoreflex drives to breathe. Resting PaCO(2) and [SID] were lower; minute ventilation (V (E)), [P(4)] and [E(2)] were higher in the LP versus FP. Within the LP, significant correlations were observed for PaCO(2) with [P(4)], [E(2)] and [SID]. Menstrual cycle phase had no effect on the threshold or sensitivity of the central and/or peripheral ventilatory chemoreflex response to CO(2). Both (V (E)) and the ventilatory response to hypocapnia (representing nonchemoreflex drives to breathe) were approximately 1L/min greater in the LP versus FP accounting for the reduction in PaCO(2) . These data support the hypothesis that phasic menstrual cycle changes in PaCO(2) may be due, at least in part, to the stimulatory effects of [P(4)], [E(2)] and [SID] on ventilatory drive. 相似文献
17.
Ryszard Grucza Heikki Pekkarinen Eeva-Kaisa Titov Aulikki Kononoff Osmo Hänninen 《European journal of applied physiology》1993,67(3):279-285
Summary Thermoregulatory responses to exercise in relation to the phase of the menstrual cycle were studied in ten women taking oral contraceptives (P) and in ten women not taking oral contraceptives (NP). Each subject was tested for maximal aerobic capacity (
) and for 50%
exercise in the follicular (F) and luteal (L) phases of the menstrual cycle. Since the oral contraceptives would have prevented ovulation a quasi-follicular phase (q-F) and a quasi-luteal phase (q-L) of the menstrual cycle were assumed for P subjects. Exercise was performed on a cycle ergometer at an ambient temperature of 24° C and relative air humidity of 50%. Rectal (T
re), mean skin (
), mean body (
) temperatures and heart rate (f
c) were measured. Sweat rate was estimated by the continuous measurement of relative humidity of air in a ventilated capsule placed on the chest, converted to absolute pressure (PH2Ochest). Gain for sweating was calculated as a ratio of increase inPH2Ochest to the appropriate increase inT
re for the whole period of sweating (G) and for unsteady-state (Gu) separately. The
did not differ either between the groups of subjects or between the phases of the menstrual cycle. In P, rectal temperature threshold for sweating (T
re, td) was 37.85° C in q-L and 37.60° C in q-F (P < 0.01) and corresponded to a significant difference fromT
re at rest. TheT
re,
andf
c increased similarly during exercise in q-F and q-L. No menstrual phase-related differences were observed either in the dynamics of sweating or in G. In NP,T
re, td was shorter in L than in F (37.70 vs 37.47° C,P<0.02) with a significantly greater value fromT
re at rest. The dynamics and G for sweating were also greater in L than in F. The Gu was 36.8 versus 16.6 kPa · ° C–1 (P<0.01) while G was 6.4 versus 3.8 kPa · ° C–1 (P<0.05), respectively. TheT
re,
andf
c increased significantly more in phase F than in phase L. It was concluded that in these women performing moderate exercise, there was a greater temperature threshold and larger gains for sweating in phase L than in phase F. Intake of oral contraceptives reduced the differences in the gains for sweating making the thermoregulatory responses to exercise more uniform. 相似文献
18.
Christopher Ring Jet J.C.S. Veldhuijzen van Zanten Maria Kavussanu 《Biological psychology》2009,81(3):189-191
Sex differences in pain have been noted; women typically report more pain than men. Gonadal hormones may influence pain reports, and, moreover, such hormones may help to explain sex differences and menstrual cycle differences in pain. This study measured venipuncture and intravenous catherization pain during the follicular and luteal phases of the menstrual cycle in regularly menstruating women. Pain was also assessed in a group of men. Pain ratings were higher in women than men. In women, pain ratings did not differ between the follicular and luteal phases. Estradiol and progesterone increased from follicular to luteal phases. Within-phase analyses revealed that pain ratings were positively correlated with estradiol and progesterone during the luteal phase. Moreover, increases in estradiol and progesterone across the menstrual cycle were positively correlated with increases in pain. These findings suggest that variations in gonadal hormones during the menstrual cycle influence the experience of pain in healthy women. 相似文献
19.
Objectives: To evaluate the effects of endogenous estrogens and progestins on the IGF-system during the normal menstrual cycle in healthy premenopausal women not using contraceptive drugs. Methods: Nine women had fasting blood samples obtained at 2–3 days intervals during a 5 week study period. Plasma levels of IGF-I, IGF-II, IGFBP-1, IGFBP-3, estradiol and progesterone were measured by radioimmunoassay (RIA) in each sample. IGFBP-3 was also evaluated by Western ligand blot (WLB) and immunoblot. Any differences between the menstrual phase (defined as day 1–5), follicular and luteal phases (separation based on plasma estradiol and progesterone values) were evaluated by the Friedman test. Results: A small but significant difference in plasma levels of IGF-I (P<0.01) and IGFBP-3 (P<0.05) measured by RIA between the three phases were seen with the highest levels found during the follicular phase. No change in plasma levels of IGFBP-1 and IGF-II was found and immunoblots did not reveal any alteration in the ratio of fragmented to intact IGFBP-3 during the menstrual cycle. A positive correlation between plasma levels of IGF-I and estradiol was seen in 8 out of 9 patients (P=0.012). Conclusions: The finding of a slight but significant higher level of plasma IGF-I in the follicular and luteal phases compared with the menstrual phase suggests plasma estradiol may influence the level of this growth factor. This hypothesis is further supported by the finding of a correlation between plasma levels of IGF-I and estradiol but not progesterone in individual patients at different times during the menstrual cycle. 相似文献
20.
Stephen H. Boutcher Richard L. Seip Ronald K. Hetzler Edgar F. Pierce David Snead Arthur Weltman 《European journal of applied physiology》1989,59(5):365-369
Summary To determine the effects of cycle and run training on rating of perceived exertion at the lactate threshold (LT), college
men completed a 40-session training program in 10 weeks (n=6 run training,n=5 cycle training,n=5 controls). Pre-and post-training variables were measured during graded exercise tests on both the bicycle ergometer and
treadmill. ANOVA on the pre- and post-training difference scores resulted in similar improvements in
for both testing protocols, regardless of training mode. The run training group increased
at the LT by 58.5% on the treadmill protocol and by 20.3% on the cycle ergometer. Cycle trainers increased
LT only during cycle ergometry (+38.7%). No changes were observed in the control group. No differences for RPE at the LT
were found before or after training, or between testing protocols for any group. Perception of exercise intensity at the LT
ranged from “very light” to “light”. The relationship between RPE and
was altered by the specific mode of training, with trained subjects having a lower RPE at a given
(no change in RPE at max.). It was concluded that RPE at the LT was not affected by training, despite the fact that after
training the LT occurs at a higher work rate and was associated with higher absolute and relative metabolic and cardiorespiratory
demands. 相似文献