American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2000
We investigated the ability of exercise, a multipathway, potent, physiological stimulus for GH re... more We investigated the ability of exercise, a multipathway, potent, physiological stimulus for GH release, to alter the synergistic interaction of l-arginine (A) and GH-related peptide (GHRP)-2 (G) observed at rest and the ability of gender to further modulate this putative interaction. Subjects (9 men and 9 early follicular phase women) completed 30 min of constant load aerobic exercise in combination with intravenous infusions of saline (S), A (30 g over 30 min), G (1 μg/kg bolus), or both (AG) in separate study sessions in randomly assigned order. Measures of GH release were logarithmically transformed for statistical analysis. Similar to rest, exercise maintained the rank order (AG > G > A > S) of effective stimulation of GH release for the key response measures in men or women, a gender disparity in the time to reach the maximal serum GH concentration, the calculated endogenous GH half-life, and the observed effect of preinfusion (basal) serum GH concentrations on determi...
Background The work organization of long-haul truck drivers in the USA contains factors that have... more Background The work organization of long-haul truck drivers in the USA contains factors that have been shown to degrade sleep. In combination, these factors generate elevated cardiometabolic risk by inducing components of the metabolic syndrome (MetS). However, the prevalence and severity of MetS and the degree to which such factors differentially influence MetS among these drivers are unknown. Aims To determine the prevalence and severity of MetS among US long-haul truck drivers and to determine the predictive value of demographic, work organization and sleep variables in MetS diagnosis and severity. Methods A non-experimental, descriptive, cross-sectional study, designed to collect survey, anthropometric and biometric data from US long-haul truck drivers. Descriptive analyses were performed for demographic, work organization, sleep and MetS measures. Logistic and linear regression analyses examined potential predictive relationships between demographic, work organization and sleep variables and MetS diagnosis and severity. Results The study population was 262. Nearly 60% of drivers met MetS diagnosis criteria. Over 80% had a waist circumference >102 cm, 50% had triglyceride levels of ≥150 mg/dl, 66% had an high-density lipoprotein of <40 mg/dl, 28% had a blood pressure of ≥135/80 mm Hg and 17% had a fasting glucose of ≥110 mg/dl. Driving experience and work day sleep quality were associated with MetS prevalence and severity. Conclusions The prevalence and severity of MetS among this sample of US long-haul truck drivers were high. Preventive efforts should focus on experienced drivers and work day sleep quality.
Background: Sex steroid hormone fluctuations during the menstrual cycle are considered a risk fac... more Background: Sex steroid hormone fluctuations during the menstrual cycle are considered a risk factor for noncontact anterior cruciate ligament injuries. Objective: To determine whether self-reported menstrual history data can be used to accurately categorize menstrual cycle events using calendar-based counting methods. Study Design: Descriptive laboratory study. Methods: Seventy-three women completed a menstrual history questionnaire and submitted to blood sampling for the first 6 days of menses and 8 to 10 days after a positive ovulation test over 2 consecutive months. Frequency counts determined whether appropriate criterion hormone (progesterone) levels were achieved at predefined calendar days. Results: For the criterion of progesterone >2 ng/mL, 18% and 59% of women attained it when counting forward 10 to 14 days after the onset of menses and counting back 12 to 14 days from the end of the cycle, respectively. Most women (76%) attained the criterion for ovulation 1 to 3 days...
Background: Genetic association studies demonstrate a relationship between several collagen gene ... more Background: Genetic association studies demonstrate a relationship between several collagen gene variants and anterior cruciate ligament (ACL) injury, yet the mechanism of these relationships is still unclear. Joint laxity is a heritable trait; increased magnitudes of anterior knee laxity (AKL), genu recurvatum (GR), and general joint laxity (GJL) have been consistently associated with a greater risk of ACL injury. Joint laxity may constitute an important intermediate phenotype for the genetic association with ACL injury that can be measured clinically. Hypothesis: To determine if genetic variants within the COL1A1, COL5A1, and COL12A1 genes, previously associated with ACL injury, were also associated with greater magnitudes of AKL, GR, and GJL. Study Design: Descriptive laboratory study. Methods: Blood samples and measures of AKL, GR, and GJL were obtained from 124 (50 male, 74 female) healthy, recreationally active subjects. Genomic DNA was extracted from the blood samples and gen...
Purpose: Less lean body mass may limit one's ability to produce adequate muscle forces to safely ... more Purpose: Less lean body mass may limit one's ability to produce adequate muscle forces to safely control landing from a jump, thus increasing the risk for injury. The primary objective of this study was to determine the effect of lower extremity lean mass (LELM) and eccentric muscle strength on lower extremity energy absorption (EA) during a drop jump landing. Methods: Seventy athletic subjects (35 men and 35 women) were measured for LELM with dual-energy x-ray absorptiometry, maximal eccentric strength of the quadriceps (QuadECC) and hamstrings (HamECC), and lower extremity joint energetics during the initial landing of a drop jump. A mediation analysis examined the extent to which LELM predicted EA at each lower extremity joint (EAHIP, EAKNEE, and EAANK) and subsequently whether these relationships were mediated by each subject's maximal eccentric strength capabilities. Results: LELM was a significant predictor of EAKNEE (R 2 = 0.22, P < 0.01) in females but not in males (R 2 = 0.03, P = 0.16). In females, QuadECC was a significant mediator of the effect of LELM on EA at the knee (ab = 179.72, 95% confidence interval [CI] = 10.43-423.42) and ankle (ab = 1.71, 95% CI = [0.16, 3.94]), whereas HamECC was a significant mediator of the relationship between LELM and EAHIP (ab = 4.89, 95% CI = 2.05-8.40). No significant relationships were observed in males. Conclusions: LELM was a significant factor in energetic capabilities for females but not males. For females, this relationship was evident secondary to the stronger underlying relationship between maximal strength and EA. Thus, the maximal eccentric strength capabilities may be a more important determinant of energetic behaviors compared with the available quantity of lean mass alone. More work is needed to investigate these relationships and to reveal the underlying sex-specific mechanisms that determine EA capabilities.
Variations in serum markers of collagen production (CICP) and degradation (ICTP), insulin-like gr... more Variations in serum markers of collagen production (CICP) and degradation (ICTP), insulin-like growth factor I (IGF-I) and anterior knee laxity (AKL) were measured in 20 women [10 with spontaneous cycles (eumenorrheic), 10 using oral contraceptives] over 5 consecutive days at menses (M1-M5, 1st pill week), the initial estrogen rise near ovulation (O1-O5, 2nd pill week), the initial progesterone rise of the early luteal phase (EL1-EL5, 3rd pill week) and postprogesterone peak of the late luteal phase (LL1-LL5, 4th pill week). ICTP was higher in oral contraceptive women (5.3 ± 1.7 vs. 3.7 ± 1.3 µg/L; p = 0.030), primarily during days near ovulation and the early luteal phase when concentrations decreased in eumenorrheic women (p = 0.04). IGF-I concentrations increased during menses then decreased and remained lower during the early and late luteal phase in oral contraceptive women, resulting in lower concentrations compared to eumenorrheic women at EL2 and LL1 (p = 0.03). CICP decreased in early and late luteal days (p <0.01), and there was a trend toward lower concentrations in eumenorrheic versus oral contraceptive women (85.7 ± 35.7 ng/ml vs. 123.2 ± 49.8 ng/ml; p = 0.07). Lower CICP and greater IGF-I concentrations predicted greater AKL across the 20 cycle days in both groups (R 2 = 0.310 and 0.400). Sex hormone concentration changes across the menstrual cycle are of sufficient magnitude to influence collagen metabolism, and may indirectly influence knee structure and function.
Age, body composition, exercise and gender influence growth hormone (GH) secretion. However, litt... more Age, body composition, exercise and gender influence growth hormone (GH) secretion. However, little is known about the relationship between GH release during a single bout of acute aerobic exercise (AAE) and its relationship to GH secretion over a 24-hour period without an external stimulus (CON). PURPOSE: To investigate if exercise-induced GH release during AAE is related to GH release during CON and how age, body composition, and gender influence this relationship. METHODS: Secondary analysis of data from 29 volunteers (n=16 males, n=13 females) ranging from 17.0-40.0 yrs, was completed. Briefly, VO2peak and lactate threshold (LT) were determined from a continuously graded cycle ergometer test until volitional fatigue using open circuit spirometry (Viasys Vmax 229, Yorba Linda, CA.) Subjects were admitted to the University of Virginia General Clinical Research Center the evening before testing. Blood samples were taken every 10 minutes [Q10] during rest and exercise starting at 0700 h until the next day. The exercise stimulus consisted of one 30-min session with a relative power output set midway between VO2 at LT and VO2peak. GH area under the curve (AUC) was calculated using trapezoidal integration for 24 hours as well as the 30-minute exercise session. All statistics were run on log-transformed data and P values were reported for confidence intervals of the geometric means. RESULTS: Simultaneous multiple regression analysis in men revealed that 24-hour GH AUC was best predicted by BMI and age (r2 = 0.64, P < 0.001) and in women 24-hour GH AUC was best predicted by GH secretion during 30 minutes of exercise, BMI and age (r2 = 0.91, P < 0.001). Overall, 24-hr GH AUC in males and females was related to age (r2 = 0.31 and 0.31), BMI (r2 = 0.50 and 0.60,) GH secretion during 30 minutes of exercise (r2 = 0.45 and 0.83), and peak GH secretion during exercise (r2 = 0.17 and 0.63) respectively. CONCLUSION: Consistent with previously reported literature, body mass and age were related to 24-hour GH AUC. In men, exercise-induced GH release does not provide significant information about 24-hr GH output. However, in women exercise-induced GH release during AAE does provide important information related to 24-hr GH output. These findings suggest that exercise is particularly important for increasing GH output in women.
Purpose-It is unclear whether sex hormone profiles obtained in two consecutive months are consist... more Purpose-It is unclear whether sex hormone profiles obtained in two consecutive months are consistent within women. Month-to-month consistency in daily, nadir, peak and mean hormone concentrations during the early follicular and luteal phases in recreationally active, young eumenorrheic women was prospectively examined. Methods-60 healthy, non-smoking women who reported normal and consistent menstrual cycles lasting 26-32 days for the past 6 months were followed prospectively to obtain serum samples for the first 6 days of menses and for 8 days after a positive ovulation test over two consecutive months. Month-to-month consistency of daily concentrations of oestradiol (pg/ml), progesterone (ng/ml), testosterone (ng/dl), sex hormone-binding globulin (nmol/l) and free androgen index were determined using linear mixed models. Month-to-month consistency in nadir, peak and mean concentrations were then assessed using intraclass correlation coefficients and SEM to more precisely examine intraindividual consistency. Results-Linear mixed models revealed stable hormone concentrations across cycles and cycles by day. Reliability estimates for nadir, peak, mean menses and mean postovulatory concentrations range from 0.56 to 0.86 for oestradiol, 0.44 to 0.91 for progesterone, 0.60 to 0.86 for testosterone, 0.88 to 0.97 for sex hormone-binding globulin and 0.78 to 0.91 for free androgen index. Conclusions-Hormone profiles were reproducible over two consecutive months. To reduce month-to-month intraindividual variations and improve measurement consistency, it is recommended that multiple samples be taken over consecutive days as opposed to a single sample. Article: Variations in sex hormone concentrations in young, physically active women may be associated with the risk of non-contact anterior cruciate ligament (ACL) injury. Studies report a greater number of injuries than expected during the perimenstrual 1-3 and periovulatory 4 5 days, whereas others generally identified the follicular phase as being the phase of higher risk. 6 7 These studies collected a single sample (blood or urine) shortly after the injury (range 2 h 7 to 72 h 2), making it difficult to identify the specific time in a particular phase when injury occurred (ie, whether hormone levels were rising, falling or near their peak). Other work suggests a time delay
The Journal of sports medicine and physical fitness, 1996
OBJECTIVE The purpose of this study was to assess differences in measures of postprandial triglyc... more OBJECTIVE The purpose of this study was to assess differences in measures of postprandial triglyceride (TG) clearance between obese men with abdominal fat patterning (OAF) and men of desirable weight (DW). It was hypothesized that the OAF men would have impaired postprandial TG clearance. EXPERIMENTAL DESIGN A comparative design was used. SETTING Data were collected in a research laboratory with access to blood analysis instrumentation. PARTICIPANTS Fourteen healthy, physically active, normolipemic men (7 OAF and 7 DW) were studied. INTERVENTIONS Each subject consumed an oral fat load (78 grams of fat) and blood samples were collected every hour for 8 hours. MEASURES Measures of postprandial lipemia included: incremental TG area, total TG area, time to peak TG concentration, maximal change in TG concentration, and time to return to baseline TG concentration. RESULTS OAF men had significantly greater total area under the TG curve (24.7 +/- 1.09 vs 16.1 +/- 1.3 mmol-L(-1).8 hours, p =...
Pancreas transplantation has gained clinical acceptance since its initial application more than 3... more Pancreas transplantation has gained clinical acceptance since its initial application more than 30 years ago. A constellation of surgical, pharmacologic, and metabolic alterations occur with transplantation, particularly if pancreatic transplantation is performed in addition to renal transplantation in a uremic diabetic. Increasingly sophisticated studies have allowed analysis of the performance of the transplanted organ and have enhanced our basic understanding of insulin's complex interplay in peripheral glucoregulatory processes. Article: Clinical experience with pancreas transplantation was not overwhelmingly successful during the late 1960s and early 1970s [1]. Over the next 20 years a period of constant reevaluation and reassessment of early clinical failures resulted in the development of animal models of transplantation. These models ultimately led to advances in surgical techniques and immunosuppression therapy and provided a better understanding of the impact of surgically induced alterations to the pancreas on carbohydrate metabolism. As pancreas transplantation enjoyed an increasing success rate and longer patient survival, posttransplant graft physiology and the metabolic response to the new insulin source became an interesting area of research. EARLY MODELS OF TRANSPLANTATION Surgical alterations of the pancreas that occur during transplantation include (1) reduction of the beta cell mass (by resection, immunologic loss, or preservation ischemic loss); (2) systemic venous drainage versus portal venous drainage of the pancreatic venous effluent; and (3) denervation. Surgical alterations per se should lead to an altered insulin source. What effect, if any, might this have on peripheral levels of insulin or insulin's glucoregulatory properties? Would it ultimately affect the function of the transplanted pancreas? To address these questions and attempt to delineate the role of surgical alterations of the pancreas on longterm glucose homeostasis in transplanted patients, studies were performed using primarily dog or rat models. Reduction of Beta Cell Mass The complex interplay between insulin secretion and insulin action was suggested nearly 50 years ago by Dragstedt et al.'s observation that the amount of insulin required to control glucosuria after partial pancreatectomy exceeded the amount needed after complete pancreatectomy [2]. Subsequently, it became evident that surgical models of partial pancreatectomy might result in alterations of alpha and beta cell ratios, which could explain earlier observations. Studies evaluating a dog model of 60% to 80% partial pancreatectomy showed that these animals have a reduced insulin response to the intravenous glucose tolerance test (IVGTT) and altered potassium values, indicating altered glucose metabolism [3]. It was suggested that
Physical activity is predictive of better cognitive performance and lower risk of Alzheimer&a... more Physical activity is predictive of better cognitive performance and lower risk of Alzheimer&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s disease (AD). The apolipoprotein E gene (APOE) is a susceptibility gene for AD with the e4 allele being associated with a greater risk of AD. Cross-sectional and prospective research shows that physical activity is predictive of better cognitive performance for those at greater genetic risk for AD. However, the moderating role of APOE on the effects of a physical activity intervention on cognitive performance has not been examined. The purpose of this manuscript is to justify the need for such research and to describe the design, methods, and recruitment tactics used in the conductance of a study designed to provide insight as to the extent to which cognitive benefits resulting from an 8-month physical activity program are differentiated by ApoEe4 status. The effectiveness of the recruitment strategies and the feasibility of recruiting ApoE e4 carriers are discussed.
American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2000
We investigated the ability of exercise, a multipathway, potent, physiological stimulus for GH re... more We investigated the ability of exercise, a multipathway, potent, physiological stimulus for GH release, to alter the synergistic interaction of l-arginine (A) and GH-related peptide (GHRP)-2 (G) observed at rest and the ability of gender to further modulate this putative interaction. Subjects (9 men and 9 early follicular phase women) completed 30 min of constant load aerobic exercise in combination with intravenous infusions of saline (S), A (30 g over 30 min), G (1 μg/kg bolus), or both (AG) in separate study sessions in randomly assigned order. Measures of GH release were logarithmically transformed for statistical analysis. Similar to rest, exercise maintained the rank order (AG > G > A > S) of effective stimulation of GH release for the key response measures in men or women, a gender disparity in the time to reach the maximal serum GH concentration, the calculated endogenous GH half-life, and the observed effect of preinfusion (basal) serum GH concentrations on determi...
Background The work organization of long-haul truck drivers in the USA contains factors that have... more Background The work organization of long-haul truck drivers in the USA contains factors that have been shown to degrade sleep. In combination, these factors generate elevated cardiometabolic risk by inducing components of the metabolic syndrome (MetS). However, the prevalence and severity of MetS and the degree to which such factors differentially influence MetS among these drivers are unknown. Aims To determine the prevalence and severity of MetS among US long-haul truck drivers and to determine the predictive value of demographic, work organization and sleep variables in MetS diagnosis and severity. Methods A non-experimental, descriptive, cross-sectional study, designed to collect survey, anthropometric and biometric data from US long-haul truck drivers. Descriptive analyses were performed for demographic, work organization, sleep and MetS measures. Logistic and linear regression analyses examined potential predictive relationships between demographic, work organization and sleep variables and MetS diagnosis and severity. Results The study population was 262. Nearly 60% of drivers met MetS diagnosis criteria. Over 80% had a waist circumference >102 cm, 50% had triglyceride levels of ≥150 mg/dl, 66% had an high-density lipoprotein of <40 mg/dl, 28% had a blood pressure of ≥135/80 mm Hg and 17% had a fasting glucose of ≥110 mg/dl. Driving experience and work day sleep quality were associated with MetS prevalence and severity. Conclusions The prevalence and severity of MetS among this sample of US long-haul truck drivers were high. Preventive efforts should focus on experienced drivers and work day sleep quality.
Background: Sex steroid hormone fluctuations during the menstrual cycle are considered a risk fac... more Background: Sex steroid hormone fluctuations during the menstrual cycle are considered a risk factor for noncontact anterior cruciate ligament injuries. Objective: To determine whether self-reported menstrual history data can be used to accurately categorize menstrual cycle events using calendar-based counting methods. Study Design: Descriptive laboratory study. Methods: Seventy-three women completed a menstrual history questionnaire and submitted to blood sampling for the first 6 days of menses and 8 to 10 days after a positive ovulation test over 2 consecutive months. Frequency counts determined whether appropriate criterion hormone (progesterone) levels were achieved at predefined calendar days. Results: For the criterion of progesterone >2 ng/mL, 18% and 59% of women attained it when counting forward 10 to 14 days after the onset of menses and counting back 12 to 14 days from the end of the cycle, respectively. Most women (76%) attained the criterion for ovulation 1 to 3 days...
Background: Genetic association studies demonstrate a relationship between several collagen gene ... more Background: Genetic association studies demonstrate a relationship between several collagen gene variants and anterior cruciate ligament (ACL) injury, yet the mechanism of these relationships is still unclear. Joint laxity is a heritable trait; increased magnitudes of anterior knee laxity (AKL), genu recurvatum (GR), and general joint laxity (GJL) have been consistently associated with a greater risk of ACL injury. Joint laxity may constitute an important intermediate phenotype for the genetic association with ACL injury that can be measured clinically. Hypothesis: To determine if genetic variants within the COL1A1, COL5A1, and COL12A1 genes, previously associated with ACL injury, were also associated with greater magnitudes of AKL, GR, and GJL. Study Design: Descriptive laboratory study. Methods: Blood samples and measures of AKL, GR, and GJL were obtained from 124 (50 male, 74 female) healthy, recreationally active subjects. Genomic DNA was extracted from the blood samples and gen...
Purpose: Less lean body mass may limit one's ability to produce adequate muscle forces to safely ... more Purpose: Less lean body mass may limit one's ability to produce adequate muscle forces to safely control landing from a jump, thus increasing the risk for injury. The primary objective of this study was to determine the effect of lower extremity lean mass (LELM) and eccentric muscle strength on lower extremity energy absorption (EA) during a drop jump landing. Methods: Seventy athletic subjects (35 men and 35 women) were measured for LELM with dual-energy x-ray absorptiometry, maximal eccentric strength of the quadriceps (QuadECC) and hamstrings (HamECC), and lower extremity joint energetics during the initial landing of a drop jump. A mediation analysis examined the extent to which LELM predicted EA at each lower extremity joint (EAHIP, EAKNEE, and EAANK) and subsequently whether these relationships were mediated by each subject's maximal eccentric strength capabilities. Results: LELM was a significant predictor of EAKNEE (R 2 = 0.22, P < 0.01) in females but not in males (R 2 = 0.03, P = 0.16). In females, QuadECC was a significant mediator of the effect of LELM on EA at the knee (ab = 179.72, 95% confidence interval [CI] = 10.43-423.42) and ankle (ab = 1.71, 95% CI = [0.16, 3.94]), whereas HamECC was a significant mediator of the relationship between LELM and EAHIP (ab = 4.89, 95% CI = 2.05-8.40). No significant relationships were observed in males. Conclusions: LELM was a significant factor in energetic capabilities for females but not males. For females, this relationship was evident secondary to the stronger underlying relationship between maximal strength and EA. Thus, the maximal eccentric strength capabilities may be a more important determinant of energetic behaviors compared with the available quantity of lean mass alone. More work is needed to investigate these relationships and to reveal the underlying sex-specific mechanisms that determine EA capabilities.
Variations in serum markers of collagen production (CICP) and degradation (ICTP), insulin-like gr... more Variations in serum markers of collagen production (CICP) and degradation (ICTP), insulin-like growth factor I (IGF-I) and anterior knee laxity (AKL) were measured in 20 women [10 with spontaneous cycles (eumenorrheic), 10 using oral contraceptives] over 5 consecutive days at menses (M1-M5, 1st pill week), the initial estrogen rise near ovulation (O1-O5, 2nd pill week), the initial progesterone rise of the early luteal phase (EL1-EL5, 3rd pill week) and postprogesterone peak of the late luteal phase (LL1-LL5, 4th pill week). ICTP was higher in oral contraceptive women (5.3 ± 1.7 vs. 3.7 ± 1.3 µg/L; p = 0.030), primarily during days near ovulation and the early luteal phase when concentrations decreased in eumenorrheic women (p = 0.04). IGF-I concentrations increased during menses then decreased and remained lower during the early and late luteal phase in oral contraceptive women, resulting in lower concentrations compared to eumenorrheic women at EL2 and LL1 (p = 0.03). CICP decreased in early and late luteal days (p <0.01), and there was a trend toward lower concentrations in eumenorrheic versus oral contraceptive women (85.7 ± 35.7 ng/ml vs. 123.2 ± 49.8 ng/ml; p = 0.07). Lower CICP and greater IGF-I concentrations predicted greater AKL across the 20 cycle days in both groups (R 2 = 0.310 and 0.400). Sex hormone concentration changes across the menstrual cycle are of sufficient magnitude to influence collagen metabolism, and may indirectly influence knee structure and function.
Age, body composition, exercise and gender influence growth hormone (GH) secretion. However, litt... more Age, body composition, exercise and gender influence growth hormone (GH) secretion. However, little is known about the relationship between GH release during a single bout of acute aerobic exercise (AAE) and its relationship to GH secretion over a 24-hour period without an external stimulus (CON). PURPOSE: To investigate if exercise-induced GH release during AAE is related to GH release during CON and how age, body composition, and gender influence this relationship. METHODS: Secondary analysis of data from 29 volunteers (n=16 males, n=13 females) ranging from 17.0-40.0 yrs, was completed. Briefly, VO2peak and lactate threshold (LT) were determined from a continuously graded cycle ergometer test until volitional fatigue using open circuit spirometry (Viasys Vmax 229, Yorba Linda, CA.) Subjects were admitted to the University of Virginia General Clinical Research Center the evening before testing. Blood samples were taken every 10 minutes [Q10] during rest and exercise starting at 0700 h until the next day. The exercise stimulus consisted of one 30-min session with a relative power output set midway between VO2 at LT and VO2peak. GH area under the curve (AUC) was calculated using trapezoidal integration for 24 hours as well as the 30-minute exercise session. All statistics were run on log-transformed data and P values were reported for confidence intervals of the geometric means. RESULTS: Simultaneous multiple regression analysis in men revealed that 24-hour GH AUC was best predicted by BMI and age (r2 = 0.64, P < 0.001) and in women 24-hour GH AUC was best predicted by GH secretion during 30 minutes of exercise, BMI and age (r2 = 0.91, P < 0.001). Overall, 24-hr GH AUC in males and females was related to age (r2 = 0.31 and 0.31), BMI (r2 = 0.50 and 0.60,) GH secretion during 30 minutes of exercise (r2 = 0.45 and 0.83), and peak GH secretion during exercise (r2 = 0.17 and 0.63) respectively. CONCLUSION: Consistent with previously reported literature, body mass and age were related to 24-hour GH AUC. In men, exercise-induced GH release does not provide significant information about 24-hr GH output. However, in women exercise-induced GH release during AAE does provide important information related to 24-hr GH output. These findings suggest that exercise is particularly important for increasing GH output in women.
Purpose-It is unclear whether sex hormone profiles obtained in two consecutive months are consist... more Purpose-It is unclear whether sex hormone profiles obtained in two consecutive months are consistent within women. Month-to-month consistency in daily, nadir, peak and mean hormone concentrations during the early follicular and luteal phases in recreationally active, young eumenorrheic women was prospectively examined. Methods-60 healthy, non-smoking women who reported normal and consistent menstrual cycles lasting 26-32 days for the past 6 months were followed prospectively to obtain serum samples for the first 6 days of menses and for 8 days after a positive ovulation test over two consecutive months. Month-to-month consistency of daily concentrations of oestradiol (pg/ml), progesterone (ng/ml), testosterone (ng/dl), sex hormone-binding globulin (nmol/l) and free androgen index were determined using linear mixed models. Month-to-month consistency in nadir, peak and mean concentrations were then assessed using intraclass correlation coefficients and SEM to more precisely examine intraindividual consistency. Results-Linear mixed models revealed stable hormone concentrations across cycles and cycles by day. Reliability estimates for nadir, peak, mean menses and mean postovulatory concentrations range from 0.56 to 0.86 for oestradiol, 0.44 to 0.91 for progesterone, 0.60 to 0.86 for testosterone, 0.88 to 0.97 for sex hormone-binding globulin and 0.78 to 0.91 for free androgen index. Conclusions-Hormone profiles were reproducible over two consecutive months. To reduce month-to-month intraindividual variations and improve measurement consistency, it is recommended that multiple samples be taken over consecutive days as opposed to a single sample. Article: Variations in sex hormone concentrations in young, physically active women may be associated with the risk of non-contact anterior cruciate ligament (ACL) injury. Studies report a greater number of injuries than expected during the perimenstrual 1-3 and periovulatory 4 5 days, whereas others generally identified the follicular phase as being the phase of higher risk. 6 7 These studies collected a single sample (blood or urine) shortly after the injury (range 2 h 7 to 72 h 2), making it difficult to identify the specific time in a particular phase when injury occurred (ie, whether hormone levels were rising, falling or near their peak). Other work suggests a time delay
The Journal of sports medicine and physical fitness, 1996
OBJECTIVE The purpose of this study was to assess differences in measures of postprandial triglyc... more OBJECTIVE The purpose of this study was to assess differences in measures of postprandial triglyceride (TG) clearance between obese men with abdominal fat patterning (OAF) and men of desirable weight (DW). It was hypothesized that the OAF men would have impaired postprandial TG clearance. EXPERIMENTAL DESIGN A comparative design was used. SETTING Data were collected in a research laboratory with access to blood analysis instrumentation. PARTICIPANTS Fourteen healthy, physically active, normolipemic men (7 OAF and 7 DW) were studied. INTERVENTIONS Each subject consumed an oral fat load (78 grams of fat) and blood samples were collected every hour for 8 hours. MEASURES Measures of postprandial lipemia included: incremental TG area, total TG area, time to peak TG concentration, maximal change in TG concentration, and time to return to baseline TG concentration. RESULTS OAF men had significantly greater total area under the TG curve (24.7 +/- 1.09 vs 16.1 +/- 1.3 mmol-L(-1).8 hours, p =...
Pancreas transplantation has gained clinical acceptance since its initial application more than 3... more Pancreas transplantation has gained clinical acceptance since its initial application more than 30 years ago. A constellation of surgical, pharmacologic, and metabolic alterations occur with transplantation, particularly if pancreatic transplantation is performed in addition to renal transplantation in a uremic diabetic. Increasingly sophisticated studies have allowed analysis of the performance of the transplanted organ and have enhanced our basic understanding of insulin's complex interplay in peripheral glucoregulatory processes. Article: Clinical experience with pancreas transplantation was not overwhelmingly successful during the late 1960s and early 1970s [1]. Over the next 20 years a period of constant reevaluation and reassessment of early clinical failures resulted in the development of animal models of transplantation. These models ultimately led to advances in surgical techniques and immunosuppression therapy and provided a better understanding of the impact of surgically induced alterations to the pancreas on carbohydrate metabolism. As pancreas transplantation enjoyed an increasing success rate and longer patient survival, posttransplant graft physiology and the metabolic response to the new insulin source became an interesting area of research. EARLY MODELS OF TRANSPLANTATION Surgical alterations of the pancreas that occur during transplantation include (1) reduction of the beta cell mass (by resection, immunologic loss, or preservation ischemic loss); (2) systemic venous drainage versus portal venous drainage of the pancreatic venous effluent; and (3) denervation. Surgical alterations per se should lead to an altered insulin source. What effect, if any, might this have on peripheral levels of insulin or insulin's glucoregulatory properties? Would it ultimately affect the function of the transplanted pancreas? To address these questions and attempt to delineate the role of surgical alterations of the pancreas on longterm glucose homeostasis in transplanted patients, studies were performed using primarily dog or rat models. Reduction of Beta Cell Mass The complex interplay between insulin secretion and insulin action was suggested nearly 50 years ago by Dragstedt et al.'s observation that the amount of insulin required to control glucosuria after partial pancreatectomy exceeded the amount needed after complete pancreatectomy [2]. Subsequently, it became evident that surgical models of partial pancreatectomy might result in alterations of alpha and beta cell ratios, which could explain earlier observations. Studies evaluating a dog model of 60% to 80% partial pancreatectomy showed that these animals have a reduced insulin response to the intravenous glucose tolerance test (IVGTT) and altered potassium values, indicating altered glucose metabolism [3]. It was suggested that
Physical activity is predictive of better cognitive performance and lower risk of Alzheimer&a... more Physical activity is predictive of better cognitive performance and lower risk of Alzheimer&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s disease (AD). The apolipoprotein E gene (APOE) is a susceptibility gene for AD with the e4 allele being associated with a greater risk of AD. Cross-sectional and prospective research shows that physical activity is predictive of better cognitive performance for those at greater genetic risk for AD. However, the moderating role of APOE on the effects of a physical activity intervention on cognitive performance has not been examined. The purpose of this manuscript is to justify the need for such research and to describe the design, methods, and recruitment tactics used in the conductance of a study designed to provide insight as to the extent to which cognitive benefits resulting from an 8-month physical activity program are differentiated by ApoEe4 status. The effectiveness of the recruitment strategies and the feasibility of recruiting ApoE e4 carriers are discussed.
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