Low carbohydrate high fat ketogenic diets on the exercise crossover point and glucose homeostasis.

In exercise science, the crossover effect denotes that fat oxidation is the primary fuel at rest and during low-intensity exercise with a shift towards an increased reliance on carbohydrate oxidation at moderate to high exercise intensities. This model makes four predictions: First, >50% of energy comes from carbohydrate oxidation at ≥60% of maximum oxygen consumption (VO2max), termed the crossover point. Second, each individual has a maximum fat oxidation capacity (FATMAX) at an exercise intensity lower than the crossover point. FATMAX values are typically 0.3-0.6 g/min. Third, fat oxidation is minimized during exercise ≥85%VO2max, making carbohydrates the predominant energetic substrate during high-intensity exercise, especially at >85%VO2max. Fourth, high-carbohydrate low-fat (HCLF) diets will produce superior exercise performances via maximizing pre-exercise storage of this predominant exercise substrate. In a series of recent publications evaluating the metabolic and performance effects of low-carbohydrate high-fat (LCHF/ketogenic) diet adaptations during exercise of different intensities, we provide findings that challenge this model and these four predictions. First, we show that adaptation to the LCHF diet shifts the crossover point to a higher %VO2max (>80%VO2max) than previously reported. Second, substantially higher FATMAX values (>1.5 g/min) can be measured in athletes adapted to the LCHF diet. Third, endurance athletes exercising at >85%VO2max, whilst performing 6 × 800 m running intervals, measured the highest rates of fat oxidation yet reported in humans. Peak fat oxidation rates measured at 86.4 ± 6.2%VO2max were 1.58 ± 0.33 g/min with 30% of subjects achieving >1.85 g/min. These studies challenge the prevailing doctrine that carbohydrates are the predominant oxidized fuel during high-intensity exercise. We recently found that 30% of middle-aged competitive athletes presented with pre-diabetic glycemic values while on an HCLF diet, which was reversed on LCHF. We speculate that these rapid changes between diet, insulin, glucose homeostasis, and fat oxidation might be linked by diet-induced changes in mitochondrial function and insulin action. Together, we demonstrate evidence that challenges the current crossover concept and demonstrate evidence that a LCHF diet may also reverse features of pre-diabetes and future metabolic disease risk, demonstrating the impact of dietary choice has extended beyond physical performance even in athletic populations.

Effect of resistance training on resting metabolic rate and its estimation by a dual-energy X-ray absorptiometry metabolic map.

BACKGROUND/OBJECTIVES: Fat-free mass (FFM) is the major predictor of resting metabolic rate (RMR). As protein supplementation during resistance training may augment gains in FFM, we investigated the effects of resistance training combined with protein supplementation on RMR and whether RMR responses could be estimated by a dual-energy X-ray absorptiometry (DXA) metabolic map. SUBJECTS/METHODS: Healthy adults completed a whole-body periodized resistance training program consisting of 96 workouts (~9 months). Participants were randomly assigned to supplement with whey protein (whey; n=18), soy protein (soy; n=21) or carbohydrate (carb; n=22). RMR was measured using indirect calorimetry (RMR(IC)) and estimated by DXA metabolic mapping (RMR(MM)) pretraining and posttraining. RESULTS: RMR(IC) increased from pretraining to posttraining in the whole cohort (1653±302 to 1726±291 kcal/day, P=0.001) without differences between the groups. Delta RMR(IC) and RMR(MM) (73±158 vs 52±41 kcal/day were not significantly different by t-test (P=0.303), although they were not significantly correlated (r=0.081; P=0.535). Stepwise regression identified 43% of the shared variance in delta RMR(IC) using total serum thyroxine, RMR(IC) and FFM at baseline (P=0.009). CONCLUSIONS: These results indicate that 9 months of resistance training significantly increased RMR ~5% on average, but there was wide variability between individuals, which can be partially accounted for by changes in FFM and thyroid hormones.

Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets.

Very-low-carbohydrate diets or ketogenic diets have been in use since the 1920s as a therapy for epilepsy and can, in some cases, completely remove the need for medication. From the 1960s onwards they have become widely known as one of the most common methods for obesity treatment. Recent work over the last decade or so has provided evidence of the therapeutic potential of ketogenic diets in many pathological conditions, such as diabetes, polycystic ovary syndrome, acne, neurological diseases, cancer and the amelioration of respiratory and cardiovascular disease risk factors. The possibility that modifying food intake can be useful for reducing or eliminating pharmaceutical methods of treatment, which are often lifelong with significant side effects, calls for serious investigation. This review revisits the meaning of physiological ketosis in the light of this evidence and considers possible mechanisms for the therapeutic actions of the ketogenic diet on different diseases. The present review also questions whether there are still some preconceived ideas about ketogenic diets, which may be presenting unnecessary barriers to their use as therapeutic tools in the physician's hand.

Carbohydrate restriction favorably alters lipoprotein metabolism in Emirati subjects classified with the metabolic syndrome.

BACKGROUND AND AIMS: Carbohydrate restriction (CR) has been shown to improve dyslipidemias associated with metabolic syndrome (MetS). We evaluated the effects of CR on lipoprotein subfractions and apolipoproteins in Emirati adults classified with the MetS. METHODS AND RESULTS: 39 subjects (15 men/24 women) were randomly allocated to a CR diet [20-25% energy from carbohydrate (CHO)] for 12 wk (CRD group) or a combination treatment consisting of CRD for 6 wk followed by the American Heart Association diet (50-55% CHO, AHA group) for an additional 6 wk. All subjects reduced body weight, LDL cholesterol and triglycerides (P<0.01). At baseline all subjects had low concentrations of medium VLDL and total HDL particles associated with the very low plasma triglycerides and HDL cholesterol in this population. After 12 wk, the large VLDL subfraction was decreased over time for subjects in the CRD group (P<0.01) while these changes were not observed in those subjects who changed to the AHA diet. The number of medium and small LDL particles decreased for all subjects rendering a less atherogenic lipoprotein profile. In agreement with these results, a significant decrease in apolipoprotein (apo) B was observed (P<0.01). The medium HDL subfraction and apo A-II, which can be considered pro-atherogenic, were also decreased over time in the CRD group only. CONCLUSIONS: These results suggest that weight loss favorably affects lipoprotein metabolism and that the CRD had a better effect on atherogenic VLDL and HDL than the low fat diet recommended by AHA.

Hormonal responses to a 160-km race across frozen Alaska.

BACKGROUND: Severe physical and environmental stress seems to have a suppressive effect on the hypothalamic-pituitary-gonadal (HPG) axis in men. Examining hormonal responses to an extreme 160-km competition across frozen Alaska provides a unique opportunity to study this intense stress. OBJECTIVE: To examine hormonal responses to an ultra-endurance race. METHODS: Blood samples were obtained from 16 men before and after racing and analyzed for testosterone, interleukin-6 (IL-6), growth hormone (GH) and cortisol. Six subjects (mean (SD) age 42 (7) years; body mass 78.9 (7.1) kg; height 1.78 (0.05) m raced by bicycle (cyclists) and 10 subjects (age 35 (9) years; body mass 77.9 (10.6) kg; height, 1.82 (0.05) m) raced by foot (runners). Mean (SD) finish times were 21.83 (6.27) and 33.98 (6.12) h, respectively. RESULTS: In cyclists there were significant (p< or =0.05) mean (SD) pre-race to post-race increases in cortisol (254.83 (135.26) to 535.99 (232.22) nmol/l), GH (0.12 (0.23) to 3.21 (3.33) microg/ml) and IL-6 (2.36 (0.42) to 10.15 (3.28) pg/ml), and a significant decrease in testosterone (13.81 (3.19) to 5.59 (3.74) nmol/l). Similarly, in runners there were significant pre-race to post-race increases in cortisol (142.09 (50.74) to 452.21 (163.40) ng/ml), GH (0.12 (0.23) to 3.21 (3.33) microg/ml) and IL-6 (2.42 (0.68) to 12.25 (1.78) pg/ml), and a significant decrease in testosterone (12.32 (4.47) to 6.96 (3.19) nmol/l). There were no significant differences in the hormonal levels between cyclists and runners (p>0.05). CONCLUSIONS: These data suggest a suppression of the hypopituitary-gonadal axis potentially mediated by amplification of adrenal stress responses to such an ultra-endurance race in environmentally stressful conditions.

Dietary intake, serum hormones, muscle mass and strength during strength training in 49 - 73-year-old men.

Effects of dietary intake on serum hormones, muscle cross-sectional area (CSA) and strength during strength training were studied in two groups of men: 1) strength training + nutritional counseling (n = 22, 59.1 +/- 6.1 yrs), and 2) strength training (n = 23, 58.5 +/- 7.1 yrs). Both groups performed strength training twice a week for 21 weeks. Counseling increased carbohydrate (p < 0.01) and fiber intake (p < 0.001) and polyunsaturated/saturated fat-ratio (p < 0.05) and decreased fat intake (p < 0.01). Muscle strength and CSA increased by 16 - 20 % and by 5.4 - 5.9 % in both groups (p < 0.001). Changes in protein content of diet correlated with the changes in the acute postexercise concentrations of total (r = 0.64, p < 0.01) and free testosterone (r = 0.54, p < 0.05) after training in the counseling group. Moreover, changes in the free testosterone responses to heavy-resistance exercise correlated with the increases in the muscle CSA (r = 0.52, p < 0.05) in the counseling group. Serum basal testosterone/sex hormone-binding globulin-ratios correlated with the body mass normalized energy (kJ/kg: r = 0.54, p < 0.001), protein (g/kg: r = 0.42, p < 0.01) and fat (g/kg: r = 0.51, p < 0.01) intake in all participants during the training. The data indicate that protein and fat intake may influence serum testosterone concentrations and that the changes in exercise-induced testosterone responses may contribute to muscle mass development during strength training.

Effects of strength training and reduced training on functional performance and metabolic health indicators in middle-aged men.

Changes in muscular fitness and metabolic health indicators were examined in 22 men (57.9 +/- 6.6 years, BMI 24.5 +/- 2.6 kg/m (2)) and 21 control men (58.2 +/- 6.1 years, BMI 25.4 +/- 2.8 kg/m (2)) during two consecutive 21-week periods: 1) whole body progressive strength training (ST: twice a week), and 2) continued reduced training (CRT: 3 ST sessions/2 weeks, n = 17 + 17). After the 21-week ST period, maximal strength of leg extensors increased in the ST group by 19.6 +/- 7.6 % vs. 2.8 +/- 4.4 % (p < 0.001) and also 10-m walking time and 10-step stair-climbing time shortened by - 17.2 +/- 7.6 % vs. 4.1 +/- 3.9 % (p < 0.01) and by - 8.2 +/- 6.8 % vs. - 3.0 +/- 6.8 % (p < 0.05) compared to the controls. Systolic blood pressure (BP) decreased in the ST group by - 4.4 +/- 6.7 % vs. 1.3 +/- 9.5 % (p < 0.05) compared to the controls after the ST period. Muscle strength as well as walking and stair-climbing times remained the same during the CRT. However, the changes in diastolic BP (- 8.9 +/- 8.7 % vs. - 1.0 +/- 6.6 %, p < 0.05) and fasting blood glucose concentrations (0.1 +/- 0.4 mmol/L vs. 0.3 +/- 0.4 mmol/L, p < 0.05) differed between the ST and control groups after the whole 42-week study period. Strength training has positive health effects in aging men by increasing maximal strength and functional performance and by decreasing resting blood pressure and high-intensity reduced strength training can maintain these health benefits.

Nutritional aspects of women strength athletes.

Strength training elicits sports related and health benefits for both men and women. Although sexual dimorphism is observed in exercise metabolism, there is little information outlining the specific nutritional needs of women strength athletes. Many women athletes restrict energy intake, specifically fat consumption, in order to modify body composition, but this nutritional practice is often counter-productive. Compared to men, women appear to be less reliant on glycogen during exercise and less responsive to carbohydrate mediated glycogen synthesis during recovery. Female strength athletes may require more protein than their sedentary and endurance training counterparts to attain positive nitrogen balance and promote protein synthesis. Therefore, women strength athletes should put less emphasis on a very high carbohydrate intake and more emphasis on quality protein and fat consumption in the context of energy balance to enhance adaptations to training and improve general health. Attention to timing of nutrient ingestion, macronutrient quality, and dietary supplementation (for example, creatine) are briefly discussed as important components of a nutritionally adequate and effective strength training diet for women.

Relationship between diet and serum anabolic hormone responses to heavy-resistance exercise in men.

Relationship between dietary intake and serum anabolic hormone concentrations of testosterone (T), free testosterone (FT), and growth hormone were examined at rest as well as after the heavy-resistance exercise (HRE) in 8 strength athletes (SA) and 10 physically active non-athletes (NA). In the first part of the study serum basal anabolic hormone concentrations and dietary intake were examined in the total group of subjects. In the second part of the study a subgroup of 5 SA and 5 NA performed the high volume and high intensity HRE. Dietary intake was registered by dietary diaries for 4 days preceding the loading day. Significant correlations were observed between serum basal T and fat (E%: r = 0.55, p < 0.05, g/kg: r = 0.65, p < 0.01) and protein intake (E%: r = - 0.77, p < 0.001, g/kg: r = - 0.68, p < 0.01) in the total group of subjects. However, when the two groups were examined separately the significant relationships between serum basal T and dietary fat and protein could be noticed in SA only (fat g/kg: SA r = 0.77, p < 0.05; in NA r = 0.44, n.s., protein g/kg: SA r = - 0.84, p < 0.05; in NA r = 0.27, n.s.). Both serum T and FT responses to HRE were correlated with fat (E%: r = 0.85, p < 0.01 and r = 0.73, p < 0.05, g/kg: r = 0.72, p < 0.05 and r = 0.77, p < 0.01) and protein (E%: r = - 0.81, p < 0.01 and r = - 0.69, p < 0.05, g/kg: r = - 0.86, p < 0.01 and r = - 0.65, p < 0.05). The results suggest the possible role of diet leading to alterations in serum T and FT during prolonged strength training, and that diets with insufficient fat and/or excessive protein may compromise the anabolic hormonal environment over a training program.

Influence of muscle strength and total work on exercise-induced plasma growth hormone isoforms in women.

The purpose of this investigation was to determine the influence of physical strength and the ability to do more total work on human growth hormone (GH) variants to a heavy resistance exercise protocol in untrained women. From a distribution of 100 healthy, untrained women, the strongest 10 women (S) and the weakest 10 women (W) were compared for GH responses pre- and post an acute heavy resistance exercise test (AHRET, 6 sets of 10 RM squats, 2 minutes rest between sets). Blood samples were obtained pre-exercise and immediately post-exercise and subsequently analysed in total as well as fractionated by Sephacryl S-100R column chromatography into three molecular weight size classes: fraction A: > 60 kD, fraction B: 30-60 kD, fraction C: < 30 kD. For each total sample as well as each fraction, immunoreactive GH was measured via the Nichols IRMA, while bioactive GH was measured via the hypox rat tibial line bioassay and Diagnostic Systems Laboratory's immunofunctional GH ELISA. No exercise-induced changes or differences between groups were observed in the tibial line bioassay. However, the S group displayed a significantly higher pre-exercise resting value in the total fraction than the W group. Conversely, the W group exhibited a significantly higher pre-exercise value in the smaller molecular weight fraction C. With regards to the immunofunctional and immunoreactive assays, the total fraction, fraction A, and fraction B demonstrated significant (P < or = 0.05) exercise-induced increases in both the S and W group despite no group differences. For the Nichols and immunofunctional assays significant exercise-induced changes were observed in the smaller molecular weight C fraction in the W group but not the S group. However, the S group displayed a significantly higher pre-exercise value in fraction C relative to the W group. These data demonstrate for the first time that differences exist in the GH molecular weight variants between strong and weak untrained women, with the lower molecular weight variants seemingly less responsive to greater amounts of exercise in stronger women, thus suggesting differential regulation of GH molecular weight variants during resistance exercise due to pre-existing physical parameters.

Strength, workload, anaerobic intensity and the immune response to resistance exercise in women.

AIM: The mechanism linking exercise intensity to the magnitude of the immune response is not completely understood. The purpose of this investigation was to determine whether the immune response to resistance exercise was associated with (1) changes in workload or (2) anaerobic exercise intensity. METHODS: Previously untrained women underwent 6 months of resistance training for lower and upper body (TOTAL, n = 34) or for upper body alone (UPPER, n = 30). Lymphocyte subsets [T (CD3+), CD4+, CD8+, NK and B], functional markers (CD45RA+ and CD45RO+), and mitogen (phytohemagglutinin-M, concanavalin A and pokeweed mitogen) and superantigen (staphylococcus a. cowans)-stimulated proliferation were measured from blood samples collected pre- and post-exercise for a squat resistance exercise consisting of six sets of 10 repetitions at 75% of one repetition maximum. This protocol was performed before (T0) and after 3 (T3) and 6 months (T6) of training. RESULTS: Lymphocyte recruitment to the circulation and proliferation following resistance exercise did not differ between training groups at any time, although the TOTAL group performed at a higher workload as training progressed. With respect to anaerobic intensity, exercise-induced increases in NK, CD4+, CD8+ and B lymphocyte concentrations were 42 (P = 0.07), 76 (P < 0.05), 72 (P < 0.05) and 242% (P < 0.01) greater in women in the highest compared with the lowest post-exercise lactate quartiles. Lymphocyte proliferation did not differ between lactate quartiles. CONCLUSIONS: Anaerobic intensity, rather than increased strength and workload, is associated with the number of lymphocytes recruited to the circulation, but not T and B cell proliferation responses.

Effects of an 8-week weight-loss program on cardiovascular disease risk factors and regional body composition.

OBJECTIVE: To determine the influence of weight loss on multiple cardiovascular disease (CVD) risk factors. DESIGN: Overweight women (n = 12; mean 44.2% fat) and men (n = 10; mean 30.7% fat) participated in an 8 week weight-loss program that included dietary, exercise, multi-vitamin/mineral supplementation, and behavior modification components. Measurement of total and regional body composition assessed using dual energy X-ray absorptiometry (DEXA), circumferences and blood sampling for total cholesterol, LDL cholesterol, HDL cholesterol, triacylglycerols, homocysteine, insulin and leptin were performed before and after the weight loss intervention. RESULTS: Subjects increased their physical activity and decreased their energy intake, resulting in a mean decrease in body mass of - 4.3 +/- 3.4 kg in women and -4.7 +/- 3.1 kg in men. Fat accounted for 88 and 58% of the decrease in body mass in men and women, respectively. Proportionally, men lost significantly more fat mass from the trunk region compared to women. Serum total and LDL cholesterol were significantly decreased in men (-11 and -14%, respectively) but not women (-3 and -3%, respectively) and there were no changes in HDL cholesterol and triacylglycerols. Serum leptin was significantly decreased (-36%) and highly correlated to fat mass (r= 0.839). There were no changes in serum insulin and plasma homocysteine. CONCLUSIONS: These data indicate that short-term weight loss resulting from reducing percentage energy from fat, increasing physical activity and vitamin/mineral supplements including folic acid has a favorable effect on regional body composition and total and LDL cholesterol with minimal effects on HDL cholesterol, triacylglycerols, homocysteine and insulin and the effects are greater in men compared to women. Supplementation with folic acid or emphasis on folic acid-rich foods may be an important component of a weight loss program to prevent increases in homocysteine.

Safety measures of L-carnitine L-tartrate supplementation in healthy men.

The purpose of this investigation was to examine the effects of ingestion of L-CARNIPURE (L-carnitine L-tartrate [LCLT]) on alterations in a complete blood cell profile and in circulating metabolic enzymes. Using a balanced, placebo (P), cross-over design (1 week washout), 10 healthy, active men volunteered and acted as their own control taking either a P or LCLT supplement (3 g.day(-1)) for 3 weeks. Postabsorptive morning blood samples were obtained both before and after 21 days of P and LCLT supplementation. Serum samples were analyzed for clinical chemistries including a complete chemistry panel with markers of liver and renal function along with various minerals and electrolytes. In addition, whole blood was analyzed for a complete blood count with differential. It was determined that there were no statistically significant differences between the LCLT and the placebo conditions for any of the variables examined. The results of this study suggest that LCLT, when used as a dietary supplement, has no adverse effects on metabolic and hematological safety variables in normally healthy men.

American College of Sports Medicine position stand. Appropriate intervention strategies for weight loss and prevention of weight regain for adults.

In excess of 55% of adults in the United States are classified as either overweight (body mass index = 25-29.9 kg.m(-2)) or obese (body mass index > or = 30 kg.m(-2)). To address this significant public health problem, the American College of Sports Medicine recommends that the combination of reductions in energy intake and increases in energy expenditure, through structured exercise and other forms of physical activity, be a component of weight loss intervention programs. An energy deficit of 500-1000 kcal.d-1 achieved through reductions in total energy intake is recommended. Moreover, it appears that reducing dietary fat intake to <30% of total energy intake may facilitate weight loss by reducing total energy intake. Although there may be advantages to modifying protein and carbohydrate intake, the optimal doses of these macronutritents for weight loss have not been determined. Significant health benefits can be recognized with participation in a minimum of 150 min (2.5 h) of moderate intensity exercise per week, and overweight and obese adults should progressively increase to this initial exercise goal. However, there may be advantages to progressively increasing exercise to 200-300 min (3.3-5 h) of exercise per week, as recent scientific evidence indicates that this level of exercise facilitates the long-term maintenance of weight loss. The addition of resistance exercise to a weight loss intervention will increase strength and function but may not attenuate the loss of fat-free mass typically observed with reductions in total energy intake and loss of body weight. When medically indicated, pharmacotherapy may be used for weight loss, but pharmacotherapy appears to be most effective when used in combination with modifications of both eating and exercise behaviors. The American College of Sports Medicine recommends that the strategies outlined in this position paper be incorporated into interventions targeting weight loss and the prevention of weight regain for adults.

Differential effects of exhaustive cycle ergometry on concentric and eccentric torque production.

The purpose of this study was to investigate the potential differences in peak isokinetic concentric end eccentric torque following low- and high-intensity cycle exercise fatigue protocols. Ten healthy, recreationally-active men were tested in a balanced, randomized testing sequence for peak eccentric and concentric isokinetic torque (60 degrees/sec) immediately before and after three experimental conditions each separated by 48 hours: 1) a bout of high intensity cycling consisting of a maximal 90-second sprint; 2) a bout of low-intensity cycling at 60 rpm equated for total work with the high-intensity protocol: and 3) no exercise (control bout). Blood was drawn from an antecubital vein and plasma lactate concentrations were determined immediately before and after each experimental bout. Post-exercise plasma lactate concentrations were 15.1 +/- 2.5 and 4.7 +/- 1.9 mmol l(-1), respectively, following the high- and low-intensity protocols. The high intensity exercise bout resulted in the only post-exercise decrease in concentric and eccentric isokinetic peak torque. The percent decline in maximal force production was significantly (P< 0.05) greater for concentric muscle actions compared to eccentric (29 vs 15%, respectively). In conclusion, a 90-second maximal cycling sprint results in a significant decline in maximal torque of both concentric and eccentric muscle actions with the greatest magnitude observed during concentric muscle actions.

Effects of a high-fat diet on postabsorptive and postprandial testosterone responses to a fat-rich meal.

Postprandial testosterone concentrations have been shown to significantly decrease after a fat-rich meal, which may be due to inhibition of testosterone production by chylomicrons. We examined the effects of a high-fat diet known to reduce postprandial chylomicrons on the testosterone response to a fat-rich meal. Total testosterone (TT), free testosterone (FT), cortisol, and insulin responses to a high-fat test meal containing 5.44 MJ (1,300 kcal, 11% carbohydrate, 3% protein, 86% fat) were determined before (week 0) and after (week 8) an 8-week high-fat diet (64% fat) in 11 healthy men. The high-fat diet resulted in significant reductions in postabsorptive and postprandial serum triacylglycerols (55% and 50%, respectively). There were no significant changes in postabsorptive serum TT, FT, and cortisol, but insulin concentrations were significantly (P < or = .05) lower at week 8 (-28%). There was a significant reduction 1 hour after the fat-rich meal for TT (-22%) and FT (-23%), which remained significantly below baseline for 8 hours. Postprandial TT and FT responses were not significantly different after the 8-week high-fat diet. Postprandial serum cortisol concentrations were significantly reduced 1 hour after the meal. There were no significant differences before and after the high-fat diet. Insulin was significantly increased at the 0-, 1-, and 2-hour postprandial time points before and after the high-fat diet. Compared with week 0, insulin concentrations were significantly lower prior to and immediately after the fat-rich meal at week 8. These data indicate a fat-rich meal results in a prolonged reduction in TT and FT concentrations that is not altered by lowering postprandial chylomicrons. Alternative mechanisms (eg, higher uptake at the receptor level of cells) other than chylomicron-induced or insulin-induced inhibition of steroidogenesis are likely responsible for the reduction in TT and FT after a fat-rich meal.

Lymphocyte proliferation in response to acute heavy resistance exercise in women: influence of muscle strength and total work.

Little is understood about the immune responses to heavy resistance exercise. The purpose of this investigation was to determine the influence of physical strength and the ability to do more total work on lymphocyte proliferation after an acute bout of heavy resistance exercise. A group of 50 healthy but nonstrength trained women were recruited for the study and tested for their one repetition maximum (i.e. 1 RM or maximal mass lifted once). From the normal distribution of strength the top and bottom 8 women [mean age 22.5 (SD 3.1) years] were asked to volunteer to define our two groups (i.e. high strength and low strength). The two groups were significantly different (P < 0.05) in 1 RM squat strength [low strength 39.9 (SD 4.6) kg, 0.65 (SD 0.08) kg.kg body mass-1 and high strength 72.2 (SD 10.7) kg, 1.1 (SD 0.12) kg.kg body mass-1] but were not significantly different in body mass, age, activity levels, and menstrual status (all in same phase). Each performed a resistance exercise protocol consisting of six sets of 10 RM squats with 2 min rest between the sets. The 10 RM loads and total work were significantly greater in the high strength group than in the low strength group. Blood samples were obtained pre-exercise and immediately post-exercise for test for lactate (significant increase with exercise) and cortisol (no changes) concentrations with no differences noted between groups. Immunological assays on the blood samples determined the incorporation of tritiated thymidine by lymphocytes in responses to concanavalin A (ConA), phytohemagglutinin (PHA), and pokeweed mitogen (PWM). Following the squat exercise, there was a significant decrease in lymphocyte responsiveness to PWM in the high strength but not in the low strength group for both total proliferation and proliferation adjusted per B or T cell. On the other hand, lymphocytes from the low strength group proliferated to a significantly greater extent (adjusted per T cell) in response to ConA and PHA. These data indicate that the heavy resistance exercise protocol reduced the lymphocyte proliferative responses only in the stronger group of subjects. This effect may have been due to the high absolute total work and the greater exercise stress created by the resistance exercise protocol in the high strength group. Therefore, individuals performing at the same relative exercise intensity (i.e. 10 RM) in a resistance exercise protocol may have different immune responses stemming from differences in absolute total work performance.

Characteristics of circulating growth hormone in women after acute heavy resistance exercise.

The effects of exercise on the molecular nature of secreted human growth hormone (GH) or its biological activity are not well understood. Plasma from women (average age 23.6 yr, n = 35), drawn before and after an acute heavy resistance exercise test, was fractionated by size exclusion chromatography into three size classes, namely, > 60 kDa (fraction A), 30-60 kDa (fraction B), and < 30 kDa (fraction C), before GH assay. Concentrations of GH in these fractions, as well as in unfractioned plasma, were measured by the Nichols immunoradiometric assay, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) polyclonal competitive RIA, Diagnostic Systems Laboratory's immunofunctional assay (measures dimerization-capable species), and the rat tibial bioassay. Significantly increased circulating GH concentrations of two- to fourfold were observed when immunoassays in unfractionated plasma samples were used, but they showed no significant change with use of the rat tibial bioassay. Significant exercise-induced increases in GH were found in fractions B and C but not in fraction A. Because chemical reduction of the samples before GH immunoassay significantly increased GH concentrations in fractions B and C (Nichols and NIDDK kits) after exercise, it is concluded that exercise may specifically increase release of disulfide-linked hormone molecules and/or fragments. Finally, because most of the GH released after exercise was able to dimerize the GH receptor in vitro, it is also concluded that these forms have the two intact binding sites required to initiate signal transduction in target cells.

Physiological and performance responses to tournament wrestling.

PURPOSE: The purpose of this study was to investigate the physiological and performance responses to a simulated freestyle wrestling tournament after typical weight loss techniques used by amateur wrestlers. METHODS: Twelve Division I collegiate wrestlers (mean +/- SD;19.33 +/- 1.16 yr) lost 6% of total body weight during the week before a simulated, 2-d freestyle wrestling tournament. A battery of tests was performed at baseline and before and immediately after each individual match of the tournament. The test battery included assessment for body composition, reaction/movement time, lower and upper body power and isokinetic strength, and a venous blood sample. RESULTS: Lower body power and upper body isometric strength were significantly reduced as the tournament progressed (P < or = 0.05). Significant elevations in testosterone, cortisol, and lactate were observed after each match (P < or = 0.05). However, there was a significant reduction (P < or = 0.05) in resting testosterone values in the later matches. Norepinephrine increased significantly (P < or = 0.05) after each match, whereas epinephrine increased significantly (P < or = 0.05) after each match except the last match of each day. Plasma osmolality was consistently higher than normal values at all times including baseline, with significant increases observed after each match (P < or = 0.05). CONCLUSIONS: Tournament wrestling augments the physiological and performance decrements of weight loss and its impact is progressive over 2 d of competition. The combined effects of these stresses may ultimately be reflected in a wrestler's ability to maintain physical performance throughout a tournament.