Adaptations to a high-fat diet that increase exercise endurance in male rats

Eighty-seven male Sprague-Dawley rats (245-300 g) were randomly assigned to one of two experimental groups. The first group consumed a diet high in fat and low in carbohydrate (LCD), whereas the second group ate a normal diet (ND). After either 1 or 5 wk on the diets, rats from each group were killed either before or after an exhausting run on a rodent treadmill (35 m X min-1, 0% grade). The LCD animals ran significantly longer before exhaustion at both week 1 (44.9 +/- 5.1 vs. 41.6 +/- 4.2 min) and week 5 (47.1 +/- 3.6 vs. 35.5 +/- 3.1 min) (P less than 0.05). Adaptations to the LCD included lower muscle and liver glycogen content, decreased rate of glycogen breakdown during exercise, decreased lactate production, and elevated blood ketone levels. In addition to these substrate changes, the LCD caused increased enzyme activities of muscular 3-hydroxyacyl-CoA dehydrogenase (35-110%) and citrate synthase (15-20%). These data indicate that rats exposed to a high-fat diet are capable of prolonged intense exercise in spite of limited glycogen stores. This improved capacity for exercise appears to be partially the result of muscular adaptations to the diet, which apparently increase the ability to oxidize fat and concomitantly spare glycogen.     

Testosterone, endurance, and Darwinian fitness: natural and sexual selection on the physiological bases of alternative male behaviors in side-blotched lizards

The mechanistic bases of natural and sexual selection on physiological and behavioral traits were examined in male morphs of three colors of the side-blotched lizard, Uta stansburiana. Orange-throated males are aggressive and defend large territories with many females. Blue-throated males defend smaller territories with fewer females; however, blue-throated males assiduously mate guard females on their territory. Yellow-throated males do not defend a territory, but patrol a large home range. They obtain secretive copulations from females on the territories of dominant males. Males with bright orange throats had higher levels of plasma testosterone (T), endurance, activity, and home range size and concomitantly gained greater control over female home ranges than blue- or yellow-throated males. Experimentally elevating plasma T in yellow- and blue-throated males increased their endurance, activity, home range size, and control over female territories to levels that were seen in unmanipulated orange-throated males that had naturally high plasma T. However, the enhanced performance of orange-throated males is not without costs. Orange-throated males had low survival compared to the other morphs. Finally, some yellow-throated males transformed to a partial blue morphology late in the season and the endurance of these transforming yellow-throated males increased from early to late in the season. In addition, yellow-throated males that transformed to blue also had significantly higher plasma T late in the season compared to the plasma T earlier in the season. T appears to play an important role in the physiological changes that all three color morphs undergo during the process of maturation. In some yellow males, T plays an additional role in plastic changes in behavior and physiology late in the reproductive season. We discuss natural and sexual selection on physiological and behavioral traits that leads to the evolution of steroid regulation in the context of alternative male strategies.     

Effect of ginger extract ingestion on skeletal muscle glycogen contents and endurance exercise in male rats

[Purpose]Skeletal muscle glycogen is a determinant of endurance capacity for some athletes. Ginger is well known to possess nutritional effects, such as anti-diabetic effects. We hypothesized that ginger extract (GE) ingestion increases skeletal muscle glycogen by enhancing fat oxidation. Thus, we investigated the effect of GE ingestion on exercise capacity, skeletal muscle glycogen, and certain blood metabolites in exercised rats. [Methods]First, we evaluated the influence of GE ingestion on body weight and elevation of exercise performance in rats fed with different volumes of GE. Next, we measured the skeletal muscle glycogen content and free fatty acid (FFA) levels in GE-fed rats. Finally, we demonstrated that GE ingestion contributes to endurance capacity during intermittent exercise to exhaustion. [Results]We confirmed that GE ingestion increased exercise performance (p<0.05) and elevated the skeletal muscle glycogen content compared to the non-GE-fed (CE, control exercise) group before exercise (Soleus: p<0.01, Plantaris: p<0.01, Gastrocnemius: p<0.05). Blood FFA levels in the GE group were significantly higher than those in the CE group after exercise (p<0.05). Moreover, we demonstrated that exercise capacity was maintained in the CE group during intermittent exercise (p<0.05). [Conclusion]These findings indicate that GE ingestion increases skeletal muscle glycogen content and exercise performance through the upregulation of fat oxidation.     

Serum enzyme variations in men during an exhaustive "square-wave" endurance exercise test

The present study was designed to test if both the intensity and duration of the 45-min Square-Wave Endurance Exercise Test (SWEET) would produce changes in serum enzyme activities. Nine men, four sedentary (S) and five athletes (A), performed VO2 max and SWEET, at their Maximal Intensity of Endurance (MIE45) as defined by maximal heart rate and the impossibility of maintaining MIE 45 + 5% for 45 min. Arterial blood was sampled at rest (R), exercise (Ex) (45th min) and during recovery (15th min) for measurements of levels of Haemoglobin (Hb), Haematocrit (Hct), pH and seven serum enzymes: Creatine kinase (CPK), Hexose-phosphate isomerase (PHI), Aldolase (ALD), Lactate dehydrogenase (LDH), Malate dehydrogenase (MDH), Aspartate amino-transferase (ASAT or GOT), and Alanine aminotransferase (ALAT or GPT). Five enzymes increased significantly during exercise (MIE45), the delta % (Ex - R/R) increases were as follows: PHI (72%), MDH (28%), LDH (21%), CPK (17%), and GOT (13.5%), whilst only a 10% increase was observed for Hct and Hb and there was no significant change in the arterial pH. There was no correlation between the delta % of Hb, Hct, pH, and the results for the enzymes. Thus, it does not seem that haemoconcentration and arterial blood acidosis which occur during exercise are only at the origin of the observed increases in enzymes. A difference between "sedentary" and "athletes" subjects was found at rest and exercise (delta % = A - S/S) for CPK (R = 222%; Ex = 235%), GOT (R = 90%; Ex = 75%) and ALD (R = 99%; Ex = 54%). These results suggest that the MIE45, by measured increases in enzymatic activity, seems to require great muscular effort.     

Beta-endorphin and corticotropin release is dependent on a threshold intensity of running exercise in male endurance athletes

Relationship between the intensity of running exercise on a treadmill and the changes in the concentrations of beta-endorphin + beta-lipotropin (beta-E + beta-LPH) and adrenocorticotropic hormone (ACTH) in plasma were studied in 10 experienced male endurance athletes. At random order, the subjects run on a treadmill six exercises which required on an average (mean +/- S.E.) 50 +/- 0.8%, 58 +/- 0.8%, 69 +/- 1.1%, 80 +/- 0.7%, 92 +/- 1.0% and 98 +/- 0.5% of their maximal oxygen consumption. Plasma levels of beta-E + beta-LPH and ACTH did not show any significant changes during the 50-80%-tests. During the 92% test, the mean levels (+/- S.E.) of beta-E + beta-LPH and ACTH increased significantly (p less than 0.001), from 3.0 +/- 0.4 to 8.0 +/- 1.2 pmol/l and from 3.1 +/- 0.5 to 8.9 +/- 1.3 pmol/l, respectively, and during the 98% test, from 3.7 +/- 0.6 pmol/l to 20.4 +/- 1.5 pmol/l, and from 3.6 +/- 0.6 to 21.8 +/- 1.5 pmol/l, respectively. Increases in the plasma levels of beta-E + beta-LPH and ACTH were always accompanied by an increase in the blood lactate level. We conclude that intensive running with an anaerobic response causes an increase in the concentrations of beta-endorphin and ACTH in plasma in endurance athletes, whereas slight aerobic exercise did not elicit any response.     

Testosterone and reproductive effort in male primates

Considerable evidence suggests that the steroid hormone testosterone mediates major life-history trade-offs in vertebrates, promoting mating effort at the expense of parenting effort or survival. Observations from a range of wild primates support the “Challenge Hypothesis,” which posits that variation in male testosterone is more closely associated with aggressive mating competition than with reproductive physiology. In both seasonally and non-seasonally breeding species, males increase testosterone production primarily when competing for fecund females. In species where males compete to maintain long-term access to females, testosterone increases when males are threatened with losing access to females, rather than during mating periods. And when male status is linked to mating success, and dependent on aggression, high-ranking males normally maintain higher testosterone levels than subordinates, particularly when dominance hierarchies are unstable. Trade-offs between parenting effort and mating effort appear to be weak in most primates, because direct investment in the form of infant transport and provisioning is rare. Instead, infant protection is the primary form of paternal investment in the order. Testosterone does not inhibit this form of investment, which relies on male aggression. Testosterone has a wide range of effects in primates that plausibly function to support male competitive behavior. These include psychological effects related to dominance striving, analgesic effects, and effects on the development and maintenance of the armaments and adornments that males employ in mating competition.     

Substrate utilization during endurance exercise in men and women after endurance training

We investigated the effect of endurance training on whole body substrate, glucose, and glycerol utilization during 90 min of exercise at 60% peak O2 consumption (VO2(peak)) in males and females. Substrate oxidation was determined before and after 7 wk of endurance training on a cycle ergometer, with posttesting performed at the same absolute (ABS, W) and relative (REL, VO2(peak)) intensities. [6,6-2H]glucose and [1,1,2,3,3-2H]glycerol tracers were used to calculate the respective substrate tracee flux. Endurance training resulted in an increase in VO2(peak) for both males and females of 17 and 22%, respectively (P < 0.001). Females demonstrated a lower respiratory exchange ratio (RER) both pretraining and posttraining compared with males during exercise (P < 0.001). Glucose rate of appearance (R(a)) and rate of disappearance (R(d)) were not different between males and females. Glucose metabolic clearance rate (MCR) was lower at 75 and 90 min of exercise for females compared with males (P < 0.05). Glucose R(a) and R(d) were lower during exercise at both ABS and REL posttraining exercise intensities compared with pretraining (P < 0.001). Females had a higher exercise glycerol R(a) and R(d) compared with males both pre- and posttraining (P < 0.001). Glycerol R(a) was not different at either the ABS or REL posttraining exercise intensities compared with pretraining. We concluded that females oxidize proportionately more lipid and less carbohydrate during exercise compared with males both pre- and posttraining, which was cotemporal with a higher glycerol R(a) in females. Furthermore, endurance training resulted in a decrease in glucose flux at both ABS and REL exercise intensities after endurance exercise training.     

Comparison of caffeine and theophylline ingestion: exercise metabolism and endurance.

This two-part investigation compared the ergogenic and metabolic effects of theophylline and caffeine. Initially (part A), the ergogenic potential of theophylline on endurance exercise was investigated. Eight men cycled at 80% maximum O(2) consumption to exhaustion 90 min after ingesting either placebo (dextrose), caffeine (6 mg/kg; Caff), or theophylline (4.5 mg/kg Theolair; Theo). There was a significant increase in time to exhaustion in both the Caff (41.2+/-4.8 min) and Theo (37.4+/-5.0 min) trials compared with placebo (32.6+/-3.4 min) (P<0.05). In part B, the effects of Theo on muscle metabolism were investigated and compared with Caff. Seven men cycled for 45 min at 70% maximum O(2) consumption (identical treatment protocol as in part A). Neither methylxanthines (MX) affected muscle glycogen utilization (P>0.05). Only Caff increased plasma epinephrine (P<0.05), but both MX increased blood glycerol levels (P<0.05). Muscle cAMP was increased (P<0.05) by both MX at 15 min and remained elevated at 45 min with Theo. This demonstrates that both MX are ergogenic and that this can be independent of muscle glycogen.     

Testosterone control of male courtship in birds

A sequence of behaviours which we call courtship initiates reproduction in a large number of species. In vertebrates, as a component of male sexual behaviour courtship is strongly influenced by testicular androgen. Here I will review some salient issues about the regulation of courtship by testosterone in birds. The first section will briefly summarize the first 100 years of research on this topic. The specific role of testosterone or its oestrogenic metabolites in the control of different components of courtship will be the subject of the second section. Then, I will discuss how behavioural patterns can be recruited into courtship and modified in their structure by testosterone action. In the following section, the role of sexual selection and female choice in shaping the link between testosterone and courtship will be addressed. The problematic nature of the quantitative relationships between testosterone and behaviour will be topic of the fifth section. Finally, I will discuss how courtship traits that are activated by testosterone can be apparently independent of hormone blood concentrations. These issues will be examined in an evolutionary perspective, in an attempt to understand how natural and sexual selection have shaped the links between the hormone and the behaviour.     

Physostigmine: dose-response effects on endurance and thermoregulation during exercise.

We previously reported that the administration of 200 micrograms/kg of physostigmine (PH) to rats exercising on a treadmill resulted in decrements in both endurance (decreased running time to exhaustion) and thermoregulation. However, it was necessary to determine the dose-response effects of PH administration before PH-treated exercising rats could be used as a model with which to examine the relative anticholinergic potency of drugs. In the present work saline, 50, 100, or 200 micrograms/kg of physostigmine salicylate (0%, 40%, 50%, and 60% whole blood cholinesterase inhibition) was administered to rats (N = 12/group) prior to treadmill exercise (26 degrees C, 50% rh, 11 m/min, 6 degrees incline). The saline control group ran for 67 +/- 6 min (mean +/- SE) with a rate of rise of core temperature of 0.051 +/- 0.007 degrees C/min. The run times declined (80%, 64% and 48% of control) as rate of rise of core temperature increased (116%, 180%, and 214% of control) in a dose-dependent manner (50, 100, 200 micrograms/kg PH). Cholinergic symptoms such as salivation, tremors, and defecation were also affected in a dose-dependent manner by PH administration. Since cholinergic symptoms, thermoregulatory effects, and endurance decrements all vary in a dose-dependent manner with physostigmine administration, the exercising rat represents a useful model for examining the relative potency of cholinergic therapies.     

Testosterone and chemosensory detection in male Syrian hamster

Gonadal steroids stimulate both sexual motivation and performance. However, steroid facilitation of appetitive sexual behavior is poorly understood. The present study determined if castration impairs chemosensory detection in male hamsters. Chemosensory cues are the principal sensory modality to initiate mating in this species. We compared LiCl-induced conditioned taste avoidance to female hamster vaginal secretion (FHVS) in gonad-intact and castrated males. Following overnight water deprivation, males received FHVS for 15 min, followed by LiCl (2 ml of 0.15 M) or saline ip. The next day, fluid consumption in a two-bottle choice test was recorded for 5.5 h. Pairings were repeated 4×. Initially, discrimination of FHVS from estrous females (10 or 100 μg/ml) was compared with plain water. Subsequently, we determined if males could distinguish FHVS from Syrian vs. Djungarian females or from estrous vs. anestrous females. When 100 μg/ml FHVS was paired with saline, all gonad-intact and 86% of castrated males preferred FHVS over water. However, when 100 μg/ml FHVS was paired with LiCl, the preference was reversed: 12.5% of intact males and 25% of castrates preferred FHVS (P < 0.05 vs. saline pairing). When exposed to 10 μg/ml FHVS, neither gonad-intact nor castrated males expressed conditioned taste avoidance, suggesting that 10 μg/ml FHVS is below the threshold for detection. Comparing discrimination of FHVS from Syrian and Djungarian females, only castrated males developed a significant conditioned taste avoidance to Syrian FHVS paired with LiCl. While 71% of castrated males preferred Syrian FHVS after saline pairing, only 12.5% of castrates preferred Syrian FHVS after pairing with LiCl (P < 0.05). In gonad-intact males, 57% preferred Syrian FHVS after saline pairing, while 14% preferred Syrian FHVS following LiCl pairing (P > 0.05). Neither gonad-intact nor castrated males successfully discriminated between FHVS from estrous and anestrous females. These data demonstrate that castrated males perform as well as gonad-intact males in a test of LiCl-induced conditioned taste avoidance. Therefore, it is unlikely that steroids enhance detection of sexually relevant chemosensory cues.     

Testosterone supplementation in subordinate, small male lizards: consequences for aggressiveness, color development, and parasite load

According to the immunocompetence hypothesis, testosterone stimulatesthe expression of male sexually selected traits while decreasingimmunocompetence. This proposed trade-off was studied by experimentalsupplementation of testosterone to small, subordinate, dull-coloredmale lizards, Psammodromus algirus. Experimental males showeda tendency to overlap their home range with fewer small malesthan did control males and tended to be more aggressive. However,control males were observed more frequently attending femalesthan experimental males. The area of patches of breeding coloration,the number of ticks, and the frequency of recoveries of testosterone-supplementedand control males did not differ significantly. The resultssuggest that small adult males with high levels of testosteronebehave more aggressively, which may be advantageous to securinga breeding territory in the next season. However, the hormonedid not apparently affect ornamentation or parasite load. Weargue that, whatever the mechanisms involved, blocking effectsof testosterone may be adaptive because being cryptic facilitatesa sneaking strategy, and low ectoparasite load may improve survival     

Norepinephrine response to exercise at the same relative intensity before and after endurance exercise training

It is welldocumented that endurance exercise training results in a bluntednorepinephrine (NE) response to exercise of a given absolute exerciseintensity. However, it is not clear what effect traininghas on the catecholamine response to exercise of the same relativeintensity because previous studies have provided conflicting results.The purpose of the present study was, therefore, to determine thecatecholamine response to exercise of the same relative exerciseintensity before and after endurance exercise training. Six women andthree men [age 28 ± 8 (SD) yr] performed 10 wk oftraining. Maximal O₂ uptake(O_{2 max}) wasdetermined during treadmill exercise. Fifteen-minute treadmill exercisebouts were performed at 60, 65, 70, 75, 80, and 85% ofO_{2 max} before andafter training.O_{2 max} was increasedby 20% (from 39.2 ± 7.7 to 46.9 ± 8.1 ml · kg¹ · min¹;P < 0.05) in response to training.Plasma NE concentrations were higher(P < 0.05) during exercise at thesame relative intensity after, compared with before, training at65-85% ofO_{2 max.}Differences between heart rates and plasma epinephrine concentrationsafter, compared with before, training were not statisticallysignificant. These results provide evidence that the NE response toexercise is dependent on the absolute as well as the relative intensity of the exercise.     

Upper body muscle strength and endurance in relation to peak exercise capacity during cycling in healthy sedentary male subjects

The aim of this study was to investigate the relation between upper body muscle strength and endurance, and exercise capacity during an incremental cycle exercise test in sedentary healthy male subjects before and after 6 months of combined supervised group training. Exercise capacity was measured as maximal oxygen consumption (VO?peak) and maximum work rate (WR(peak)). Muscle strength and endurance of the upper body were assessed by bench press and isometric measurement of trunk extensor and flexor maximum voluntary contraction (MVC) and trunk extensor and flexor endurance. Thirty-one subjects were studied before and after the training period. Bench press and trunk extensor MVC correlated to exercise capacity at baseline and after training. Training improved VO?peak and WR(peak). The correlation between trunk extensor MVC and exercise capacity improved after training. Upper body strength may affect exercise capacity by increasing the rider's ability to generate force on the handlebar that can be transmitted to the pedals. Resistance training of the arms, chest, and trunk may help improve cycling performance.     

Health education and exercise stimulation for older people: development and evaluation of the program "Healthy and Vital"

In order to promote health in people of 65 years and older, TNO Prevention and Health developed, evaluated, and implemented "Healthy & Vital" (also known as "Ageing Well and Healthily"). Healthy & Vital consists of six sessions of health education and low-intensity exercises. This paper reports on the theoretical basis of the intervention, the methods and results of a Randomised Controlled Trial (n = 50), and a Community Intervention Trial (in 8 municipalities, n = 448). A brief report is given of the implementation study. Healthy & Vital had a number of positive physiological effects, such as a decrease in blood pressure (effect size -0.55), the Body Mass Index (effect 0.62), and the level of blood glucose (1.00), especially in women and in elderly people who are less active physically. Participants' understanding of health and illness increased significantly (effect 0.78). Due to ceiling effects only a few effects on subjective general health were found, and they disappeared after 6 months. A positive effect on feelings of loneliness remained even after 6 months (p < 0.1). The most important effect of Healthy & Vital was the increase in physical activity, especially in the least active elderly (p < 0.001). Twenty-five per cent of the participants continued activities with More Exercise for Seniors, 28% were still considering this, and 19% continued at home with the exercises they had learnt. Currently, Healthy & Vital is being implemented nationally by the Local Policy for the Elderly Knowledge Centre (www.lokoud.nl).     

Testosterone,androstenedione and dihydrotestosterone: Effects on mating behavior of male rats

The relative effectiveness of testosterone, androstenedione, and dihydrotestosterone in maintaining mating behavior following castration of male rats was studied. In Experiment 1 testosterone, but not dihydrotestosterone, was found to maintain mating. In Experiment 2 testosterone and androstenedione were found to be equally effective in maintaining mating. Dihydrotestosterone failed to maintain mating and was no more effective than no treatment at all. Testosterone, androstenedione, and dihydrotestosterone significantly enhanced seminal vesicle and penis weight. In Experiment 3 castrated male rats were administered radiolabeled testosterone, androstenedione, or dihydrotestosterone. Radioactivity was found in hypothalamic and seminal vesicle samples indicating that these steroids can be accumulated by brain as well as peripheral androgen-sensitive tissues. It was concluded that the peripherally active steroid dihydrotestosterone probably plays no role in the maintenance of sexual behavior.     

Metabolic and exercise endurance effects of coffee and caffeine ingestion

Caffeine (Caf) ingestion increases plasmaepinephrine (Epi) and exercise endurance; these results are frequentlytransferred to coffee (Cof) consumption. We examined theimpact of ingestion of the same dose of Caf in Cof or in water. Ninehealthy, fit, young adults performed five trials after ingesting(double blind) either a capsule (Caf or placebo) with water or Cof(decaffeinated Cof, decaffeinated with Caf added, or regularCof). In all three Caf trials, the Caf dose was 4.45 mg/kgbody wt and the volume of liquid was 7.15 ml/kg. After 1 h of rest, thesubject ran at 85% of maximal O₂consumption until voluntary exhaustion (~32 min in the placebo anddecaffeinated Cof tests). In the three Caf trials, the plasma Caf andparaxanthine concentrations were very similar. After 1 h of rest, theplasma Epi was increased (P < 0.05)by Caf ingestion, but the increase was greater(P < 0.05) with Caf capsules thanwith Cof. During the exercise there were no differences in Epi amongthe three Caf trials, and the Epi values were all greater(P < 0.05) than in the othertests. Endurance was only increased(P < 0.05) in the Caf capsule trial; there were no differences among the other four tests. One cannot extrapolate the effects of Caf to Cof; there must be a component(s) ofCof that moderates the actions of Caf.