Effects of resistive training on lipoprotein-lipid profiles: a comparison to aerobic exercise training

A recent surge of cross-sectional and longitudinal studies dealing with resistive training and lipid profiles have produced conflicting results. The majority of cross-sectional studies demonstrate a reduced HDL cholesterol level or elevated total cholesterol to HDL ratio in strength trained athletes as compared with endurance trained athletes. Because of selection biases from many of these studies, there is a lack of control for factors that may influence lipids and lipoproteins, such as age, body composition, diet, and anabolic-androgenic steroid use. Most investigators have reported improved lipoprotein-lipid profiles from resistive training programs. However, many of these studies have design flaws or limitations that make their conclusions questionable. The most serious design flaws include the combination of no control group and only one blood sample taken before and after training, the use of subjects who have low risk profiles, and the lack of control for dietary effects. In a recent study in which we attempted to control for these factors, no changes in lipid profiles were observed after 20 wk of resistive training among individuals at risk for coronary heart disease (CHD). A group serving as reference controls who participated in aerobic-type exercise training during the same time period reduced their plasma triglyceride levels but did not alter their cholesterol or lipoprotein levels. No changes in any lipids or lipoproteins were observed in a group of inactive controls. Thus, resistive training does not appear to alter lipoprotein-lipid profiles among individuals at risk for CHD.     

Effects of high- and low-intensity exercise training on aerobic capacity and blood lipids

Sixteen non-obese, non-smoking males, ages 20-30 yr, were assigned to one of two training groups, exercising on a cycle ergometer 3 d/wk for 18 wk: high-intensity (H; N = 7; 80-85% Vo2max, 25 min/session) or low-intensity (L; N = 9; 45% VO2max, 50/min/session). Data were obtained at 3-wk intervals for Vo2max, body weight, percent body fat, and 12-h fasting blood levels of cholesterol (CHOL), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C). The average post-training increase in VO2max for group H (0.56 l X min-1, 8.5 ml X min-1 X kg-1) was not significantly (P greater than 0.05) greater than for group L (0.45 l X min-1, 6.5 ml X min-1 X kg-1). Significant reductions in percent body fat occurred in both groups, amounting to an average fat loss of approximately 1.35 kg. No statistically significant changes in CHOL, TG, HDL-C, LDL-C, CHOL/HDL-C, or HDL-C/LDL-C occurred in either group. However, changes in HDL-C after 18 wk of training were inversely correlated (r = -0.57, P less than 0.05) with pre-training levels. We conclude that 1) the minimum exercise training-intensity threshold for improving aerobic capacity is at least 45% Vo2max; 2) 18 wk of high- or low-intensity exercise training is ineffective in significantly altering CHOL, TG, HDL-C, LDL-C, CHOL/HDL-C, and HDL-C/LDL-C in young male subjects with low blood lipid levels, and 3) exercise training-induced changes in HDL-C are dependent upon initial pre-training levels.     

The effect of detraining and reduced training on the physiological adaptations to aerobic exercise training

In previously sedentary individuals, regularly performed aerobic exercise results in significant improvements in exercise capacity. The development of peak exercise performance, as typified by competitive endurance athletes, is dependent upon several months to years of aerobic training. The physiological adaptations associated with these improvements in both maximal exercise performance, as reflected by increases in maximal oxygen uptake (VO2max), and submaximal exercise endurance include increases in both cardiovascular function and skeletal muscle oxidative capacity. Despite prolonged periods of aerobic training, reductions in maximal and submaximal exercise performance occur within weeks after the cessation of training. These losses in exercise performance coincide with declines in cardiovascular function and muscle metabolic potential. Significant reductions in VO2max have been reported to occur within 2 to 4 weeks of detraining. This initial rapid decline in VO2max is likely related to a corresponding fall in maximal cardiac output which, in turn, appears to be mediated by a reduced stroke volume with little or no change in maximal heart rate. A loss in blood volume appears to, at least partially, account for the decline in stroke volume and VO2max during the initial weeks of detraining, although changes in cardiac hypertrophy, total haemoglobin content, skeletal muscle capillarisation and temperature regulation have been suggested as possible mediating factors. When detraining continues beyond 2 to 4 weeks, further declines in VO2max appear to be a function of corresponding reductions in maximal arterial-venous (mixed) oxygen difference. Whether reductions in oxygen delivery to and/or extraction by working muscle regulates this progressive decline is not readily apparent. Changes in maximal oxygen delivery may result from decreases in total haemoglobin content and/or maximal muscle blood flow and vascular conductance. The declines in skeletal muscle oxidative enzyme activity observed with detraining are not causally linked to changes in VO2max but appear to be functionally related to the accelerated carbohydrate oxidation and lactate production observed during exercise at a given intensity. Alternatively, reductions in submaximal exercise performance may be related to changes in the mean transit time of blood flow through the active muscle and/or the thermoregulatory response (i.e. degree of thermal strain) to exercise. In contrast to the responses observed with detraining, currently available research indicates that the adaptations to aerobic training may be retained for at least several months when training is maintained at a reduced level. Reductions of one- to two-thirds in training frequency and/or duration do not significantly alter VO2max or submaximal endurance time provided the intensity of each exercise session is maintained.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effects of long-term aerobic exercise on EPOC

This study sought to determine the influence of 16 months of progressive aerobic exercise on excess postexercise oxygen consumption (EPOC) and the extent EPOC contributed to weight management. Twenty-five overweight/obese women and 16 overweight/obese men participated in a 16-month exercise program (moderate-intensity treadmill walking) that progressed across the first 26 weeks to 5 days.wk(-1), 45 min.session(-1), and 75% HRR. Three-hour EPOC was measured at baseline, 9 months, and 16 months by indirect calorimetry in response to an exercise session (treadmill walking), in which energy expenditure (EE) was estimated from the participant's previous 10 exercise sessions. For women, EPOC was 7.5 +/- 4.9, 9.6 +/- 7.6, and 6.5 +/- 6.5 L at baseline, 9 months, and 16 months, respectively (p > 0.05). For men, EPOC increased from baseline (11.8 +/- 6.8 L) to 9 months (13.5 +/- 8.6 L) (p < 0.05) with no further increase at 16 months (13.5 +/- 11.0 L). Change in EPOC was correlated with change in EE at 9 months (r = 0.65; p < 0.05) and 16 months (r = 0.58; p < 0.05) for men but not women. Progressive long-term exercise significantly influenced EPOC in overweight/obese men but not women. Change in volume of exercise likely explained the increase in energy expenditure during EPOC in men. EPOC contributed modestly to EE compared to the exercise itself.     

Effects of acute aerobic exercise on high-molecular-weight adiponectin

INTRODUCTION: Few studies have reported the response of high-molecular-weight (HMW) adiponectin to acute aerobic exercise. PURPOSE: The purpose of this study was to investigate the influence of acute aerobic exercise on HMW adiponectin in healthy men. METHODS: Eight healthy men (age, 24.9 +/- 1.8 yr; BMI, 21.9 +/- 0.5 kg x m) participated in this study. They performed two trials. Trial 1 [exercise trial (EX)] consisted of 60-min stationary cycle exercise (50% peak oxygen uptake) followed by 30-min rest. Trial 2 [control trial (CON)] was 90-min rest. Blood samples were drawn to assess hormones (catecholamine and insulin), metabolites (free fatty acid [FFA], glycerol, and glucose), and total and HMW adiponectin concentration. RESULTS: There were significant trial x group interactions in serum FFA and glycerol concentrations (P < 0.05). Serum FFA and glycerol concentrations were higher in EX than in CON (P < 0.05). There were significant trial x group interactions in plasma insulin and glucose concentration (P < 0.05). Plasma insulin and glucose concentrations were lower in EX than in CON (P < 0.05). Total adiponectin, HMW adiponectin concentration, and the ratio of HMW to total adiponectin concentration, however, were unchanged during aerobic exercise and postexercise. Also, those changes did not differ between EX and CON. CONCLUSION: Our results indicate that total adiponectin and HMW adiponectin concentrations are not regulated by the change of hormones or metabolites during acute moderate-intensity aerobic exercise and postexercise in healthy young men.     

Effects of aerobic exercise training on 24 hr profile of heart rate variability in female athletes

BACKGROUND: The aim of this study was to investigate the effects of exercise training on autonomic regulation of heart rate under daily life conditions. METHODS: Twenty-six healthy female athletes (age 24.5 +/- 1.9 yrs) involved in regular physical activity were recruited during a period of yearly rest and randomly assigned to a five-week aerobic exercise training program (n = 13) or to a non-exercise control group (n = 13). MEASURES: Before and after the five-week training, all subjects underwent a bycicle ergometer stress test and a 24-hour dynamic ECG monitoring. Autonomic regulation of heart rate has been investigated by means of both time and frequency domain analyses of heart rate variability (HRV). Spectral analysis of R-R interval variability (autoregressive algorithm) provided markers of sympathetic (low frequency, LF, 0.10 Hz) and parasympathetic (high frequency, HF, 0.25 Hz) modulation of the sinus node. RESULTS: Trained subjects showed a reduced heart rate response to submaximal workload. Before training there was no significant difference between the two groups. After training resting heart rate did not significantly differ between trained and untrained subjects. No significant differences were observed in the different time domain indexes of heart rate variability. The day-night difference in SD and SDRR were significantly less in the trained as compared to the untrained group. Normalized LF and HF components did not significantly differ between trained and untrained subjects, during the awake period. The decrease in the LF and the increase in the HF component during nighttime were significantly less in the trained group. The LF/HF ratio was significantly decreased during the night in the untrained group whereas it was not significantly different from the awake state in the trained group. CONCLUSIONS: These findings of the relative night-time increase in LF and the decrease in the day-night difference in time domain indexes of heart rate variability suggest that, in young female athletes, exercise training is able to induce an increase in the sympathetic modulation of the sinus node which may coexist with signs of relatively reduced, or unaffected, vagal modulation.     

The effect of aerobic exercise training on the lipid-lipoprotein profile of children and adolescents

Longitudinal paediatric population studies have provided evidence that the risk factor theory may be extended to children and adolescents. These studies could assist in identifying individuals at increased coronary risk. Numerous studies have focused on the effects of regular exercise on the paediatric lipoprotein profile, a recognised primary risk factor, with equivocal results. Cross-sectional comparisons of dichotomised groups provide the strongest evidence of an exercise effect. 'Trained' or 'active' children and adolescents demonstrate 'favourable' levels of high density lipoprotein-cholesterol (HDL-C), triacylglycerol, total cholesterol (TC)/HDL-C and low density lipoprotein-cholesterol (LDL-C)/HDL-C, whilst TC is generally unaffected. The evidence regarding LDL-C in these studies is equivocal. A possible self-selection bias means that a cause-effect relationship between exercise and the lipoprotein profile cannot be readily established from this design. Correlational studies are difficult to interpret because of differences in participant characteristics, methods employed to assess peak oxygen uptake and habitual physical activity (HPA), and the statistical techniques used to analyse multivariate data. Directly measured cardiorespiratory fitness does not appear to be related to lipoprotein profiles in the children and adolescents studied to date, although there are data to the contrary. The relationship with HPA is more difficult to decipher. The evidence suggests that a 'favourable' lipoprotein profile may be related to higher levels of HPA, although differences in assessment methods preclude a definitive answer. While few prospective studies exist, the majority of these longitudinal investigations suggest that imposed regular exercise has little, if any, influence on the lipoprotein levels of children and adolescents. However, most prospective studies have several serious methodological design weaknesses, including low sample size, inadequate exercise training volume and a lack of control individuals. Recent studies have suggested that increases in HDL-C and reductions in LDL-C may be possible with regular exercise. The identification of a dose-response relationship between exercise training and the lipoprotein profile during the paediatric years remains elusive.     

Effect of aerobic exercise training on renal responses to sodium in hypertensives

INTRODUCTION: Aerobic exercise training has been shown to improve cardiovascular function and lower blood pressure (BP) in older adults. The exact mechanism(s) by which aerobic exercise training elicits these changes are unknown; however, it is possible that changes in renal hemodynamics may play a role. PURPOSE: The present study was undertaken to examine the effect of aerobic exercise training on renal hemodynamics in older hypertensive individuals. METHODS: Renal plasma flow (RPF) and glomerular filtration rate (GFR) were determined by plasma and urinary clearances of 131I-hippuran and 99mTc-DTPA after 8 d of low (20 mEq) and high (200 mEq) Na+ diets in 31 older (63 +/- 1 yr), hypertensive (152 +/- 2/88 +/- 1 mm Hg) individuals at baseline and following 6 months of aerobic exercise training (at 75% VO2max, three times a week, 40 min per session). RESULTS: Following 6 months of aerobic exercise training, a significant increase was seen in maximal aerobic capacity (VO2max: 18.3 +/- 0.7 vs 20.7 +/- 0.7 mL.kg.min(-1), P = 0.017) as well as a significant decrease in resting systolic (152 +/- 2 vs 145 +/- 2 mm Hg, P = 0.037) and mean arterial (109 +/- 1 vs 105 +/- 1 mm Hg, P = 0.021) BP. No significant (P < 0.05) effects were seen of aerobic exercise training on RPF (208.8 +/- 12.2 vs 197.1 +/- 13.1 mL.min(-1).1.73 m(-2)), GFR (68.9 +/- 3.6 vs 69.0 +/- 3.9 mL.min(-1).1.73 m(-2)), or filtration fraction (35.3 +/- 2.3 vs 37.1 +/- 2.4%) on the low Na+ diet or RPF (210.6 +/- 12.8 vs 212.1 +/- 11.7 mL.min(-1).1.73 m(-2)), GFR (72.9 +/- 4.1 vs 77.3 +/- 4.3 mL.min(-1).1.73 m(-2)), or filtration fraction (37.1 +/- 2.5 vs 37.7 +/- 3.0%) on the high Na+ diet. CONCLUSIONS: Our results suggest that changes in renal hemodynamics do not contribute to the reduction in resting BP in older hypertensive persons.     

Changes in urinary zinc and copper with strenuous physical exercise

BACKGROUND: Air rescue trainees in the Japan Air Self Defense Force participate in a curriculum that includes 24 wk of strenuous physical training. The trace minerals zinc and copper are directly involved in many physiologic processes that are altered by physical exercise of this sort. It has also been demonstrated that urinary excretion of catecholamines (adrenaline and noradrenaline) increases during both mental work and physical exercise. HYPOTHESIS: Air rescue trainees will exhibit changes in trace mineral excretion and catecholamine levels that vary with the type of training undertaken. METHODS: The levels of urinary zinc (Zn), copper (Cu), noradrenaline (NAd), and adrenaline (Ad) were determined in 11 air rescue trainees before and after daily training sessions for consecutive 3- or 4-d periods during four phases of the curriculum, as follows: control (Cont), classroom instruction without physical exercise; preliminary (Prelim), daily exercise sessions for increased physical strength; basic (Basic), a combination of lectures and demanding physical exercise; and simulated mountain rescue (Sim). RESULTS: The mean urinary concentrations of Zn and Cu increased significantly after sessions with physical exercise (Prelim, Basic, and Sim), but remained unchanged for Cont. The NAd levels also increased significantly after training with physical exercise. In contrast, Ad levels increased significantly after sessions in all phases, both with and without physical exercise. CONCLUSIONS: The urinary levels of Zn, Cu, NAd, and Ad rose with strenuous exertion, whereas only Ad responded to both physical and mental tasking.     

Effect of moderate intensity aerobic exercise training on electrophysiological and biochemical correlates of sleep

Background

Sleep disturbance (SD) is quite prevalent among collegiate students and is reflected upon various scales of measurements such as electrophysiological and biochemical. Despite its high prevalence and negative consequences, very few studies have focussed on the management of SD in collegiates. Aerobic exercise (AE) is associated with improvement in sleep and due to its extensive benefits, it has been now considered as an alternative management strategy for SD.

Aim

To investigate the effect of 12-week AE training on electrophysiological and biochemical correlates of sleep in collegiate students.

Methods

Twenty-eight collegiate students with Pittsburgh sleep quality index score?>?5 were randomly assigned into two groups: AE and control. Both the groups were taught basic sleep hygiene (SH) at the beginning of study. AE group, in addition to SH, received 12 weeks of moderate intensity AE training on treadmill. Pre- and post-intervention measures were performed at baseline and after 12 weeks. Sleep latency (SL), total sleep time, percentage of N1, N2, N3, NREM, REM and sleep efficiency (SE%) were calculated from over-night polysomnography (PSG). Concentration of serum melatonin and cortisol were also measured pre and post intervention.

Results

2?×?2 mixed ANOVA resulted in significant decrease and increase in N1% and N3%, respectively, after 12 weeks of AE. Serum cortisol also showed a significant decrease in its concentration post-intervention. Serum melatonin and other PSG variables did not show any difference with AE training.

Conclusion

AE training for 12 weeks improved sleep on electrophysiological and biochemical scales in SD collegiates.

Trial registration number and date

CTRI/2019/05/019154.

     

Effects of chromium supplementation on glycogen synthesis after high-intensity exercise

PURPOSE: Chromium enhances insulin signaling and insulin-mediated glucose uptake in cultured cells. We investigated the effect of chromium on glycogen synthesis and insulin signaling in humans. METHODS: Sixteen overweight men (BMI = 31.1 +/- 3.0 kg.m) were randomly assigned to supplement with 600 microg.d chromium as picolinate (Cr; N = 8) or a placebo (Pl; N = 8). After 4 wk of supplementation, subjects performed a supramaximal bout of cycling exercise to deplete muscle glycogen, which was followed by high-glycemic carbohydrate feedings for the next 24 h. Muscle biopsies were obtained at rest, immediately after exercise, and 2 and 24 h after exercise. RESULTS: Elevations in glucose and insulin during recovery were not different, but the lactate response was significantly higher in Cr. There was a significant depletion in glycogen immediately after exercise, an increase at 2 h, and a further increase above rest at 24 h (P < 0.05). The rate of glycogen synthesis during the 2 h after exercise was not different between groups (Cr: 25.8 +/- 8.0 and Pl: 17.1 +/- 4.7 mmol.kg.h). Glycogen synthase activity was significantly increased immediately after exercise in both groups. Muscle phosphatidylinositol 3-kinase (PI 3-kinase) activity decreased immediately after exercise and increased at 2 h (P < 0.05), with a trend for a lower PI 3-kinase response in Cr (P = 0.08). CONCLUSIONS: Chromium supplementation did not augment glycogen synthesis during recovery from high-intensity exercise and high-carbohydrate feeding, although there was a trend for lower PI 3-kinase activity.     

State anxiety responses to acute resistance training and step aerobic exercise across eight weeks of training

BACKGROUND: The purpose of this study was to contrast state anxiety responses to acute aerobic and resistance exercise across an 8-week period. METHODS: State anxiety (STAI-Y1) was assessed immediately prior to and 5 min following 50-min exercise sessions in 42 adults enrolled in introductory level resistance training or step aerobic exercise classes. Participants were instructed to maintain an intensity between 70-80% of their own maximum in both exercise conditions. State anxiety was assessed at weeks one, four and eight of 16-week courses. RESULTS: Repeated measures ANOVA revealed that state anxiety decreased (p<0.05) following both exercise conditions (step aerobics: 36.65 to 33.03; resistance training: 35.12 to 30.39). The magnitude of the reduction did not differ significantly between conditions, nor did it change from week one to week eight. Participants were grouped into high and low baseline state anxiety groups to determine the potential influence of baseline anxiety. Reductions (p<0.05) in state anxiety were observed for the high baseline groups (step aerobics: 49.7 to 40.4; resistance: 47.6 to 38.5), and following step aerobic exercise for the low baseline group (29.9 to 26.8). However, state anxiety did not decrease (29.6 to 29.5) following resistance exercise in the low baseline group. CONCLUSIONS: These results indicate state anxiety reductions occur following 50-min of aerobic exercise or weight training, and responses were not altered across 8-weeks of training. Similar state anxiety reductions were observed for each exercise mode in cases with elevated baseline state anxiety values, low baseline state anxiety levels were significantly reduced solely in the step aerobics condition.     

Effects of resistance, endurance, and concurrent exercise on training outcomes in men

The specificity of training principle predicts that combining resistance and endurance training (concurrent training) could interfere with the maximum development of strength and endurance capacity that results from either type of training alone. PURPOSE: To determine whether endurance and resistance training performed concurrently produces different performance and physiologic responses compared with each type of training alone. METHODS: Untrained male volunteers were randomly assigned to one of three groups: endurance training (ET, N = 12); resistance training (RT, N = 13); and concurrent training (CT, N = 16). The following measurements were made on all subjects before and after 12 wk of training: weight, percent body fat, peak oxygen consumption (VO(2peak)), isokinetic peak torque and average power produced during single-leg flexion and extension at 60 and 180 degrees.s, one-repetition maximum (1RM) leg press, 1RM bench press, vertical jump height, and calculated jump power. RESULTS: Weight and lean body mass (LBM) increased significantly in the RT and CT groups (P < 0.05). Percent body fat was significantly decreased in the ET and CT groups. VO(2peak) was significantly improved only in the ET group. Peak torque during flexion and extension at 180 degrees.s(-1) increased in the RT group. Improvements in 1RM leg press and bench press were significant in all groups, but were significantly greater in the RT and CT compared to the ET group. Jump power improved significantly only in the RT group, and no group showed a significant change in vertical jump height. CONCLUSIONS: Concurrent training performed by young, healthy men does not interfere with strength development, but may hinder development of maximal aerobic capacity.     

Effects of aerobic training on fat distribution in male subjects

To investigate the effects of aerobic training on adipose tissue morphology and fat distribution, several indicators of body fatness (percent body fat, seven subcutaneous skinfolds, fat cell weight) were assessed in 13 sedentary male subjects (SS) submitted to a 20-wk aerobic training program and in 20 male long-distance runners (LDR). The LDR subjects had a mean +/- SD VO2max of 65.9 +/- 6.5 ml . min-1 . kg-1 and averaged 120 km . wk-1. Training increased the VO2max values of the SS group significantly (pre: 41.9 +/- 7.0 vs post: 53.4 +/- 6.4 ml . kg-1 . min-1; P less than 0.001) and decreased significantly percent body fat (P less than 0.01), sum of skinfolds (P less than 0.01), and fat cell weight (P less than 0.05). Trunk skinfolds were more altered by training than extremity skinfolds, with reductions of 22 and 12.5%, respectively. Significant correlations were found between fat cell weight and percent body fat in SS before and after training (r = 0.75; P less than 0.01), while no significant relationship was noted in the LDR group. Moreover, using the sum of skinfolds divided by percent fat or by fat mass to reflect the proportion of subcutaneous fat to total fat, the LDR subjects exhibited less subcutaneous fat than the SS group (P less than 0.01) and training did not alter these ratios in the SS group. These results suggest that 20 wk of aerobic training can alter body fatness in men but that the induced fat loss does not seem to deplete preferentially subcutaneous fat.     

Effects of chronic intense exercise training on the leukocyte response to acute exercise.

Circulatory leukocytes vary significantly in response to acute bouts of exercise. However, little is known concerning the adaptability of this response to chronic intense exercise training. We investigated the circulating leukocytic response to acute exercise in trained athletes during a 28-day intense exercise training program. On day 0, 14, 28 and two days after cessation of the increased training, eight trained male athletes (VO2max greater than 60 ml.kg-1.min-1) were subjected to a 20-km bicycle ergometer time trial. Blood samples were drawn before (PRE, for resting baseline values) and five minutes after (POST, response to acute exercise) the time trial. Beginning on day 0, athletes were instructed to increase the duration of their training 50%. The intense exercise training, which lasted 28 days, was verified weekly. Acute bouts of exercise caused a significant increase (p less than 0.05) in circulating white blood cells, lymphocytes, polymorphonuclear neutrophils and monocytes. The baseline resting values and the magnitude of the response to the acute bouts of exercise in the above parameters were not different during the 28 days of chronic intense exercise training or 2 days after cessation of training as compared to the values observed on day 0. Similarly there was a significant increase (p less than 0.05) in cortisol levels in response to the acute bouts of exercise during the chronic intense exercise training, but the increases were not different from that observed under baseline conditions. These results lead to the conclusion that chronic intense exercise training does not alter the circulating leukocytic response to acute exercise.     

Early effects of short-term aerobic training. Physiological responses to graded exercise

AIM: The aim of this study was to find out how early the moderate training effects appear and to check the hypothesis that familiarization with exercise protocol may contribute to an early physiological responses to training in previously sedentary subjects. METHODS: Twelve male, sedentary volunteers (22.0+/-0.7 yrs) were submitted to 3 weeks of a bicycle ergometer training, consisting of 45 min of exercise (at 70% VO(2)max), 3-4 times a week. The subjects performed 4 incremental exercise tests until volitional exhaustion: 2 before training (C1 and C2), and then after 1 (T1) and 3 (T3) weeks of training. During exercise HR, VO(2), electrical activity (EMG) of rectus femoris, biceps femoris, soleus and trapezius muscles were recorded and blood samples were taken for blood lactate (LA) determination. RESULTS: Already after 1 week of training HR decreased (p<0.05) with a further decline after 3 weeks the training (p<0.01). Maximal work load after 3 weeks of training increased to 277+/-10.4 W vs 250+/-9.5 W (p<0.05), VO(2)max achieved higher values than in C1 and C2 tests (p<0.05) and LA and EMG thresholds were elevated (p<0.05). CONCLUSION: A decrease in the resting and submaximal heart rate is the earliest effect of increased physical activity. Familiarization to exercise protocol decreased EMG of biceps femoris and soleus muscles during exercise, but did not influence that of rectus femoris muscle the most engaged during cycling.     

Effects of sprint interval training on VO2max and aerobic exercise performance: A systematic review and meta‐analysis

Recently, several studies have examined whether low‐volume sprint interval training (SIT) may improve aerobic and metabolic function. The objective of this study was to systematically review the existing literature regarding the aerobic and metabolic effects of SIT in healthy sedentary or recreationally active adults. A systematic literature search was performed (Bibliotek.dk, SPORTDiscus, Embase, PEDro, SveMed+, and Pubmed). Meta‐analytical procedures were applied evaluating effects on maximal oxygen consumption (VO_2max). Nineteen unique studies [four randomized controlled trials (RCTs), nine matched‐controlled trials and six noncontrolled studies] were identified, evaluating SIT interventions lasting 2–8 weeks. Strong evidence support improvements of aerobic exercise performance and VO_2max following SIT. A meta‐analysis across 13 studies evaluating effects of SIT on VO_2max showed a weighted mean effects size of g = 0.63 95% CI (0.39; 0.87) and VO_2max increases of 4.2–13.4%. Solid evidence support peripheral adaptations known to increase the oxidative potential of the muscle following SIT, whereas evidence regarding central adaptations was limited and equivocal. Some evidence indicated changes in substrate oxidation at rest and during exercise as well as improved glycemic control and insulin sensitivity following SIT. In conclusion, strong evidence support improvement of aerobic exercise performance and VO_2max following SIT, which coincides with peripheral muscular adaptations. Future RCTs on long‐term SIT and underlying mechanisms are warranted.     

Effects of exercise training on the menstrual cycle: existence and mechanisms

This review evaluates the status of the evidence that exercise training affects the menstrual cycle beginning with evidence for the existence of delayed menarche, amenorrhea, and luteal suppression in athletes. A later age of menarche and a higher prevalence of amenorrhea and luteal suppression have been observed in athletes, but there is no experimental evidence that athletic training delays menarche, and alternative sociological and statistical explanations for delayed menarche have been offered. Cross-sectional studies of amenorrheic athletes have revealed abnormal reproductive hormone patterns, suggesting that the GnRH pulse generator in the hypothalamus is failing to initiate normal hypothalamic-pituitary-ovarian function. Longitudinal data show that the abrupt initiation of a high volume of aerobic training can disrupt the menstrual cycle in at least some women, but these women may be more susceptible to reproductive disruption than others, and some aspect of athletic training other than exercise (such as caloric deficiency) may be responsible for the observed disruption. Luteal suppression may be an intermediate condition between menstrual regularity and amenorrhea in athletes, or it may be the endpoint of a successful acclimation to exercise training. A potential endocrine mechanism of menstrual disruption in athletes involving the hypothalamic-pituitary-adrenal axis is discussed. Finally, promising future directions for research on this topic are described.