The effect of short-duration sprint interval exercise on plasma postprandial triacylglycerol levels in young men

Abstract

It is well established that regular exercise can reduce the risk of cardiovascular disease, although the most time-efficient exercise protocol to confer benefits has yet to be established. The aim of the current study was to determine the effects of short-duration sprint interval exercise on postprandial triacylglycerol. Fifteen healthy male participants completed two 2 day trials. On day 1, participants rested (control) or carried out twenty 6 s sprints, interspersed with 24 s recovery (sprint interval exercise – 14 min for total exercise session). On day 2, participants consumed a high-fat meal for breakfast with blood samples collected at baseline, 2 h and 4 h. Gas exchange was also measured at these time points. On day 2 of control and sprint interval exercise trials, there were no differences (P < 0.05) between trials in plasma glucose, triacylglycerol, insulin or respiratory exchange ratio (RER). The area under the curve for plasma triacylglycerol was 7.67 ± 2.37 mmol · l^–1.4 h^–1 in the control trial and 7.26 ± 2.49 mmol · l^–1.4 h^–1 in the sprint interval exercise trial. Although the sprint exercise protocol employed had no significant effect on postprandial triacylglycerol, there was a clear variability in responses that warrants further investigation.     

Assessment of Differing Definitions of Accelerometer Nonwear Time

Abstract

Twelve college and high school varsity male swimmers swam 200 yd. for time once a day for 16 days following the ingestion of a large meal (673 g). Each subject performed under rotating experimental conditions, which involved a post-meal rest interval of ½ hr., 1 hr., 2 hr., or no eating for at least 3 hr. before swimming. A nonsignificant F of .53 was obtained when the data were subjected to a single-factor with repeated measures analysis of variance.

It was concluded that swimming performance time was not affected by the time interval between eating and swimming. No stomach cramps were reported; most cases of stomach nausea occurred in the ½-hr. interval group, and scattered minor physical disturbances occurred under the other conditions.     

Blood Plasma Cholesterol Changes during a Physical Training Program

Abstract

Blood plasma cholesterol levels were followed in six experimental and six control subjects during a five-week training program (two-mile run for time, five days per week) and an eight-week detraining period. Plasma cholesterol levels were determined by the Duboff-Stevenson ultramicro method.

Plasma cholesterol levels were significantly reduced during the course of intensive training. A temporary rise in plasma cholesterol occurred during exercise, probably indicative of fat mobilization and ultimate utilization during physical exercise. Plasma cholesterol levels returned to pretraining levels within four weeks after training was stopped. The diurnal and weekly blood cholesterol variations were rather small, 2 percent and 2.7 percent, respectively.

The pathways by which exercise assists in the lowering of plasma cholesterol levels are discussed.     

Adipose tissue lipolytic inhibition enhances the glucoregulatory properties of exercise in type 2 diabetes patients

Aims: Exercise combined with adipose tissue lipolytic inhibition augments intramuscular lipid and glycogen use in type 2 diabetes patients. The present study investigates the impact of adipose tissue lipolytic inhibition during exercise on subsequent postprandial glycemic control in type 2 diabetes patients.

Methods: Fourteen male type 2 diabetes patients (age 65?±?2 years, HbA_1c 6.7?±?0.1% (50?±?2?mmol/mol)) participated in a double-blind placebo-controlled randomized cross-over study in which subjects performed endurance-type exercise after being administered 250?mg of a nicotinic acid analogue (acipimox; ACP) or a placebo (PLA). A control experiment was included in which no exercise was performed (CON).

Results: Sixty minutes of endurance-type exercise (at 45% W_peak) did not significantly lower circulating plasma glucose and insulin excursions in PLA when compared with CON (P?=?.300). Acipimox administration strongly reduced circulating plasma FFA concentrations during exercise (P?i.e. postprandial) in ACP when compared with either CON (P?=?.041 and P?=?.002, respectively) or PLA (P?=?.009 and P?=?.001, respectively).

Conclusions: Collectively, exercise with adipose tissue lipolytic inhibition reduces postprandial blood glucose and insulin excursions and, as such, further improves glycemic control in male type 2 diabetes patients.     

Spot Reducing in Overweight College Women: Its Influence on Fat Distribution as Determined by Photography

Abstract

The purpose of this study was to assess the role of exercise in reducing body weight in overweight college women and to compare the effect of two types of exercises, spot and generalized, on the physical contour of the overweight individual. The experimental program which included a uniform diet resulted in a slight but significant reduction of weight. Planimetric measurements of selected areas and linear transverse measures, obtained from preexercise and postexercise photographs, yielded evidence of reduction in body segments where fat accumulations had been most conspicuous, regardless of the type of exercise administered.     

Effect of Including Parents in a School-Based Exercise and Nutrition Program for Children

Abstract

The purpose of this study was to examine the effect of parental involvement in a school-based program about exercise and nutrition. One fifth grade and one sixth grade class were randomly assigned to each of the three different treatment conditions, a school-and-home condition (n = 45), a school-only condition (n = 43), and a control condition (n = 44). In the school-and-home condition, the children's parents were also asked to participate in nutritional and exercise activities at home as a family “home team.” A multivariate analysis of variance on change scores was completed on the following variables: height, weight, skinfold, sit-and-reach, sit-ups, mile run, exercise knowledge, saturated fat, cholesterol, percent calories from fat, percent calories from carbohydrates, and nutrition knowledge. There was a significant difference among groups. The school-and-home and school-only groups showed significantly greater improvement than the control group but were not significantly different from each other. Univariate analyses on posttest scores indicated that the school-and-home children scored significantly higher than the control group on sit-and-reach flexibility and nutrition knowledge. The results indicate that including the family was primarily effective in facilitating children's improvements in flexibility and nutrition knowledge rather than in diet and exercise behaviors.     

Reduced fat oxidation during high intensity,submaximal exercise: is the availability of carnitine important?

Abstract

The increased energy demand that occurs with incremental exercise intensity is met by increases in the oxidation of both endogenous fat and carbohydrate stores up to an intensity of ~70% V˙O_2max in trained individuals. However, when exercise intensity increases beyond this workload, fat oxidation rates decline, both from a relative and absolute perspective. As endogenous glycogen use is accelerated, glycogen stores can become depleted, ultimately resulting in fatigue and the inability to maintain high intensity, submaximal exercise (>70% V˙O_2max). Despite a considerable accumulation of knowledge that has been gained over the past half century, the precise mechanism(s) regulating muscle fuel selection and underpinning the aforementioned decline in fat oxidation remain largely unclear. A greater understanding would undoubtedly lead to novel strategies to increase fat utilization and, as such, improve exercise capacity. The present review primarily addresses one of the most prominent theories to explain the phenomenon of diminished fat oxidation during high intensity, submaximal exercise; a reduced availability of muscle free carnitine for mitochondrial fat translocation. This is discussed in the light of recent work in this area taking advantage of the discovery that muscle carnitine content can be increased in vivo in humans. Furthermore, the evidence supporting the recently proposed theory that reduced muscle co-enzyme A availability to several key enzymes in the fat oxidation pathway may also exert a degree of control over muscle fuel selection during exercise is also considered. Strong correlational evidence exists that muscle free carnitine availability is likely to be a key limiting factor to fat oxidation during high intensity, submaximal exercise. However, it is concluded that further intervention studies manipulating the muscle carnitine pool in humans are required to establish a direct causal role. In addition, it is concluded that while a depletion of muscle coenzyme A availability during exercise also offers a viable mechanism for impairing fat oxidation, at present, this remains speculative.     

Effects of interval aerobic training combined with strength exercise on body composition,glycaemic and lipid profile and aerobic capacity of obese rats

The purpose of this study was to investigate the effects of interval aerobic training combined with strength exercise in the same training session on body composition, and glycaemic and lipid profile in obese rats. Sixteen lean Zucker rats and sixteen obese Zucker rats were randomly divided into exercise and sedentary subgroups (4 groups, n = 8). Exercise consisted of interval aerobic training combined with strength exercise in the same training session. The animals trained 60 min/day, 5 days/week for 8 weeks. Body composition, lipid and glycaemic profiles and inflammatory markers were assessed.

Results showed that fat mass was reduced in both lean and obese rats following the exercise training (effect size (95% confidence interval (CI)) = 1.8 (0.5–3.0)). Plasma low-density lipoprotein–cholesterol and fasting glucose were lower in the exercise compared to the sedentary groups (d = 2.0 (0.7–3.2) and 1.8 (0.5–3.0), respectively). Plasma insulin was reduced in exercise compared to sedentary groups (d = 2.1 (0.8–3.4)). Some exercise × phenotype interactions showed that the highest decreases in insulin, homeostatic model assessment-insulin resistance, fasting and postprandial glucose were observed in the obese + exercise group (all, P < 0.01). The findings of this study suggest that interval aerobic training combined with strength exercise would improve body composition, and lipid and glycaemic profiles, especially in obese rats.     

Effects of Sit up Exercise Training on Adipose Cell Size and Adiposity

Abstract

The present experiment evaluated the effects of a 27-day sit up exercise training program on adipose cell size and adiposity. Fat biopsies were taken from the abdomen, subscapular, and gluteal sites by needle aspiration in 13 experimental and 6 control male subjects before and after a five days/week progressive training regimen. Day 1 consisted of 10 bouts of 10-sec exercise, 7 sit ups/bout, with 10-sec rest intervals; on day 27, 14 bouts of 30-sec exercise were performed, 24 sit ups/bout with 10-sec rest intervals. The total number of sit ups done was 5004. Fat cells were isolated using collagenase and photographed to determine cell diameter. Repeated measures ANOVA revealed significant decreases in cell diameter at the three biopsy sites (p<.01), but no significant differences in the rate of change (pre to post) in cell diameter between sites for the experimental and control groups (p>.05). Body weight, total body fat (underwater weighing), and fatfolds and girths remained unaltered. The results demonstrate that (1) the conventional sit up exercise does not preferentially reduce adipose cell size or subcutaneous fat thickness in the abdominal region to a greater extent compared to other adipose sites, and (2) significant changes in fat cell size may occur in the absence of changes in fatfolds, girths or total body composition.     

Correlates of Change in Walking for Exercise: An Exploratory Analysis

Abstract

This study was designed to identify correlates of change in walking for exercise. Respondents to a random sample mailed exercise survey were asked to complete a follow-up questionnaire 24 months after the first. Responses were obtained from 1,739 adults, reflecting an 86.6% return rate. Nonrespondents did not differ from respondents for baseline level of walking for exercise. Respondents overrepresented Caucasian and middle to high education (or income) adults. Residualized measures of change in walking for exercise served as the dependent variable, adjusted for baseline walking. Similarly, key independent variables, subject to change over time, were included after residualization. At both baseline and 24 months follow-up, adults walked for exercise an average of just under 1 hour per week, and 23.5% of the initially active adults ceased walking for exercise at 2 years. Multiple regression analyses explained more variance in walking for exercise among women than men. Change in dynamic variables such as friend's support and vigorous physical activity accounted for most of the explained variance. Results suggest that dynamic variables may need to be sustained to maintain walking for exercise. The limited explained variance suggests that more precise measures and additional determinants of walking for exercise need to be identified.     

Effects of Different Exercise Intensities With Isoenergetic Expenditures on C-Reactive Protein and Blood Lipid Levels

We investigated the effects of different exercise intensities on C-reactive protein (CRP), and whether changes in CRP levels correlated with blood lipid levels. Ten men exercised at 25%, 65%, and 85% of their maximum oxygen consumption rates. Participants' blood was analyzed for CRP and blood lipid levels before and after the exercise sessions. Although there was an intensity effect for postexercise high-density lipoprotein levels, there were no significant differences or correlations for postexercise CRP levels or between CRP and lipid levels across the three exercise intensities. In an acute aerobic bout model with isoenergetic expenditures, CRP was not affected by the exercise intensity. Additionally, changes in blood lipid levels might not have been connected to CRP levels for physically fit participants.     

Effect of the Menstrual Cycle on Pulse Rate and Blood Pressure before and after Exercise

Abstract

A random group of 24 college women was tested during four phases of the menstrual cycle to determine if the cycle had an effect on pulse rate and blood pressure before and after exercise. Analysis of variance data indicated that fluctuations in pulse rate and blood pressure before and after exercise could not be attributed to the menstrual cycle.     

Intensity of Treadmill Training and its Effect on Body Composition in Rats

Abstract

The purpose of this study was to determine which of three intensities of treadmill training produced changes in body composition in rats as evidenced by body weight, percentage of fat and specific gravity. Subjects were 60 male Wistar rats 25 to 30 days old when obtained. They were randomly assigned to one of five groups: sedentary controls, spontaneously active controls, and three groups of rats forced to exercise on a treadmill at intensities of 75, 125 and 175 fpm. Forced exercise was applied three times a week for 8 weeks, after which measures of body weight, specific gravity, and percentage of body fat were obtained. Results indicated that the sedentary controls had significantly higher mean body weights than did those which exercised. Rats forced to exercise at 75 fpm had significantly lower specific gravity measures than rats trained at 125 fpm. Sedentary controls had lower specific gravity values than did all rats allowed to exercise. Intensity of treadmill training had no effect on percentage of body fat as determined chemically. However, exercise was effective in reduction of body fat.     

Substrate oxidation during incremental arm and leg exercise in men and women matched for ventilatory threshold

Abstract

The aim of this study was to determine the variations in substrate utilization between men and women matched for ventilatory threshold (T _vent) during incremental arm cranking and leg cycling exercise at 70, 85, 100 and 115% of the mode-specific T _vent. Recreationally active men (n = 12) and women (n = 10) with similar values for percentage of peak oxygen consumption at T _vent participated in the study. Ventilatory equivalence, excess CO₂ and modified V-slope methods were used concurrently to determine T _vent. The participants performed 5 min of exercise at each of 70, 85, 100 and 115% T _vent during both arm cranking and leg cycling exercise. The females were tested during the early follicular phase for all trials. A two-way mixed-design analysis of variance was performed to test for differences between the sexes. When carbohydrate and fat oxidation were expressed relative to total fat-free mass, carbohydrate oxidation during arm cranking and leg cycling was significantly higher in men than women at each percentage of T _vent. In contrast, women showed significantly higher fat oxidation across intensities during both arm cranking and leg cycling. Our results suggest that when substrate utilization is expressed relative to total fat-free mass, women appear to maintain a higher rate of fat and lower rate of carbohydrate oxidation than men during both incremental arm cranking and leg cycling exercise relative to T _vent.     

Is the highest fat oxidation rate coincident with the anaerobic threshold in obese women and men?

Abstract

In this study we determined the exercise intensity that elicits the highest fat oxidation rate in 15 obese women and 13 obese men. Furthermore the relationship between this intensity with the lactate (LT) and ventilatory thresholds (VT) was investigated in order to give training recommendation for maximal fat utilization during endurance exercise. After an incremental exercise test until exhaustion on a cycle ergometer, subjects performed six 20-min exercise bouts of 25, 35, 45, 55, 65 and 75% VO₂peak. The 20 min stages were randomly assigned and spread over two separate occasions (three bouts per occasion). Substrate oxidation was measured with indirect calorimetry and was calculated using stochiometric equations. In both, women and men the highest fat oxidation rate occurred at 65% VO₂peak and this did not coincide with either the VT or LT. A significant correlation between VT and LT could not be found in women (r=0.33) nor men (r=0.277). In obese women and men training recommendation for maximal fat utilization should not only be given by the intensity at which AnT occurs.     

A short bout of high-intensity intermittent exercise before moderate-intensity prolonged exercise as a mean to potentiate fat oxidation ?

ABSTRACT

Moderate-intensity continuous exercise (MICE) improves fat oxidation. High-intensity intermittent exercise (HIIE) is thought to have a greater potential for fat oxidation but it might be too demanding in the long term for patients. We hypothesized that an initial bout of HIIE could maximize fat oxidation during MICE and the following passive recovery. Eighteen healthy participants performed two acute isocaloric exercise sessions at random. MICE consisted of 45-min cycling at 50% of maximal aerobic power (Pmax). COMB began with five 1-min bouts of HIIE at Pmax (interspaced with 1-min recovery periods) followed by 35-min MICE. Gas exchange allowed substrate oxidation rate assessment.

Expressed as a % of energy expenditure, fat oxidation (%) increased during in the passive recovery following COMB (Recovery: 36.0 ± 19.4 vs 23.0 ± 20.3%; ES: 0.66; p < 0.0001). An initial bout of HIIE preceding a prolonged moderate-intensity exercise may potentiate fat oxidation during the following recovery. This might be relevant for health management of overweight/obese persons.     

The 1983 C.H. McCloy Research Lecture Appetite and Body Composition Consequent to Physical Activity

Abstract

Body composition has become a major field of interest for many exercise and sport scientists as well as clinicians who specialize in the prevention of and rehabilitation from hypokinetic diseases. This review article discusses the state of the art within selected areas of body composition, including the following: exercise in appetite regulation, the use of body density to estimate relative body fat in selected populations, the use of anthropometric equations to estimate body composition, and alterations in body composition with exercise training. It was concluded that acute bouts of exercise may have short term anorexigenic effects, but that alterations in appetite with extended periods of training are less clearly defined. Exercise training does result in modest decreases in total and fat weight and in relative body fat, and small increases in lean body weight. However, these alterations are not substantial. Finally, major research efforts are needed to improve methodology in body composition assessment.     

Description of the Movement Characteristics of Two-Year-Old Children Performing the Jump and Reach

Abstract

The purpose of this study was to assess the effects of varied rest intervals, following a 5-min warm-up, upon subsequent ratings of perceived exertion, heart rate (HR), and state anxiety during an exercise period. The subjects were 16 male college students, each with predicted [Vdot]O₂ max of at least 51 ml/kg/min ( = 54.4) as determined by the Åstrand bicycle test. Each subject was tested under four experimental conditions following a 5-min warm-up on a bicycle ergometer at 75% of HR max. Rest intervals of 1 min, 5 min, 10 min, and no rest preceded a progressively increasing 8-min exercise period on a bicycle ergometer. Ratings of perceived exertion (RPE), heart rate, and state anxiety were obtained at 1,000, 1,200, 1,400, and 1,600 KPM during each of the experimental conditions. An analysis of variance, four by four factorial design with repeated measures on both factors, was used to determine if significant differences existed between the experimental conditions for RPE and HR. An analysis of variance, treatment by subjects design, was used to determine if there were significant differences in state anxiety levels among the experimental conditions. Intraclass correlations revealed that reliability for HR and RPE was extremely high. No significant difference was found among the four experimental conditions for perceived exertion, heart rate, and state anxiety. RPE was found to be a good predictor of physiological strain as indicated by HR.     

Considerations for protein intake in managing weight loss in athletes

Abstract

A large body of evidence now shows that higher protein intakes (2–3 times the protein Recommended Dietary Allowance (RDA) of 0.8 g/kg/d) during periods of energy restriction can enhance fat-free mass (FFM) preservation, particularly when combined with exercise. The mechanisms underpinning the FFM-sparing effect of higher protein diets remain to be fully elucidated but may relate to the maintenance of the anabolic sensitivity of skeletal muscle to protein ingestion. From a practical point of view, athletes aiming to reduce fat mass and preserve FFM should be advised to consume protein intakes in the range of ～1.8–2.7 g kg^?1 d^?1 (or ～2.3–3.1 g kg^?1 FFM) in combination with a moderate energy deficit (?500 kcal) and the performance of some form of resistance exercise. The target level of protein intake within this recommended range requires consideration of a number of case-specific factors including the athlete's body composition, habitual protein intake and broader nutrition goals. Athletes should focus on consuming high-quality protein sources, aiming to consume protein feedings evenly spaced throughout the day. Post-exercise consumption of 0.25–0.3 g protein meal^?1 from protein sources with high leucine content and rapid digestion kinetics (i.e. whey protein) is recommended to optimise exercise-induced muscle protein synthesis. When protein is consumed as part of a mixed macronutrient meal and/or before bed slightly higher protein doses may be optimal.