The acute effects of exercise duration on serum lipoprotein metabolism

The purpose of this study was to determine the effect of exercise duration on lipoprotein responses. Twenty two normolipidemic male volunteers, ages 19-31 yrs (X +/- SEM = 23.1 +/- 2.94) participated in the study. Each was novice a runner (training less than 5 mi/wk). Subjects were assessed for baseline lipid measures of high density lipoprotein (HDL-C), low density lipoprotein (LDL-C), total cholesterol (TC) and triglycerides (TG). They were then evaluated for VO2max and ventilatory threshold (VT). Later they were matched for VO2max and randomly assigned to one of three groups which exercised for 15, 30 or 45 min respectively at a VO2 20% below VT. Subjects were evaluated again for HDL-C, LDL-C, TC and TG from blood samples taken pre-exercise and immediately post-exercise, as well as 1, 24 and 48 hrs post-exercise. A 3 X 4 split plot ANOVA found no difference for any lipid measure during the baseline period. A 3 X 5 split-plot ANOVA (covarying for pre-exercise measures) and post-hoc comparisons of pre- and post-exercise lipid levels indicated no significant differences occurred for either TC, TG or LDL-C measures (p less than 0.05). With respect to HDL-C, the 30 min group had significantly lower HDL-C at the 24 hr measure than did 45 min group (46.41 +/- 1.70 vs 53.34 +/- 1.73 mg.dl-1 respectively). No other differences were found. These findings indicate exercise duration will have an effect on acute responses of lipoprotein following exercise of low intensity.     

Differential effects of exercise intensity on serum uric acid concentration

To investigate the effects of exercise intensity and short-term training on alterations in plasma uric acid, two series of experiments were performed using untrained male subjects. In series 1, 6 subjects (age 19 to 23 yr) cycled at 120% VO2max for 1 min followed by 4 min recovery until fatigue or until 24 repetitions had been completed. In series 2, 7 subjects (age 19 to 25 yr) cycled continuously at 65% VO2max for 2 h. In both experiments, short-term training was performed by repeating the exercise protocol for three consecutive days. In series 1, a progressive increase of 40% (P less than 0.05) was observed on day 1 in plasma uric acid concentration over the duration of the exercise. On day 2, pre-exercise values remained elevated over day 1 (mean +/- SD, 476 +/- 77 vs 352 +/- 30 mumol.l-1) and showed a further 23% increase (P less than 0.05) with exercise. Although resting uric acid concentrations on day 3 were elevated (P less than 0.05) over day 1, the exercise levels between day 1 and day 3 were not different (P greater than 0.05). In contrast, in series 2, prolonged sub-maximal exercise failed to stimulate increases in uric acid concentration either between days or within days. It is concluded that exercise intensity rather than total work output is a critical factor mediating increases in blood uric acid concentration. These results are consistent with the interpretation that uric acid formation may arise from purine nucleotide degradation and fast-twitch fiber utilization during conditions of high energy utilization.     

The effect of warm-up on responses to intense exercise.

The purpose of this study was to determine if prior physical activity (warm-up) affected physiological responses to intense exercise. Eight highly trained collegiate swimmers performed a paced 365.8-m (440 yds) intense swim (mean +/- SE, 94.4 +/- 3.3% VO2max) 5 min after the following warm-up conditions: trial N, no warm-up; trial S, an intensity-specific interval set (4 x 45.7 m with one-min rest intervals at the intense swim pace); trial M, a mild-intensity, long-duration swim (1371.6 m at 64.7 +/- 3.3% VO2max); and trial MS, a mild-intensity, long-duration swim (1188.7 m at the same pace as trial M) followed by the intensity-specific interval set (trial S). When comparing trial N with trials M and MS, stroke distance (m/stroke) was significantly (p less than 0.05) lower during the last 91.4 m of the intense, paced swim and 3-, 5-, 8- and 10-min recovery blood lactate levels and one-minute recovery heart rates were significantly elevated (p less than 0.05). There was no significant difference (p greater than 0.05) in stroke distance during the final 91.4 m of the intense swim between trials S and N. There were no significant differences for any variables between trials M and MS. These results suggest that a warm-up consisting of mild-intensity, long-duration exercise was beneficial compared to no warm-up and that intensity-specific exercise was not a vital component of warm-up. Although performance was not directly measured, these data demonstrate the benefit of warm-up.     

Renal responses to bicycle exercise in trained athletes: influence of exercise intensity

The effects of exercise on renal function were studied in 11 male bicyclists, using a bicycle ergometer. At a work intensity of 100/150 W, bicycle exercise for 1 h was associated with a significant increase in urine volume, endogenous creatinine clearance, and renal sodium and potassium excretion. In contrast, exercise of the same duration at a work intensity of 150/200 W produced no significant changes in the above variables. Exercise intensity seems to influence renal responses, presumably through a differential effect on renal blood flow.     

The acute effect of exercise intensity on free throws in young basketball players

Purpose

Free throws (FT) accuracy is a major determinant of performance in basketball game. However, the effect of exercise intensities on FT accuracy has not been well studied. The aim of the present study was to examine the effect of different exercise intensities on FT accuracy in young male basketball players.

Methods

For this aim, 22 basketball players (age 16.12 ± 1.16 years, body mass 76.4 ± 13.3 kg and height 186.4 ± 8.9 cm), classified into 2 age groups (younger 15.28 ± 0.48 years, n = 11; older 16.97 ± 1.00 years, n = 11). The participants performed 50 FT under five conditions (i.e. 10 FT per condition): after rest (A), after 3 min shuttle running with ~9 km h^?1 (B), ~9.5 km h^?1 (C), ~10 km h^?1 (D) and ~10.5 km h^?1 (E).

Results

The analysis of variance showed a main effect of exercise intensity on FT accuracy (p = 0.003, η ² = 0.585), heart rate (HR) (p < 0.001, η ² = 0.990) and rate of perceived exertion (RPE) (p < 0.001, η ² = 0.703): (a) FT accuracy in the C and D conditions was higher than the A condition (p ≤ 0.004); (b) all conditions differed for HR (p ≤ 0.047), the higher was the exercise intensity the higher was the HR, whereas no difference was revealed between D and E conditions; (c) the same trend as in the HR was observed in RPE (i.e. the higher the exercise intensity, the higher the RPE), too, where all conditions differed (p ≤ 0.047), except between C and D, and between D and E conditions.

Conclusions

There was a significant exercise intensity × age interaction for RPE (p = 0.011, η ² = 0.516), but not for FT accuracy (p = 0.336, η ² = 0.224) or HR (p = 0.128, η ² = 0.329). The findings of the present study showed that a minimum of exercise intensity was necessary to achieve peak FT performance and a shape of inverse U was suggested for the relationship between FT accuracy and exercise intensity.

     

The effect of exercise training on salivary immunoglobulin A and cortisol responses to maximal exercise.

The salivary immunoglobulin A (s-IgA) and cortisol responses to maximal exercise were examined in 24 adult males (X +/- SD; 22.1 +/- 3.0 yrs) before and after 10 weeks of run training. The subjects performed an incremental treadmill test to exhaustion and were randomly assigned to one of three groups: control (CON; n = 5), low intensity training (LO; n = 8), or high intensity training (HI; n = 11). Following the ten weeks of training, the subjects performed a second maximal treadmill test. Saliva samples were collected before, as well as immediately and 1 hr following each of the maximal treadmill tests and were analyzed for s-IgA and salivary cortisol. Maximal oxygen consumption (VO2max) increased significantly (p < 0.05) in the LO and HI groups but remained unchanged in the CON group. The s-IgA levels decreased significantly (p < 0.05) immediately post-exercise but returned to pre-exercise levels by one hour recovery. In addition, s-IgA and cortisol levels were not significantly (p > 0.05) correlated at any of the sampling times. These findings indicated that the s-IgA response to maximal exercise was unaffected by moderate (70% of VO2 max) to heavy (86% of VO2max) training (designed to develop cardiorespiratory fitness in healthy non-athletic adults) and independent of salivary cortisol.     

The effect of exercise intensity on chronic inflammation: A systematic review and meta-analysis

ObjectivesChronic inflammation is independently associated with the incidence and progression of chronic disease. Exercise has been found to reduce chronic inflammation, however the role of exercise intensity (work rate) is unknown. This review aimed to determine the pooled effect of higher- compared to lower-intensity aerobic and resistance exercise on chronic inflammation in adults.DesignSystematic review and meta-analysis.MethodsFive electronic databases were searched. Intervention trials that assessed the effect of ≥2 different exercise intensities on peripheral markers of chronic inflammation [c-reactive protein (CRP), interleukin (IL)-6, tumour necrosis factor (TNF)-α and IL-10] in adults were included. Random-effect meta-analyses were conducted to calculate the mean difference in change scores between groups [effect size (ES)]. Sub-group analyses were performed to explore the influence of age, chronic disease, body mass index and intervention duration on inflammation heterogeneity.ResultsOf 3952 studies identified, 27 were included. There were no significant effects of exercise intensity on IL-6 (ES=-0.039, 95%CI=-0.353–0.275; p = 0.806), TNF-α (ES = 0.296, 95%CI=-0.184–0.777; p = 0.227) and IL-10 (ES = 0.007, 95%CI=-0.904–0.919; p = 0.987). A significant pooled ES was observed for higher- versus lower-intensity exercise on CRP concentrations, in studies of middle-aged adults (ES=-0.412, 95%CI=-0.821– -0.004, p = 0.048) or interventions >9 weeks in duration (ES=-0.520, 95%CI=-0.882–-0.159, p = 0.005).ConclusionsExercise intensity did not influence chronic inflammatory response. However, sub-analyses suggest that higher-intensity training may be more efficacious than lower-intensity for middle-aged adults, or when longer duration interventions are implemented (>9 weeks), in the most commonly-reported analyte (CRP).     

Effect of training status and relative exercise intensity on physiological responses in men

PURPOSE: This study examined the effect of training status and relative exercise intensity on physiological responses to endurance exercise in humans. METHODS: Seven endurance trained (TR: peak oxygen uptake [VO2peak] = 65.8 +/- 2.4 mL x kg(-1) min(-1)) and six untrained (UT: VO2peak = 46.2 +/- 1.9 mL x kg(-1) x min(-1)) men cycled for 60 min, either at a work rate corresponding to approximately 70% VO2peak or approximately 95% lactate threshold (LT). RESULTS: The work rate and relative exercise intensity (i.e., % VO2peak) for UT 95% LT were lower (P < 0.01) than for all of the other trials. Although the work rate for UT 70% VO2peak was lower (P < 0.001) than for TR 70% VO2peak and TR 95% LT, average heart rate (HR) for the trial was higher (P < 0.01) throughout exercise in UT 70% VO2peak compared with all of the other trials. Plasma lactate and ammonia concentrations were greater (P < 0.01) during exercise in UT 70% VO2peak compared with all of the other trials. There was a tendency (P = 0.077) for plasma hypoxanthine to be greater at 60 min in UT 70% VO2peak compared with the other trials. At no time were any of the plasma metabolite concentrations different between the UT 95% LT, TR 95% LT and TR 70% VO2peak trials. CONCLUSIONS: These data demonstrate that HR and plasma markers of metabolic stress were greater in UT compared with TR when exercise was performed at 70% VO2peak but were similar during exercise at 95% LT.     

Feeling state responses to acute exercise of high and low intensity

The purpose of the present study was to examine the effects of exercise intensity on feeling states following two acute bouts of exercise (i.e., 50% and 80% of age-predicted maximal heart rate reserve: HRR) in highly fit and unfit females. It was hypothesized that highly fit females would have increased positive well-being and/or reduced psychological distress post-exercise (high intensity) compared to unfit females while both groups would experience similar feeling states following moderate intensity exercise. Twelve highly fit and 12 unfit females completed 3 conditions: attention control and fitness test, and two acute bouts of exercise (30 minutes on a bicycle ergometer) at 50% and 80% age-predicted HRR. Pre- and post-exercise feeling states were measured via the Subjective Experiences Exercise Scale (McAuley & Courneya, 1994). Analyses indicated a time x condition x fitness interaction F(2,21)=6.07, p<.01 (eta2 =.37) for psychological distress. Follow-up univariate analyses revealed no change in the 50% or control conditions, however, psychological distress significantly increased for the unfit participants F(1,11)=4.68,p<.05 (eta2 =.29) while there was no change for the highly fit participants F(1,11)=2.14,p>.05 (eta2 =.16) in the 80% intensity condition. No fitness differences emerged with respect to positive well-being or fatigue. Therefore, the present study's results substantiate the need to consider fitness level in dose-response studies, particularly ones which examine negative feeling states.     

The effect of an exercise ball on trunk muscle responses to rapid limb movement

The use of exercise balls as an aid to facilitate improvements in posture in patients with trunk weakness is widely advocated. However, mechanisms underlying any effect on postural mechanisms have received little attention. This study compared the increases in trunk EMG activity in response to limb movement when seated on an exercise ball or on a chair in 16 healthy, moderately active subjects. At the sound of an auditory cue, the subjects carried out either hip flexion or arm flexion (unilateral or bilateral), as fast as possible, whilst sitting on an exercise ball or a standard chair. The amplitude of EMG activity was recorded from selected trunk muscles (erector spinae, external obliques, internal obliques and rectus abdominis) and either an upper limb muscle (deltoid) or a lower limb muscle (rectus femoris). There were minimal differences in amplitudes of EMG activity in any of the trunk muscles between the conditions (ball or chair) following the upper limb movements. These results suggest that there is no benefit in simple arm flexion movements whilst seated on the exercise ball in comparison to a chair. The onset and amplitude of the rectus abdominis (RA) and external obliques (EO) were significantly different between conditions in the hip flexion protocol. However, they do suggest significant benefit in decreasing RA and EO muscle activity onsets and increasing amplitude in the hip flexion condition. These results may have implications for rehabilitation of those with trunk muscle deficits such as stroke.     

The intensity of exercise in deep-water running

The intensity of exercise during 30-min sessions of continuous deep-water running at a "hard" pace was determined by monitoring oxygen consumption (VO2), respiratory quotient (RQ), heart rate, perceived physical effort and perceived aches and pains in the legs in eight competitive runners, six of whom had not previously practised the technique. The intensity was compared with that of 30-min runs on a treadmill at hard and "normal" training paces and a 30-min outdoor run at normal training pace. VO2 during the last session of deep-water running (73% of maximum VO2) was not significantly different from that of the treadmill hard run (78%), but was significantly higher than that of the treadmill normal run (62%). Similar results were obtained for RQ, perceived effort and pain. In contrast, heart rates for deep-water running were similar to those of normal training and significantly less than those of the treadmill hard run. The disparity between VO2 and heart rate for deep-water running may reflect cooling or increased venous return caused by water immersion. It is concluded that deep-water running can be performed at a sufficient intensity for a sufficient period to make it an effective endurance training technique.     

Effects of exercise training on serum lipid and lipoprotein concentrations in women: a meta-analysis

It has been suggested that regular exercise produces favorable changes in serum lipid and lipoprotein-cholesterol concentrations. However, most of the subjects in this area of research have been men. Given the differences in lipid profiles between men and women, we wanted to determine if these same favorable changes took place in women. Of the 145 longitudinal studies available in this area, 27 met the criteria for inclusion in this analysis (i.e., an exercise training study that used women subjects and measured changes in lipid concentrations). Results show that exercise does favorably alter serum lipid profiles in women by reducing total cholesterol (194 to 190 mg.dl-1; P = 0.02), triglyceride (91 to 82 mg.dl-1; P = 0.01), and the ratio of total cholesterol to high-density lipoprotein-cholesterol (3.28 to 3.16; mg.dl-1; P = 0.03). However, a significant increase in high-density lipoprotein-cholesterol or decrease in low-density lipoprotein-cholesterol concentration was not observed. Results also show that changes in body weight during exercise are associated with changes in total cholesterol (r = 0.56; P = 0.01) and triglyceride (r = 0.42; P = 0.06) concentrations, indicating that greater body weight losses resulted in larger decreases in cholesterol and triglyceride concentrations. Further analysis indicates that those women most at risk for heart disease (elevated pre-exercise cholesterol concentrations) responded most favorably to exercise training. These results suggest that exercise training, especially for those at risk for heart diseases is beneficial to the lipid profile of women.     

The role of resistance exercise intensity on muscle fibre adaptations

Although many training variables contribute to the performance, cellular and molecular adaptations to resistance exercise, relative intensity (% 1 repetition maximum [%1RM]) appears to be an important factor. This review summarises and analyses data from numerous resistance exercise training studies that have monitored percentage fibre type, fibre type cross-sectional areas, percentage cross-sectional areas, and myosin heavy chain (MHC) isoform expression. In general, relative intensity appears to account for 18-35% of the variance for the hypertrophy response to resistance exercise. On the other hand, fibre type and MHC transitions were not related to the relative intensity used for training. When competitive lifters were compared, those typically utilising the heaviest loads (> or =90% 1RM), that is weightlifters and powerlifters, exhibited a preferential hypertrophy of type II fibres when compared with body builders who appear to equally hypertrophy both type I and type II fibres. These data suggest that maximal hypertrophy occurs with loads from 80-95% 1RM.