Alterations in neuromuscular function and perceptual responses following acute eccentric cycling exercise

Previous investigators have reported velocity-dependent strength loss for single-joint actions following acute eccentric exercise. The extent to which velocity influences recovery of multi-joint function is not well documented. Our main purpose was to compare alterations in maximal cycling power produced across a range of pedaling rates following eccentric exercise. An additional purpose was to determine the extent to which changes in rating of perceived exertion (RPE) associated with submaximal cycling reflect changes in maximal cycling power. Eighteen cyclists performed baseline trials of maximal and submaximal single-leg concentric cycling immediately before and 24 and 48 h after acute submaximal single-leg eccentric (151 ± 32 W, 487 ± 107 s) and concentric (148 ± 21 W, 488 ± 79 s) cycling trials. Maximum cycling power (apex of power–pedaling rate relationship; P _max) was assessed using inertial-load cycling, and powers produced at 65, 110 and 155 rpm were also analyzed. Compared to baseline, P _max was reduced (11–13%) at 24–48 h in the eccentric leg (P < 0.001). Power produced at 65, 110 and 155 rpm was reduced by similar relative magnitudes (11–15%) at 24–48 h in the eccentric leg. RPE increased (15–18%) at 24–48 h in the eccentric leg (P < 0.001). Magnitudes of relative changes in RPE did not differ from those for P _max. There were no alterations in the concentric leg. Our results indicated a global, rather than velocity-specific, reduction in neuromuscular function. Such a global reduction does not support the notion of fiber-type specific damage from eccentric exercise. The similar relative changes in RPE and P _max suggest that increased exertion may reflect the need to recruit additional motor units to produce the same submaximal power.     

Reproducibility of the blood lactate threshold, 4 mmol·l<Superscript>–1</Superscript> marker,heart rate and ratings of perceived exertion during incremental treadmill exercise in humans

The aim of this study was to investigate the reproducibility of blood lactate measurements, heart rate (HR) and ratings of perceived exertion (RPE) during treadmill exercise at speeds corresponding to the lactate threshold (v _Th,la-) and a fixed blood lactate concentration of 4 mmol·l^–1(v _la-_,4). Possible differences in reproducibility related to fitness levels were also investigated. A group of 20 men [mean (SD)] [age 20.5 (1.4) years] and 16 women [age 21.2 (0.9) years] took part in the study. The subjects performed two identical incremental exercise tests consisting of at least six 4 min stages. Blood lactate concentrations, HR and RPE were recorded at the end of each stage. Limits of agreement (LoA), correlation coefficients and 95% confidence intervals for the mean difference between tests were employed to investigate the level of agreement and reproducibility of blood lactate concentration, HR and RPE. For the group as a whole, the sample correlation coefficient for speed at v _Th,la- was r=0.88, and was r=0.92 for the speed at v _la-_,4. At v _Th,la -, the correlation coefficients for the moderately fit and unfit were r=0.94 and r=0.36, respectively, and at v _la-_,4 r=0.93 and r=0.68, respectively. The LoA for the moderately fit group indicated that a change of 1.62 km·h^–1 in v _Th,la- would be necessary to be considered a change in training status. For HR and RPE, relationships between the tests were generally poor. The LoA suggested that changes in scores must be unacceptably large. These findings cast doubt on the sensitivity of testing for change of blood lactate concentration, HR and RPE in this population. Electronic Publication     

Effect of exercise-induced muscle damage on ventilatory and perceived exertion responses to moderate and severe intensity cycle exercise

This study examined the effect of exercise-induced muscle damage (EIMD) on ventilatory and perceived exertion responses to cycle exercise. Ten healthy, physically active men cycled for 6 min at moderate intensity and to exhaustion at severe intensity before and 48 h after eccentric exercise (100 squats with a load corresponding to 70% of body mass). Changes in ventilation and ratings of perceived exertion (RPE) were calculated for each individual and expressed against time (moderate and severe exercise) and as a percentage of time to exhaustion (severe exercise). Ventilation increased during moderate exercise at 48 h ( [(V)\dot]_\textE \dot{V}_{\text{E}} ; 34.5 ± 5.0 to 36.3 ± 3.8 l min⁻¹, P < 0.05) but increases in RPE were not significant. During severe exercise at 48 h, time to exhaustion (TTE) was reduced and [(V)\dot]_\textE \dot{V}_{\text{E}} (87.1 ± 14.1 to 93.8 ± 11.7 l min⁻¹) and RPE (15.5 ± 1.3 to 16.1 ± 1.4) were elevated (P < 0.05). When expressed as a percentage of TTE, the differences in ventilation and RPE values disappeared. Findings indicate that the augmented ventilatory response to cycle exercise following EIMD may be an important cue in informing effort perception during high-intensity exercise but not during moderate-intensity exercise.     

Impact of dehydration on a full body resistance exercise protocol

This study examined effects of dehydration on a full body resistance exercise workout. Ten males completed two trials: heat exposed (with 100% fluid replacement) (HE) and dehydration (~3% body mass loss with no fluid replacement) (DEHY) achieved via hot water bath (~39°C). Following HE and DEHY, participants performed three sets to failure (using predetermined 12 repetition maximum) of bench press, lat pull down, overhead press, barbell curl, triceps press, and leg press with a 2-min recovery between each set and 2 min between exercises. A paired t test showed total repetitions (all sets combined) were significantly lower for DEHY: (144.1 ± 26.6 repetitions) versus HE: (169.4 ± 29.1 repetitions). ANOVAs showed significantly lower repetitions (~1–2 repetitions on average) per exercise for DEHY versus HE (all exercises). Pre-set rate of perceived exertion (RPE) and pre-set heart rate (HR) were significantly higher [~0.6–1.1 units on average in triceps press, leg press, and approached significance in lat pull down (P = 0.14) and ~6–13 b min⁻¹ on average in bench press, lat pull down, triceps press, and approached significance for overhead press (P = 0.10)] in DEHY versus HE. Session RPE difference approached significance (DEHY: 8.6 ± 1.9, HE: 7.4 ± 2.3) (P = 0.12). Recovery HR was significantly higher for DEHY (116 ± 15 b min⁻¹) versus HE (105 ± 13 b min⁻¹). Dehydration (~3%) impaired resistance exercise performance, decreased repetitions, increased perceived exertion, and hindered HR recovery. Results highlight the importance of adequate hydration during full body resistance exercise sessions.     

Rating of perceived exertion during two different constant-load exercise intensities during arm cranking in paraplegic and able-bodied participants

This study assessed the relationship between rating of perceived exertion (RPE) and time to exhaustion during arm cranking exercise while exercising at two different constant-load exercise intensities in able-bodied and paraplegic individuals. The second aim of this study was to assess the rate of change in the RPE between the two different constant-load exercise intensities in absolute and relative terms. Ten able-bodied men and ten paraplegic men performed four exercise tests: (1) a ramp exercise test (started at 0 W and increased by 15 W min⁻¹), (2) a graded exercise test (GXT) (started at 30 W and increased by 15 W every 2 min); these tests were performed in counterbalanced order, (3) a constant-load exercise test equal to 50% delta [i.e., the difference between the gas exchange threshold and peak power output (Δ)], (4) a constant-load exercise test equal to 70% Δ; these tests were also performed in counterbalanced order. There was a strong linear relationship between the RPE and time to exhaustion (R ² ≥ 0.88) irrespective of exercise intensity and participants’ group. As expected, the rate of change in the RPE was significantly greater during 70% Δ compared to 50% Δ when the RPE was regressed against absolute time regardless of group. However, differences in the rate of change in the RPE were removed when the RPE was regressed against proportion of time, irrespective of group. These findings have important implications for predicting time to exhaustion while exercising at constant-load exercise intensity during arm cranking in able-bodied and paraplegic individuals.     

Effects of dietary leucine supplementation on exercise performance

Branched chain amino acids (BCAA), particularly leucine, have been suggested to be ergogenic for both endurance and strength/power performance. This study investigated the effects of dietary leucine supplementation on the exercise performance of outrigger canoeists. Thirteen (ten female, three male) competitive outrigger canoeists [aged 31.6 (2.2) year, VO_2max 47.1 (2.0) ml kg⁻¹ min⁻¹] underwent testing before and after 6-week supplementation with either capsulated L-leucine (45 mg kg⁻¹ d⁻¹; n=6) or placebo (cornflour; n=7). Testing included anthropometry, 10 s upper body power and work and a row to exhaustion at 70–75% maximal aerobic power where perceived exertion (RPE), heart rate (HR) and plasma BCAA and tryptophan concentrations were assessed. Leucine supplementation resulted in significant increases in plasma leucine and total BCAA concentrations. Upper body power and work significantly increased in both groups after supplementation but power was significantly greater after leucine supplementation compared to the placebo [6.7 (0.7) v. 6.0 (0.7) W kg⁻¹]. Rowing time significantly increased [77.6 (6.3)–88.3 (7.3) min] and average RPE significantly decreased [14.5 (1.5)–12.9 (1.4)] with leucine supplementation while these variables were unchanged with the placebo. Leucine supplementation had no effect on the plasma tryptophan to BCAA ratio, HR or anthropometric variables. Six weeks’ dietary leucine supplementation significantly improved endurance performance and upper body power in outrigger canoeists without significant change in the plasma ratio of tryptophan to BCAA.Parts of this work have previously been presented in abstract form: Crowe MJ, Weatherson JN (2002) The effects of dietary L-leucine supplementation on exercise performance. Sports Medicine and Science at the Extremes. Australian Conference of Science and Medicine in Sport. 12–16 October, Melbourne, Australia     

The effects of voluntary contraction intensity and gender on perceived exertion during isokinetic quadriceps exercise

The objectives of the present study were to: (1) examine perceived exertion across different target voluntary contraction intensities, (2) compare perceived exertion ratings with actual target intensities, and (3) compare perceived exertion ratings between males and females. The subjects for this study included 30 healthy, college-aged male (n=15) and female (n=15) volunteers. All subjects were free of orthopedic, cardiopulmonary, systemic and neurological disease. Each subject completed five maximal isokinetic, concentric quadriceps contractions in a seated position at 60° · s⁻¹ to determine their single, highest peak torque. All subjects then completed, in a random order, 3–5 submaximal isokinetic contractions at 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% of their single, highest peak torque. Each relative contraction level (i.e., percentage) was achieved by having the subjects attempt to match the peak of their torque curve to a horizontal line on a computer monitor. Perceived exertion was measured by asking the subjects to provide a number that corresponded to the feelings in their quadriceps during exercise by viewing a modified category-ratio (CR-10) scale. The results of a two-factor (gender × intensity) analysis of variance revealed a significant, intensity main effect (F _8,232=92.19, P < 0.001, η²=0.77, 1–β=0.99) and no significant gender main effect (F _8,232=2.66, P = 0.11, η²=0.09, 1–β=0.35) or interactions (F _8,232 = 1.01, P=0.43, η²=0.04, 1–β=0.46). The findings of this study demonstrate that perceived exertion is significantly (P < 0.05) different from the specific target values on the CR-10 scale at 10%, and 50–90% maximum voluntary contraction. The results revealed that the increase in perceived exertion across the contraction intensities could be fit to both linear (F _1,29=205.41, P < 0.001, η²=0.88, 1–β=0.99) and quadratic (F _1,29=10.05, P=0.004, η²=0.26, 1–β=0.87) trends. These findings suggest that perceived exertion is underestimated during submaximal isokinetic exercise, and is not different between males and females. Accepted: 18 October 2000     

Differentiated ratings of perceived exertion and various physiological responses during prolonged upper and lower body exercise

Summary This study examined whether prolonged exercise employing upper or lower body muscle groups led to significant alterations in three differentiated ratings of perceived exertion (RPE). Multiple regression analyses were used to identify those physiological responses which accounted for the greatest variability in these three RPE. Nine volunteer males performed 60 min of arm crank and cycle exercise at similar absolute and at similar relative exercise intensities. There were no significant differences (P>0.05) between arm and leg exercise for oxygen uptake ( ) during the absolute tests (~ 1.60 l·min^–1) or during the relative tests (~ 60% peak ). The RPE included local RPE (muscle and joint exertion), central RPE (ventilatory and circulatory exertion), and overall RPE. During the absolute tests, the final means for all three RPE were lower (P<0.05) for leg than arm exercise. No differences (P>0.05) were found during the relative tests between arm and leg exercise for any of the three RPE. Local RPE was generally higher than central RPE. The various physiological responses accounted for more (total) variance in all three RPE for arm than leg exercise (absolute and relative arm exercise: median R²=0.99; absolute and relative leg exercise: median R²=0.75). Lactate and the ventilatory equivalent of oxygen made the greatest contribution to R². These data suggest that RPE may be more closely related to relative exercise intensity, and perceptual cues may be more readily monitored from smaller muscle masses such as the upper body. Further, steady-state RPE was not attained during prolonged upper body exercise.     

Substrate utilization in boys during exercise with [13C]-glucose ingestion

The influence of glucose ingestion on substrate utilization during prolonged exercise in children and adolescents is currently unknown. In the present study we determined the effect of intermittent exogenous glucose (GLU_exo) ingestion on substrate utilization during prolonged exercise, in adolescent boys ages 13–17 years. Healthy untrained volunteers performed four 30-min exercise bouts on a cycle ergometer, separated by 5-min rest periods (≅60% maximum O₂ consumption), on two occasions spaced 1–4 weeks apart. Two trials were performed, a control trial (CT), in which subjects ingested water intermittently during the exercise, and a glucose trial (GT), in which subjects ingested a ¹³C-enriched GLU_exo drink (≅3 g glucose · kg body mass⁻¹), also intermittently during the exercise. Total free fatty acids (FAT_total), glucose (GLU_total) and carbohydrate (CHO_total) oxidation was determined from indirect calorimetry, while GLU_exo oxidation was calculated from the ¹³C/¹²C ratio in expired air after 5–10 min and 25–30 min of exercise in each bout. Heart rate and rating of perceived exertion (RPE) were determined at the same time intervals. The oxidation of CHO_total was 169.1 (12.9) g · 120 min⁻¹ and 203.1 (15.9) g · 120 min⁻¹ (P < 0.01) and that of FAT_total was 31.0 (4.2) g · 120 min⁻¹ and 17.1 (2.5) g · 120 min⁻¹ (P < 0.01) in CT and GT, respectively. GLU_exo oxidation in GT was 57.8 (4.3) g · 120 min⁻¹, or 34.2 (2.2)% of that ingested. Endogenous glucose oxidation was 169.1 (12.9) g · 120 min⁻¹ and 145.3 (11.9) g · 120 min⁻¹ (P < 0.01) in CT and GT, respectively. Insulin and glucose concentrations were higher in GT than in CT by 226% and 37%, respectively (both P < 0.05). Free fatty acids and glycerol concentrations were lower in GT than in CT, by 27% and 79%, respectively (both P < 0.05). Heart rate was similar between trials, but RPE was lower in GT vs CT at both 115 and 135 min. Thus, under these experimental conditions, GLU_exo intake spares endogenous carbohydrate and fat by 16% and 45%, respectively, contributes to approximately 25% of the total energy demand of exercise, and lowers the RPE. Accepted: 21 May 2000     

Perceived exertion and blood lactate concentration during graded treadmill running

The purpose of this study was to investigate the influences of treadmill gradients on the rating of perceived exertion (RPE) at two fixed blood lactate concentrations ( [La^–]_b). Ten subjects performed three different incremental treadmill protocols by running either uphill (concentrically-biased), downhill (eccentrically-biased), or on the flat (non-biased). Individual data of each protocol were interpolated to reflect [La^–]_b corresponding to 2.0 and 4.0 mmol·l^–1. At 2.0 mmol·l^–1 [La^– _b, RPE and treadmill speed during downhill running were greater than during level running which was greater than during uphill running (p < 0.05) . Also, the downhill heart rate (HR) was greater than the uphill HR, and downhill minute ventilation ( ) was greater than the level . Treadmill speed was the only measure at 4.0 mmol·l^–1 [La^–]_b to differ between gradients. There was a moderate correlation of RPE with HR at both [La^–]_b (r = 0.73 at 2.0 mmol·l^–1;r = 0.48 at 4.0 mmol·l^–1) while treadmill speed was moderately correlated with RPE only at 2.0 mmol·l^–1 [La^–]_b (r = 0.70). The results of this study demonstrated that the degree of eccentric-bias during running exercise is an influence of perceived exertion at a moderate but not at a high exercise intensity.     

The effect of selective beta1-blockade on EMG signal characteristics during progressive endurance exercise

This study analysed the effect of selective β₁-blockade on neuromuscular recruitment characteristics during progressive endurance exercise. Ten healthy subjects ingested a selective β₁-blocker, acebutolol (200 mg b.d.), for 7 days (for one of two cycling trials), with a 10-day wash-out period between trials. On the last day of acebutolol ingestion subjects performed three successive 15-min rides at 30%, 50% and 70% of their peak power output and then cycled at increasing (15 W min^–1) work rates to exhaustion. Force output, heart rate, submaximal V˙O₂, rate of perceived exertion (RPE), electromyographic (EMG) data and blood lactate were captured during the cycling activity. Peak work rate [270 (111) W vs 197 (75) W, CON vs BETA, P <0.01], time to exhaustion [49.7 (23.2) min vs 40.3 (23.7) min, CON vs BETA, P <0.05] and heart rate [mean, for the full ride 135.5 (38.3) beats min^–1 vs 111.5 (30.0) beats min^–1 CON vs BETA, P <0.05] were significantly lower for the group who ingested β₁-blockade (BETA) compared to the control group (CON). Although not significant, submaximal V˙O₂ was reduced in BETA during the ride, while RPE was significantly higher during the ride for BETA (P <0.01). Mean integrated electromyography was higher in the BETA group although these differences were not significant. Mean power frequency values of the BETA group showed a significant (P <0.05) shift to the upper end of the spectrum in comparison to the control group. Lactate values [11.7 (3.5) mmol.l^–1 vs 7.1 (4.1) mmol.l^–1 CON vs BETA] were significantly lower (P <0.05) at exhaustion in BETA. Significant reductions in cycling performance were found when subjects ingested β₁-blockers. This study has shown significant shifts to the upper end of the EMG frequency spectrum after β₁-blocker ingestion, which could be caused by a change in neuromuscular recruitment strategy to compensate for the impaired submaximal exercise performance. Electronic Publication     

Effects of acute carbohydrate supplementation during sessions of high-intensity intermittent exercise

Abs tract The present study evaluated the acute effects of carbohydrate supplementation on heart rate (HR), rate of perceived exertion (RPE), metabolic and hormonal responses during and after sessions of high-intensity intermittent running exercise. Fifteen endurance runners (26 ± 5 years, 64.5 ± 4.9 kg) performed two sessions of intermittent exercise under carbohydrate (CHO) and placebo (PLA) ingestion. The sessions consisted of 12 × 800 m separated by intervals of 1 min 30 s at a mean velocity corresponding to the previously performed 3-km time trial. Both the CHO and PLA sessions were concluded within ∼28 min. Blood glucose was significantly elevated in both sessions (123.9 ± 13.2 mg dl⁻¹ on CHO and 147.2 ± 16.3 mg dl⁻¹ on PLA) and mean blood lactate was significantly higher in the CHO (11.4 ± 4.9 mmol l⁻¹) than in the PLA condition (8.4 ± 5.1 mmol l⁻¹) (P < 0.05). The metabolic stress induced by the exercise model used was confirmed by the elevated HR (∼182 bpm) and RPE (∼18 on the 15-point Borg scale) for both conditions. No significant differences in plasma insulin, cortisol or free fatty acids were observed during exercise between the two trials. During the recovery period, free fatty acid and insulin concentrations were significantly lower in the CHO trial. Supplementation with CHO resulted in higher lactate associated with lipolytic suppression, but did not attenuate the cortisol, RPE or HR responses.     

Physiological responses during exercise to exhaustion at critical power

Critical power (CP) is a theoretical construct derived from a series of constant load tests to failure. Many studies have examined the methodological limitations of deriving CP, but few studies have examined the responses to exercise at CP in well-trained individuals. The purpose of the present study was to examine the physiological responses to exercise at CP. Seven male subjects [mean (SD) body mass 75.6 (6.4) kg, maximum oxygen uptake 4.6 (0.7) l min^–1] performed three constant load tests to derive CP. Subjects then exercised at CP until volitional exhaustion. Heart rate, oxygen consumption and blood lactate concentration were measured throughout. Repeated measures analysis of variance revealed significant differences over time in heart rate 118 (24) to 177(5) beats min^–1, oxygen consumption 3.7 (0.6) to 4.1 (0.5) l min^–1 and blood lactate concentration 4.3 (1.8) to 6.5 (2.0) mM. All seven subjects completed 20 min of exercise with the range of time to failure at CP from 20 min 1 s to 40 min 37 s. Time to failure and maximum oxygen consumption were significantly correlated (r=0.779, P<0.05). We conclude, therefore, that CP does not represent a sustainable steady-state intensity of exercise. Electronic Publication     

Can HRV be used to evaluate training load in constant load exercises?

The overload principle of training states that training load (TL) must be sufficient to threaten the homeostasis of cells, tissues, organs, and/or body. However, there is no “golden standard” for TL measurement. The aim of this study was to examine if any post-exercise heart rate variability (HRV) indices could be used to evaluate TL in exercises with different intensities and durations. Thirteen endurance-trained males (35 ± 5 year) performed MODE (moderate intensity, 3 km at 60% of the maximal velocity of the graded maximal test (vVO_2max)), HI (high intensity, 3 km at 85% vVO_2max), and PRO (prolonged, 14 km at 60% vVO_2max) exercises on a treadmill. HRV was analyzed with short-time Fourier-transform method during rest, exercise, and 15-min recovery. Rating of perceived exertion (RPE), blood lactate (BLa), and HFP₁₂₀ (mean of 0–120 s post-exercise) described TL of these exercises similarly, being different for HI (P < 0.05) and PRO (P < 0.05) when compared with MODE. RPE and BLa also correlated negatively with HFP₁₂₀ (r = −0.604, −0.401), LFP₁₂₀ (−0.634, −0.601), and TP₁₂₀ (−0.691, −0.569). HRV recovery dynamics were similar after each exercise, but the level of HRV was lower after HI than MODE. Increased intensity or duration of exercise decreased immediate HRV recovery, suggesting that post-exercise HRV may enable an objective evaluation of TL in field conditions. The first 2-min recovery seems to give enough information on HRV recovery for evaluating TL.     

Single and choice reaction time during prolonged exercise in trained subjects: influence of carbohydrate availability

The aim of the present study was to examine the effects of prolonged exercise at the ventilatory threshold and carbohydrate ingestion on single (SRT) and choice (CRT) reaction time. Eight well-trained triathletes completed three testing sessions within a 3-week period. Maximal oxygen uptake was determined in the first test, whereas the second and the third sessions were composed of a 100-min run (treadmill 15 min, overground 70 min, treadmill 15 min) performed at the velocity associated with the ventilatory threshold. During these submaximal tests, the subjects ingested (in random order) 8 ml·kg^–1 body weight of either a placebo (Pl) or 5.5% carbohydrate (CHO) solution prior to the first submaximal run and 2 ml·kg^–1 body weight every 15 min after that. The cognitive tasks were performed before and after exercise for CRT, and before, during each submaximal run and after exercise for SRT. Furthermore, at the end of each submaximal test subjects were asked to report their rating of perceived exertion (RPE). Results showed a significant positive effect of CHO ingestion on RPE and CRT performance at the end of exercise, while no effect of exercise duration was found in the Pl condition. After a 100-min run, during the CHO condition, CRT mean (SD) group values decreased from 688.5 (51) ms to 654 (63) ms, while during the Pl condition, RPE mean group values increased from 11 (2) to 16 (1.02) and CRT mean values remained stable [688 (104) ms vs 676 (73.4) ms, P>0.05]. No similar effect was observed for SRT. These results suggest that CHO-electrolyte ingestion during a100-min run results in an improvement in the complex cognitive performance measured at the end of that run. Electronic Publication     

Effect of air ionization on heart rate and perceived exertion during a bicycle exercise test

Summary The influence of ionization of air on heart rate (HR) and ratings of perceived exertion (RPE) during bicycle exercise was studied in nine healthy medical students selected according to a randomized schedule from the class of 90 students. The exercise tests were performed both under negative and positive ionization. The study was made with a double-blind, cross-over design. The body surface exposed to ionic current was made large by reducing the clothing of the subject. A significant overall tendency to lower HR and RPE values under negative ionization was observed (p<0.01, sign test). The RPE values were significantly lower (p<0.01, paired t-test and the Wilcoxon test) under negative than under positive ionization at the maximal work load level but not at other relative load levels. However, when separately tested at each relative load level HR values did not differ significantly in negative and positive ionization.The results of this pilot study indicate that ionic composition of the air can modify the RPE and possibly also HR during exercise; negative air ionization seems to be beneficial compared with positive ionization. The mechanisms involved are obscure, but we suggest that negative ionization of air may increase oxidative metabolism through generation of a superoxide radical (O₂ ^–) that is reduced to H₂O₂ by superoxide dismutases.     

Does the amount of exercising muscle alter the aerobic demand of dynamic exercise?

The primary purpose of this study was to determine if the aerobic demand for production of specified power outputs is altered by distribution of work between the arms and legs compared with when all the work is performed by the legs. Because of the important exercise training implications, a secondary purpose of this study was to determine if the exercising muscle mass affects the cardiorespiratory demands at specified rating of perceived exertion (RPE) levels and blood lactate concentrations. Nine healthy adults completed leg cycling and combined arm and leg exercise on an Airdyne using a discontinuous protocol. Repeated measures ANOVA revealed that oxygen uptake for the combined arm and leg exercise averaged 0.04 l·min⁻¹ greater (p<0.05) than for leg cycling at the same external power outputs. However, RPE levels at specified power outputs were lower (p<0.05) with combined arm and leg exercise than leg cycling. At specified RPE levels and blood lactate concentrations, oxygen uptake and heart rate values were higher (p<0.05) for combined arm and leg exercise than leg cycling. From these findings we conclude that: (1) the addition of arm exercise to leg cycling results in a reduction in RPE, but a minimal increase in oxygen consumption to perform a given power output, and (2) if training intensity is established by RPE or blood lactate concentration, use of a muscle mass larger than that used in leg cycling should allow a greater cardiorespiratory training effect.     

The relationship of plasma ammonia and lactate concentrations to perceived exertion in trained and untrained women

Summary The purpose of this study was to investigate the covariance between perceived exertion (recorded using Borg's category-ratio scale CR-10) and the relative oxygen uptake, and lactate and ammonia concentrations in blood from a peripheral vein. Ratings of perceived exertion (RPE) at 25%, 50%, 75% and 90% maximal oxygen uptake and lactate and ammonia concentrations were compared in well-trained women distance runners (n = 22) and untrained women (n = 10). Ammonia concentrations in peripheral venous blood were significantly correlated with RPE (P < 0.05), both in the trained and untrained women. Differences between the trained and untrained subjects occurred when the ammonia concentration increased to 148 mol · l^–1 in both groups investigated; similarly, the mean RPE correlated significantly with the lactate concentration (P < 0.05), both in the trained and untrained women and there was a difference in RPE between groups when lactate concentration in the blood had risen to 4.4 mmol · l^–1. It would seem that the correlation of blood ammonia and lactate concentrations with RPE during exercise could be a useful indicator of the development of fatigue.     

The effects of whole body vibration and exercise on fibrinolysis in men

Whole body vibration (WBV) is a novel modality that has been demonstrated to enhance muscular and cardiovascular functions reported to increase fibrinolytic activity. The purpose of this study was to examine the fibrinolytic response to WBV and exercise in men. Twenty healthy males (23.8 ± 0.9 years, 25.6 ± 0.2 kg m⁻²) participated in the study. Each subject performed three trials in randomized order separated by 1 week: exercise (X), vibration (V) and vibration + exercise (VX). Exercise sessions consisted of 15 min of unloaded squatting at a rate of 20 per minute. Vibration sessions were conducted on a WBV platform vibrating for 15 min. Tissue plasminogen activator (tPA) and plasminogen activator inhibitor (PAI-1) were assessed at baseline and immediately after each condition. The increase in tPA activity was significantly greater in VX (0.87 ± 0.35 to 3.21 ± 1.06 IU ml⁻¹) compared to X (0.71 ± 0.36 to 2.4 ± 1.13 IU ml⁻¹) or V (0.83 ± 0.25 to 1.00 ± 0.37 IU ml⁻¹) conditions, and greater in the X condition compared to the V condition. PAI-1 activity decreased significantly more in the VX (6.54 ± 5.53 to 4.89 ± 4.13 IU ml⁻¹) and X (9.76 ± 8.19 to 7.48 ± 7.11 IU ml⁻¹) conditions compared to the V (5.68 ± 3.53 to 5.84 ± 3.52 IU ml⁻¹) condition. WBV does not augment fibrinolytic activity in healthy men. However, WBV combined with squatting exercise increases fibrinolytic activity more than exercise alone.     

RPE-lactate dissociation during extended cycling

This study examined the association of blood lactate concentration [La] and heart rate (HR) with ratings of perceived exertion (RPE) during 60 min of steady workload cycling. Physically active college-aged subjects (n=14) completed an exhaustive cycling test to determine VO_{2 peak} and lactate threshold (2.5 mmol l^–1). Subjects then cycled for 60 min at the power output associated with 2.5 mmol l^–1 [LA]. HR, [LA], RPE-overall, RPE-legs and RPE-chest were recorded at 5, 10, 20, 30, 40, 50 and 60 min. The 60-min trials were below maximal lactate steady state, with peak lactate concentration occurring at 20 min after which [LA] declined. The 20-min point was therefore considered pivotal, and data at other points were compared to this time point. Repeated measures ANOVA with simple contrasts (alpha=0.05) showed (a) [LA] at 40, 50 and 60 min was significantly lower than at 20 min, (b) RPE-O and RPE-L were significantly greater at 30, 40, 50 and 60 min than at 20 min, (c) RPE-C was significantly greater at 40, 50 and 60 min than at 20 min, and (d) HR was significantly greater at 30, 40, 50 and 60 min than at 20 min. Significant (P<0.05) positive correlations were found between HR and RPE-O (r=0.43), RPE-L (r=0.48) and RPE-C (r=0.41) while correlations for [LA]-HR (r=0.13) and [LA]-RPE (RPE-O: r=–0.11, RPE-L: r=0.01, RPE-C: r=–0.06) were weak and non-significant. There is a dissociation of RPE and [LA] owing to RPE drift and lactate kinetics in longer duration sub-maximal exercise. Apparently, [LA] is not a strong RPE mediator during extended cycling.