On the determination of ventilatory threshold and respiratory compensation point via respiratory frequency.

This study examined the validity of a quantitative respiratory frequency (f(R)) analysis to detect the ventilatory threshold (theta(Vent)) and respiratory compensation point (RCP). Thirty-six amateur competitive cyclists completed a maximal graded exercise test on an electromagnetically-braked cycle ergometer. theta(Vent) and RCP were determined using multiple gas exchange criteria and by f(R) analysis (theta(Vent)f(R) and RCP(f(R))), employing an iterative least-squares linear regression technique. Fifteen subjects were excluded from the analyses due to a low signal-to-noise ratio and/or high risk for pseudo-threshold resulting from hyperventilation early in the exercise protocol. A Bland-Altman procedure for inter-analysis comparison completed on the remaining participants' data (n=21; age=29+/-7 years; height=177+/-9 cm; weight=76.0+/-15.8 kg; VO(2max)=4.415+/-0.971 lmin(-1); 58.7+/-10.7 ml kg(-1) min(-1)) revealed mean bias+/-95% Limits of Agreement (LOA) of 1.53+/-50.2 W for theta(Vent) and theta(Vent)f(R). The same inter-anlysis comparison (n=21) for RCP and RCP(f(R)) resulted in a mean bias+/-LOA of 12.6+/-26.9 W. The analysis techniques in the present investigation revealed substantial limits of agreement and/or bias for all estimations, and these data indicated f(R) analyses were unsatisfactory to determine theta(Vent) and RCP in trained cyclists.

Resting metabolic rate before exercise vs a control day.

Investigations on resting and recovery metabolism have used both preexercise and separate control-day measurements as a baseline for comparisons. The purpose of this study was to compare preexercise resting data with nonexercise control-day resting data. Seven active men aged 25 +/- 5 y and weighing 83.2 +/- 15.4 kg followed prescribed dietary (12-h fast) and activity (48-h abstinence) preparatory protocols and were scheduled to exercise for 60 min on three separate occasions. A fourth session involved no exercise (control) and included an extended rest period. Resting metabolic rate (RMR) and heart rate measured in a semirecumbent position were not significantly different among preexercise and control conditions. Respiratory exchange ratio (RER) increased as the control rest was extended to 120 min. Reliabilities for both RMR and RER were initially high but were decreased at the end of the extended rest. These results suggest that preexercise RMR data can be used as a baseline for comparison purposes. In addition, prolonging the rest period does not appear to improve the RMR or RER values.

Expired air temperature during steady-state running.

While some metabolic measurement systems measure expiratory temperature to standardize gas volumes, other systems use only an estimate. This study investigated the effect of prolonged exercise on expiratory temperature near the pneumotachometer to provide a basis for its estimation when actual measurement is unavailable. Seven active females each performed two 45-min treadmill runs at identical speeds (64.5% +/- 11.8% of VO2max) in which the pneumotachometer heater control was either set to 37 degrees C or turned off. Expired air temperatures were monitored with thermocouples at the nonrebreathing valve (VAL) and 1 cm upstream (UPS) and downstream (DNS) from the pneumotachometer screens. There were no temperature differences over time for any of the conditions, and there were no differences in the VAL or UPS temperatures between the heated and unheated conditions. DNS temperature was higher during the heated condition at all time periods (P < 0.01). Mean DNS temperatures for the heated and unheated condition were 30.2 +/- 1.0 degree C and 27.9 +/- 1.1 degrees C, respectively. We conclude that expired air temperatures near the pneumotachometer remain stable during extended steady-state exercise regardless of whether the pneumotachometer is heated or not.

Influence of fitness on susceptibility to noise-induced temporary threshold shift.

PURPOSE: Two earlier reports indicated that cardiovascular fitness attenuates susceptibility to noise-induced temporary threshold shift (TTS) in hearing sensitivity; however, other parameters of fitness also may be related to this phenomenon. This study investigated the association of three different physical fitness indicators on TTS. METHODS: Maximal aerobic power (VO2max), body composition. and recent activity history were determined in 33 normal-hearing females of various fitness levels. Audiometric thresholds were obtained at 2000, 3000, 4000, and 6000 Hz before and immediately after 10 min of exposure to 108-dB SPL narrow-band noise centered at 2000 Hz. RESULTS: All postnoise measurements were significantly less than prenoise measurements (P < 0.0001) with the greatest TTS occurring at 3000 Hz. Similarly, the strongest Pearson-product correlations for VO2max, % fat, and recent activity history with TTS occurred at 3000 Hz (r = -0.68, 0.60, -0.59, respectively; P < 0.05). Canonical correlation analysis indicated a moderate correlation between physical fitness and TTS (Rc = 0.71: P < 0.01). Individually, VO2max, % fat, and recent activity history had correlations of -0.70, 0.62, and -0.63, respectively, to the TTS canonical variable. CONCLUSIONS: From these results, we concluded that there is a moderate association of physical fitness and diminished temporary hearing loss experienced after noise exposure.

Effects of consecutive exercise days of jogging or cycling on the resting metabolic rate and nitrogen balance.

The resting metabolic rate (RMR) following recovery from level jogging, which includes an eccentric component, was hypothesized to be greater and remain elevated longer than following concentric cycling due to repair of exercise-induced muscle damage. Nine males participated in both a jogging and cycling protocol. RMR measurements were determined by indirect calorimetry before and on the seven mornings following three consecutive days of 45-min exercise sessions performed at equal energy expenditures. Daily protein intake and urinary nitrogen (N) output were measured throughout both protocols. No differences were observed in the resting oxygen consumption, respiratory exchange ratio, or heart rate between baseline measurements and from any of the postexercise days following the third exercise bout. Urinary N and the estimated N balance during postexercise also did not change from baseline values over time or mode x time. However, the overall estimated N balance for the jogging protocol was less positive than for the cycling protocol (p < 0.05). Muscular soreness was greater (p < 0.05) and lasted longer from the jogging protocol. Although, muscle damage may have been more severe in the jogging protocol, RMR and N balance were not different between the two exercise modes.

Long slow distance training in novice marathoners.

The purpose of this study was to determine the physiological and performance effects of two frequencies and volumes of long slow distance (LSD) training in novice male and female marathoners. Subjects (N = 51) were healthy college students who had not previously run a marathon. They were matched on peak oxygen consumption (VO2peak) into a 6 d.wk-1 (G6) or a 4 d.wk-1 (G4) training group. Both groups trained at 60% to 75% of the heart rate reserve for 15 weeks but G4 trained with 20% less total volume. All groups responded similarly to the training by decreasing percent body fat and maximum heart rate and by increasing fat free mass and VO2peak. All groups significantly decreased the oxygen (O2) cost, lactate level, and heart rate at a submaximal running speed. Within the same gender, performance in the marathon was not different between groups. It was concluded that both training programs prepared subjects equally well to run a marathon.

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 (VE) was greater than the level VE. 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.

Effect of a sports food bar on fat utilisation and exercise duration.

The manufacturer claims that using the Access Fat Conversion Activity Bar increases fat utilisation, which would have a glycogen-sparing effect and delay the onset of fatigue from endurance exercise. This claim was tested using seven trained distance runners who performed two trials of treadmill running at 73% of VO2max to exhaustion. In a counterbalanced design, subjects ingested either one Access Bar with water or water only prior to treadmill running. Times to exhaustion for the control and Access treatment trials were 104.6 +/- 24.9 min and 93.9 +/- 21.4 min, respectively, and were not significantly different (p > .05). Differences between trials were not observed for the respiratory exchange ratio, blood lactate or glucose concentrations, plasma glycerol concentration, or perceived exertion. Based on results from this study, it was concluded that the Access Bar does not affect fat or carbohydrate utilisation and does not improve exercise endurance.

An inquiry-based learning model for an exercise physiology laboratory course.

We developed an inquiry-based learning model to better stimulate undergraduate students' cognitive development of exercise physiology laboratory concepts. The course core is the two independent research projects that students, working in small groups, complete during the last 9 wk of the semester. Student groups develop their own research question and hypothesis, design the experiment, collect and analyze the data, and report their findings to the rest of the class using presentation software. To help with success of the research projects, students are taken through a series of guided-inquiry laboratory activities during the initial 6 wk of the semester to develop laboratory skills and an understanding of the scientific process. Observations of student behaviors reflected a high level of enthusiasm and engagement in laboratory activities. Surveys, journal entries, and interviews indicated that students felt empowered by having ownership in their projects, which may be the key reason for the success of this model.

The effect of creatine supplementation on two 700-m maximal running bouts.

We investigated the effect of creatine supplementation on maximal running performance in a simulated track competition. Twelve competitive male runners were assigned to either a placebo or creatine supplementation group. Both groups completed two maximal 700-m running bouts 60 min apart on an outdoor track. A second identical trial was performed 7 days later, and for 5 days prior to the second trial, subjects ingested 20 g.day-1 of either creatine monohydrate or a placebo. Subjects in the placebo group ran 110.2 +/- 3.5 s and 110.4 +/- 3.0 s for the first trial and 108.5 +/- 2.9 s and 108.0 +/- 1.7 s for the second trial, while the creatine group ran 109.9 +/- 3.2 s and 110.4 +/- 3.6 s for the first trial and 109.7 +/- 3.3 s and 107.8 +/- 2.2 s for the second trial. There were no significant differences between groups by trial or Trial X Time for running time, postexercise blood lactate concentration, or body weight (p > .05). We concluded that creatine supplementation does not enhance performance of single or twice-repeated maximal running bouts lasting 90-120 s.