Evidence that the talk test can be used to regulate exercise intensity.

The Talk Test (TT) has been shown to be a surrogate of the ventilatory threshold and to be a viable alternative to standard methods of prescribing exercise training intensity. The TT has also been shown to be responsive to manipulations known to change physiologic function including blood donation and training. Whether the TT can be used independently to regulated training intensity is not known. Physically active volunteers (N = 16) performed an incremental exercise test to identify stages of the TT (Last Positive [LP], Equivocal [EQ], and Negative [NEG]). In subsequent, randomly ordered, 30-minute steady-state runs, the running velocity was regulated solely by "clamping" the TT response desired and then monitoring the response of conventional markers of exercise intensity (heart rate, blood lactate, rating of perceived exertion). All subjects were able to complete the LP stage, but only 13 of 16 and 2 of 16 subjects were able to complete the EQ and NEG stages, respectively. Physiologic responses were broadly within those predicted from the incremental exercise test and within the appropriate range of physiologic responses for exercise training. Thus, in addition to correlating with convenient physiological markers, the TT can be used proactively to guide exercise training intensity. The LP stage produced training intensities compatible with appropriate training intensity in healthy adults and with recovery sessions or long duration training sessions in athletes. The EQ and NEG stages produced intensities compatible with higher intensity training in athletes. The results demonstrate that the TT can be used as a primary method to control exercise training intensity.

Preexercise intermittent passive stretching and vascular function after treadmill exercise.

Acute aerobic exercise stress is associated with decreased endothelial function that may increase the likelihood of an acute cardiovascular event. Passive stretch (PS) elicits improvements in vascular function, but whether PS can be performed before exercise to prevent declines in vascular function remains unknown. This strategy could be directly applicable in populations that may not be able to perform dynamic exercise. We hypothesized that preexercise PS would provide better vascular resilience after treadmill exercise. Sixteen healthy college-aged males and females participated in a single laboratory visit and underwent testing to assess micro- and macrovascular function. Participants were randomized into either PS group or sham control group. Intermittent calf PS was performed by having the foot in a splinting device for a 5-min stretch and 5-min relaxation, repeated four times. Then, a staged V̇o2 peak test was performed and 65% V̇o2 peak calculated for subjects to run at for 30 min. Near-infrared spectroscopy-derived microvascular responsiveness was preserved with the PS group [(pre: 0.53 ± 0.009%/s) (post: 0.56 ± 0.012%/s; P = 0.55)]. However, there was a significant reduction in the sham control group [(pre: 0.67 ± 0.010%/s) (post: 0.51 ± 0.007%/s; P = 0.05)] after treadmill exercise. Flow-mediated vasodilation (FMD) of the popliteal artery showed similar responses. In the PS group, FMD [(pre: 7.23 ± 0.74%) (post: 5.86 ± 1.01%; P = 0.27)] did not significantly decline after exercise. In the sham control group, FMD [(pre: 8.69 ± 0.72%) (post: 5.24 ± 1.24%; P < 0.001)] was significantly reduced after treadmill exercise. Vascular function may be more resilient if intermittent PS is performed before moderate-intensity exercise and, importantly, can be performed by most individuals.NEW & NOTEWORTHY We demonstrate for the first time that popliteal artery and gastrocnemius microvascular responsiveness after acute aerobic exercise are reduced. The decline in vascular function was mitigated in those who performed intermittent passive stretching before the exercise bouts. Collectively, these findings suggest that intermittent passive stretching is a novel method to increase vascular resiliency before aerobic activity.

Body Composition, Energy Availability, Risk of Eating Disorder, and Sport Nutrition Knowledge in Young Athletes.

Young athletes may be at risk for low energy availability (LEA) or dietary habits that are indicative of eating disorders. Thus, the purpose of the current study was to investigate the prevalence of LEA among high school athletes and examine those at risk for eating disorders. A secondary aim was to examine relationships between sport nutrition knowledge, body composition, and LEA. METHODS: 94 male (n = 42) and female (n = 52) mean ± SD age: 18.09 ± 2.44 y; height: 172.6 ± 9.8 cm; body mass: 68.7 ± 14.5 kg; BMI: 22.91 ± 3.3 kg·m-2) athletes completed a body composition assessment and electronic versions of the abridged sports nutrition knowledge questionnaire (ASNK-Q), brief eating disorder in athletes questionnaire (BEDA-Q), and the low energy availability for females questionnaire (LEAF-Q; females only). RESULTS: 52.1% of female athletes were classified as being at risk for LEA. Moderate inverse relationships existed for computed LEAF-Q scores and BMI (r = -0.394; p < 0.01). A total of 42.9% of males (n = 18) and 68.6% of females (n = 35) were at risk for eating disorders, with females being at greater risk (p < 0.01). Body fat percentage was a predictor (ß = -0.095; p = -0.01) for eating disorder risk status. For every 1 unit increase in body fat percentage, athletes were 0.909 (95% CI: 0.845-0.977) times less likely to be classified as at risk for an eating disorder. Male (46.5 ± 13.9) and female (46.9 ± 11.4) athletes scored poorly on the ASNK-Q, with no differences between sex (p = 0.895). CONCLUSIONS: Female athletes were at a greater risk for eating disorders. No relationships existed between sport nutrition knowledge and %BF. Female athletes with a higher %BF had a lower risk for an eating disorder and risk for LEA.

Validation of skinfold equations and alternative methods for the determination of fat-free mass in young athletes.

Intoduction: To cross-validate skinfold (SKF) equations, impedance devices, and air-displacement plethysmography (ADP) for the determination of fat-free mass (FFM). Methods: Male and female youth athletes were evaluated (n = 91[mean ± SD] age: 18.19 ± 2.37 year; height: 172.1 ± 9.8 cm; body mass: 68.9 ± 14.5 kg; BMI: 23.15 ± 3.2 kg m-2; body fat: 19.59 ± 6.9%) using underwater weighing (UWW), ADP, and SKF assessments. A 3-compartment (3C) model (i.e., UWW and total body water) served as the criterion, and alternate body density (Db) estimates from ADP and multiple SKF equations were obtained. Validity metrics were examined to establish each method's performance. Bioelectrical impedance analysis (BIA), bioimpedance spectroscopy (BIS), and the SKF equations of Devrim-Lanpir, Durnin and Womersley, Jackson and Pollock (7-site), Katch, Loftin, Lohman, Slaughter, and Thorland differed from criterion. Results: For females, Pearson's correlations between the 3C model and alternate methods ranged from 0.51 to 0.92, the Lin's concordance correlation coefficient (CCC) ranged from 0.41 to 0.89, with standard error of the estimate (SEE) ranges of 1.9-4.6 kg. For SKF, the Evans 7-site and J&P 3 Site equations performed best with CCC and SEE values of 0.82, 2.01 kg and 0.78, 2.21 kg, respectively. For males, Pearson's correlations between the 3C model and alternate methods ranged from 0.50 to 0.95, CCC ranges of 0.46-0.94, and SEE ranges of 3.3-7.6 kg. For SKF, the Evans 3-site equation performed best with a mean difference of 1.8 (3.56) kg and a CCC of 0.93. Discussion: The Evans 7-site and 3-site SKF equations performed best for female and male athletes, respectively. The field 3C model can provide an alternative measure of FFM when necessary.

Effect of Running Velocity Variation on the Aerobic Cost of Running.

The aerobic cost of running (CR), an important determinant of running performance, is usually measured during constant speed running. However, constant speed does not adequately reflect the nature of human locomotion, particularly competitive races, which include stochastic variations in pace. Studies in non-athletic individuals suggest that stochastic variations in running velocity produce little change in CR. This study was designed to evaluate whether variations in running speed influence CR in trained runners. Twenty competitive runners (12 m, VO2max = 73 ± 7 mL/kg; 8f, VO2max = 57 ± 6 mL/kg) ran four 6-minute bouts at an average speed calculated to require ~90% ventilatory threshold (VT) (measured using both v-slope and ventilatory equivalent). Each interval was run with minute-to-minute pace variation around average speed. CR was measured over the last 2 min. The coefficient of variation (CV) of running speed was calculated to quantify pace variations: ±0.0 m∙s-1 (CV = 0%), ±0.04 m∙s-1 (CV = 1.4%), ±0.13 m∙s-1(CV = 4.2%), and ±0.22 m∙s-1(CV = 7%). No differences in CR, HR, or blood lactate (BLa) were found amongst the variations in running pace. Rating of perceived exertion (RPE) was significantly higher only in the 7% CV condition. The results support earlier studies with short term (3s) pace variations, that pace variation within the limits often seen in competitive races did not affect CR when measured at running speeds below VT.

Summated Hazard Score as a Powerful Predictor of Fatigue in Relation to Pacing Strategy.

During competitive events, the pacing strategy depends upon how an athlete feels at a specific moment and the distance remaining. It may be expressed as the Hazard Score (HS) with momentary HS being shown to provide a measure of the likelihood of changing power output (PO) within an event and summated HS as a marker of how difficult an event is likely to be perceived to be. This study aimed to manipulate time trial (TT) starting strategies to establish whether the summated HS, as opposed to momentary HS, will improve understanding of performance during a simulated cycling competition. Seven subjects (peak PO: 286 ± 49.7 W) performed two practice 10-km cycling TTs followed by three 10-km TTs with imposed PO (±5% of mean PO achieved during second practice TT and a self-paced TT). PO, rating of perceived exertion (RPE), lactate, heart rate (HR), HS, summated HS, session RPE (sRPE) were collected. Finishing time and mean PO for self-paced (time: 17.51 ± 1.41 min; PO: 234 ± 62.6 W), fast-start (time: 17.72 ± 1.87 min; PO: 230 ± 62.0 W), and slow-start (time: 17.77 ± 1.74 min; PO: 230 ± 62.7) TT were not different. There was a significant interaction between each secondary outcome variable (PO, RPE, lactate, HR, HS, and summated HS) for starting strategy and distance. The evolution of HS reflected the imposed starting strategy, with a reduction in PO following a fast-start, an increased PO following a slow-start with similar HS during the last part of all TTs. The summated HS was strongly correlated with the sRPE of the TTs (r = 0.88). The summated HS was higher with a fast start, indicating greater effort, with limited time advantage. Thus, the HS appears to regulate both PO within a TT, but also the overall impression of the difficulty of a TT.

25 Years of Session Rating of Perceived Exertion: Historical Perspective and Development.

The session rating of perceived exertion (sRPE) method was developed 25 years ago as a modification of the Borg concept of rating of perceived exertion (RPE), designed to estimate the intensity of an entire training session. It appears to be well accepted as a marker of the internal training load. Early studies demonstrated that sRPE correlated well with objective measures of internal training load, such as the percentage of heart rate reserve and blood lactate concentration. It has been shown to be useful in a wide variety of exercise activities ranging from aerobic to resistance to games. It has also been shown to be useful in populations ranging from patients to elite athletes. The sRPE is a reasonable measure of the average RPE acquired across an exercise session. Originally designed to be acquired ∼30 minutes after a training bout to prevent the terminal elements of an exercise session from unduly influencing the rating, sRPE has been shown to be temporally robust across periods ranging from 1 minute to 14 days following an exercise session. Within the training impulse concept, sRPE, or other indices derived from sRPE, has been shown to be able to account for both positive and negative training outcomes and has contributed to our understanding of how training is periodized to optimize training outcomes and to understand maladaptations such as overtraining syndrome. The sRPE as a method of monitoring training has the advantage of extreme simplicity. While it is not ideal for the precise recording of the details of the external training load, it has large advantages relative to evaluating the internal training load.

Rapidity of responding to a hypoxic challenge during exercise.

The ability to modify power output (PO) in response to a changing stimulus during exercise is crucial for optimizing performance involving an integration system involving a performance template and feedback from peripheral receptors. The rapidity with which PO is modified has not been established, but would be of interest relative to understanding how PO is regulated. The objective is to determine the rapidity of changes in PO in response to a hypoxic challenge, and if change in PO is linked to changes in arterial O(2) saturation (S (a)O(2)). Well-trained cyclists performed randomly ordered 5-km time trials. Subjects began the trials breathing room air and switched to hypoxic (HYPOXIC, F(I)O(2) = 0.15) or room (CONTROL, F(I)O(2) = 0.21) air at 2 km, then to room air at 4 km. The time delay to begin decreasing S (a)O(2) and PO and to recover S (a)O(2) and PO on to room air was compared, along with the half time (t (1/2)) during the HYPOXIC trial. Mean S (a)O(2) and PO between 2 and 4 km were significantly different between CONTROL and HYPOXIC (94 +/- 2 vs. 83 +/- 2% and 285 +/- 16 vs. 245 +/- 19 W, respectively). There was no difference between the time delay for S (a)O(2) (31.5 +/- 12.8 s) and in PO (25.8 +/- 14.4 s) or the recovery of S (a)O(2) (29.0 +/- 7.7 s) and PO (21.5 +/- 12.4 s). The half time for decreases in S (a)O(2) (56.6 +/- 14.4 s) and in PO (62.7 +/- 20.8 s) was not significantly different. Modifications of PO due to the abrupt administration of hypoxic air are related to the development of arterial hypoxemia, and begin within approximately 30 s.

Perception of fatigue during simulated competition.

BACKGROUND: Previous studies suggest that the rating of perceived exertion (RPE) increases during steady-state, open-loop exercise in proportion to the relative time to fatigue. This suggests that RPE is scalar and integrates physiological status and homeostatic disturbances. PURPOSE: This study assessed the relationship between the rate of change in RPE, and relative distance in time trials at distances of 2.5, 5, and 10 km. It also assessed the rate of change in RPE during 5-km time trials while breathing hypoxic air. METHODS: The subjects were well-conditioned cyclists. In part 1, each subject completed habituation time trials, and then randomly ordered time trials at each distance. The category ratio RPE was measured in 10% increments throughout each trial. In part 2, each subject completed three 5-km time trials while breathing different inspired gas mixtures (FiO2 = 0.2093 throughout the trial, FiO2 = 0.15 between 2 and 4 km, and FiO2 = 0.15 between 2.5 and 4 km). RPE was measured at 10% increments. RESULTS: In part 1, when RPE was plotted against relative distance, there was no significant difference in the growth of RPE at proportional distances. In part 2, the decrease in power output during the hypoxic segments was sufficient that the growth of RPE was the same at each proportional distance. In both parts of the study, an RPE of 5 (hard) was achieved after 20% of the time trial distance, and an RPE of 8 was achieved after 80% distance. CONCLUSIONS: This study supports the hypothesis that RPE increases similarly in relation to relative distance, regardless of the distance performed, and it suggests that the perception of effort has scalar properties.

Pacing Strategy in Short Cycling Time Trials.

PURPOSE: To reach top performance in cycling, optimizing distribution of energy resources is crucial. The purpose of this study was to investigate power output during 250-m, 500-m, and 1000-m cycling time trials and the characteristics of the adopted pacing strategy. METHODS: Nine trained cyclists completed an incremental test and 3 time trials that they were instructed to finish as quickly as possible. Preceding the trials, peak power during short sprints (PP sprint) and gross efficiency (GE) were measured. During the trials, power output and oxygen consumption were measured to calculate the contribution of the aerobic and anaerobic energy sources. After the trial GE was measured again. RESULTS: Peak power during all trials (PPTT) was lower than PP sprint. In the 250-m trial the PPTT was higher in the 1000-m trial (P = .008). The subjects performed a significantly longer time at high intensity in the 250-m than in the 1000-m (P = .029). GE declined significantly during all trials (P < .01). Total anaerobically attributable work was less in the 250-m than in the 500-m (P = .015) and 1000-m (P < .01) trials. CONCLUSION: The overall pacing pattern in the 250-m trial appears to follow an all-out strategy, although peak power is still lower than the potential maximal power output. This suggests that a true all-out pattern of power output may not be used in fixed-distance events. The 500-m and 1000-m had a more conservative pacing pattern and anaerobic power output reached a constant magnitude.

Pattern of energy expenditure during simulated competition.

PURPOSE: To determine how athletes spontaneously use their energetic reserves when the only instruction was to finish in minimal time, and whether experience from repeated performance changes the strategy of recreational athletes. METHODS: Recreational road cyclists/speed skaters (N = 9) completed three laboratory time trials of 1500 m on a windload braked cycle. The pattern of energy use was calculated from total work and from the work attributable to aerobic metabolism, which allowed computation of anaerobic energy use. Regional level speed skaters (N = 8) also performed a single 1500-m time trial with the same protocol and measurements. RESULTS: The serial trials were completed in (mean +/- SD) 133.8 +/- 6.6, 133.9 +/- 5.8, 133.8 +/- 5.5 s (P > 0.05 among trials); and in 125.7 +/- 10.9 s in the skaters (P < 0.05 vs cyclists). The [OV0312]O(2peak) during the terminal 200 m was similar within trials (3.23 +/- 0.44, 3.34 +/- 0.44, 3.30 +/- 0.51 (P > 0.05)) versus 3.91 +/- 0.68 L.min-1 in the skaters (P < 0.05 vs cyclists). In all events, the initial power output and anaerobic energy use was high and decayed to a more or less constant value ( approximately 25% of peak) over the remainder of the event. Contrary to predictions based on an assumed "all out" starting strategy, the subjects reserved some of their ability to perform anaerobic work for a terminal acceleration. The total work accomplished was not different between trials (43.53, 43.78, and 47.48 kJ in the recreational athletes, or between the cyclists and skaters (47.79 kJ). The work attributable to anaerobic sources was not different between the rides (20.67, 20.53, and 21.12 kJ in the recreational athletes). In the skaters, the work attributable to anaerobic sources was significantly larger versus the cyclists (24.67 kJ). CONCLUSION: Energy expenditure during high-intensity cycling seems: 1) to be expended in a manner that allows the athlete to preserve an anaerobic energetic contribution throughout an event, 2) does not appear to have a large learning effect in already well trained cyclists, and 3) anaerobic energy expenditure may be the performance discriminating factor among groups of athletes.

An approach to estimating gross efficiency during high-intensity exercise.

PURPOSE: Gross efficiency (GE) is coupling power production to propulsion and is an important performance-determining factor in endurance sports. Measuring GE normally requires measuring VO(2) during submaximal exercise. In this study a method is proposed to estimating GE during high-intensity exercise. METHODS: Nineteen subjects completed a maximal incremental test and 2 GE tests (1 experimental and 1 control test). The GE test consisted of 10 min cycling at 50% peak power output (PPO), 2 min at 25 W, followed by 4 min 100% PPO, 1 min at 25 W, and another 10 min at 50% PPO. GE was determined for the 50%-PPO sections and was, for the second 50%-PPO section, back-extrapolated, using linear regression, to the end of the 100%-PPO bout. RESULTS: Back-extrapolation of the GE data resulted in a calculated GE of 15.8% ± 1.7% at the end of the 100%-PPO bout, in contrast to 18.3% ± 1.3% during the final 2 min of the first 10-min 50%-PPO bout. CONCLUSION: Back-extrapolation seems valuable in providing more insight in GE during high-intensity exercise.

Rapidity of response to hypoxic conditions during exercise.

UNLABELLED: Previous studies have found decreases in arterial oxygen saturation to be temporally linked to reductions in power output (PO) during time-trial (TT) exercise. The purpose of this study was to determine whether preexercise desaturation (estimated from pulse oximetry [SpO2]), via normobaric hypoxia, would change the pattern of PO during a TT. PURPOSE: The authors tested the hypothesis that the starting PO of a TT would be reduced in the EARLY trial secondary to a reduced SpO2 but would not be reduced in LATE until ~30 s after the start of the TT. METHODS: Eight trained cyclists/triathletes (4 male, 4 female) performed 3 randomly ordered 3-km TTs while breathing either room air (CONTROL) or hypoxic air administered 3 min before the start of the TT (EARLY) or at the beginning of the TT (LATE). RESULTS: There was no effect of hypoxia on PO during the first 0.3 km of either the EARLY or the LATE trial compared with CONTROL, although there was a significant decrease in pre-TT SpO2 in EARLY vs CONTROL and LATE. The time for PO to decrease was ~40 s after the start of the TT in both EARLY and LATE. CONCLUSIONS: The results support the strong effect of the preexercise template on the pattern of PO during simulated competition and suggest that reductions in SpO2 are not direct signals to decrease PO.