A new theory proposes that initial success increases the likelihood of subsequent success by creating three types of momentum effects: frequency, intensity and duration. Using a large data set (11,015 tournament results from four consecutive PGA Tour seasons), the present study is the first to examine these three effects and the relationship between momentum and elite performance. Results showed that performance successes measured with four outcome variables (making a “cut”, top 30, 20, 10 finishes) not only occurred in sequence, rather than randomly, but that higher-ranked players were able to put together more frequent and more lasting strings of successful performances. They also bounced back faster as indicated by shorter durations of missed cuts, top 30, 20 and 10 performances. The data suggest that better players are in part better because they create more occurrences of momentum and ride them longer. When these momentum influences were removed from regressions analysis, eta squares were reduced to trivial effect sizes, thereby demonstrating the powerful effect of momentum and simultaneously ruling out any meaningful role for randomness. As a whole, the results support the theory and suggest that momentum is a force that explains elite performance and the way in which better players consistently achieve better results than lower-ranked competitors. Although the analyses were based on overt indicators of behavioral momentum, it is noted that the causes and effects of momentum are psychological. Momentum affects and is affected by conscious and nonconscious cognitions and thoughts. Journal of Nature and Science (JNSCI), 3(3):e325, 2017

Golf’s governing bodies’ recent decision to ban all putting styles “anchoring one end of the club against the body” bridges an important practical problem with psychological theory. We report the first experiment testing whether anchoring provides technical and/or psychological advantage in competitive performance. Many “greats” of professional golf from Arnold Palmer and Jack Nicklaus to Tiger Woods have argued against anchoring, believing that it takes “nerves” out of competitive performance and therefore artificially levels the playing field. To shed more light on the issue, we tested participants’ performance with anchored and unanchored putters under low and high pressure when controlling for the putter length. We found no statistically significant evidence for a technical advantage due to anchoring but a clear psychological advantage: participants who anchored their putters significantly outperformed unanchored counterparts under high, but not low, pressure. Results provide tentative evidence for the ban’s justification from a competitive standpoint. However, before any definite conclusions can be made, more research is needed when using high-level golfers.

One of the most fundamental characteristics about humans is their desire for success, especially in highly competitive societies. What does it take to be successful? Is success simply a matter of better performance, and if so, what specifically is it about performance that determines success? A long research tradition suggests that psychological momentum (PM) plays a critical role in goal pursuit and achievement. Accordingly, sequential runs of success are an essential feature of high levels of performance, meaning that better performers perceive and experience momentum of success more frequently, ride it as long as they can, and as a result, become more successful in the end. Theoretically, momentum is a principle vehicle of performance that will significantly augment future success and facilitate goal achievement. Consequently, an overall performance consists of occurrences of momentum that vary in frequency and duration. The higher the frequency and the higher the duration, the more likely is success. Research suggests that the main psychological processes that underpin momentum effects are confidence, perceived competence, and internal (ability-skill) attributions. Based upon related research, it is hypothesized that PM starts as a conscious process but subsequently becomes a major facilitator of nonconscious automatic execution of human behavior and performance.

The accuracy of air displacement plethysmography (ADP) is known to be affected by isothermal air trapped in body and scalp hair. Previous research indicates the Lycra swim cap is deficient in compressing isothermal air from scalp hair, whereas a Silicone swim cap may provide better hair compression, thereby mitigating the underestimation of percent body fat (%fat) (Dooly and Dotson, 2013). PURPOSE: To compare the effect of a Silicone vs Lycra swim cap on ADP estimation of %fat. METHODS: Thirty-six euhydrated males (mean: age=28.1 yrs.; ht=177.8 cm; wt=87.3 kg) underwent ADP assessment with and without swim caps, followed by total body shaving experimental design. Calibration and assessment procedures followed manufacturer’s recommended guidelines. RESULTS: In comparison with subjects’ hairless no cap condition, their ADP estimates without any cap significantly (p=0.001) underestimated %fat by 11.6% (%fat =18.8% vs 21.2%). Use of a Lycra cap improved upon the no cap underestimation, but continued to significantly (p=0.001) underestimate subjects’ hairless no cap condition by 7.2%. In comparison, use of a silicone cap resulted in the smallest but still significant 5.0% (p=0.001) underestimation of the %fat for the hairless no cap condition. Regression analysis and Bland Altman plot certified across the %fat range of 5% to 45%, underestimation was uniformly constant for each of the cap conditions with a standard error of estimate of 1.1 and 1.5 for Silicone and Lycra caps respectfully. CONCLUSION: Silicone caps, in comparison with Lycra caps, are more effective in mitigating the influence of trapped isothermal air on ADP estimation of %fat.

To declare a phenomenon an illusion would require no logical (theoretical) and empirical support for it after exhaustive research. Yet both types of evidence for psychological momentum (PM) abound in the literature, from individual sport performance to mutual fund investing. For example, it is well established that momentum-based investing provides consistent outperformance. However, in their commentary, the authors focus narrowly on one segment of sporting behavior, especially basketball studies, in which "hot hand" has only been tested based on 1 performance criterion-shooting percentages or probabilities-when a true test of "hotness" would require inclusion of multiple performance indicators. These studies are also marred by major theoretical and methodological deficiencies. Coupled with the propositional and provisional nature of scientific knowledge, one is left with no basis for making generalized statements about illusion and randomness of PM. As Gleiser (2014, p. 44) so eloquently states, "Data without theory is lame; theory without data is blind." To move forward, we have formulated the theoretical parameters of the phenomenon and show evidence indicating that performance successes not only occur in sequence, but higher-ranked players are able to put together more frequent and more lasting strings of successful performances; they also bounce back more quickly from failures. All in all, PM is alive and well. Its theoretical properties have been put forth for the first time, and empirical evidence is mounting for its effects in various domains of human behavior and performance.

Whether trying to win Presidential primaries, trading stocks, or playing sports, performance-enhancing effects of psychological momentum (PM) are widely accepted. But, does initial success (S1) lead to subsequent success (S2) in and of itself due to increased know-how on one's and opponents’ performance or because it creates psychological force (momentum) that mediates this relationship? We review research on the phenomenon and show its strong empirical foundations in various domains of human performance. To advance research, we present an organizing theoretical framework that proposes both mediating and moderating effects of PM as mechanisms to explain why success breeds success in general. Initial success is critical for PM and has 3 types of effects: intensity, frequency, and duration. Whether performing alone (trader) or against an opponent (tennis player), perceptions of self as a performer (Sp) and of opponent as a performer (Op) are at the center of PM. The theory posits that the more the initial success separates the two (Op/Sp), the greater the PM. These and associated perceptions, however, have to turn into an increased subjective probability of winning or succeeding before PM becomes a psychological force. Evidence supports the mediating mechanism since initial success increases PM, which in turn enhances subsequent success. When initial success with PM leads to a greater likelihood of subsequent success than without PM, PM then modifies (“moderates”) the S1–S2 relationship without PM's independent effect on S2. There is also tentative evidence for a moderated mediation effect as the influence of PM seems to be greater for male than female performers. Areas of future research are highlighted.

PURPOSE This study examined the trend of varying volumes of exercise on the risk factors embodying the metabolic syndrome in sedentary women (n = 27, age 49.2±5.4 yrs). METHODS Subjects exhibited risk profiles to at least three risk factors in waist circumference, triglyceride (TRIG), high-density lipoprotein (HDL), high blood pressure (SBP and/or DBP) and/or fasting glucose (GLUC) as detailed in the ATP III report. The subjects performed cardiovascular exercise three times per week for three months at initial volumes of 600 kcal/wk (n = 8), 800 kcal/wk (n = 11), or 1000 kcal/wk (n = 8) with no modifications in diet. Changes in metabolic syndrome risk factors, body composition and aerobic fitness measures related to total kilocalories per week (TKW) and kilocalories per kilogram of body weight per week (KKW) were assessed by multiple regression analysis. RESULTS Significant (p < 0.05) pre to post mean changes for SBP and DBP and total treadmill time (TTT) and near significant (p < 0.10) mean changes for HDL and TRIG were observed unrelated to a dose response as defined by TKW or KKW. However, significant dose response relationships between pre to post TC (p < 0.000), HDL (p < 0.001) and LDL (p < 0.003) changes and TKW were observed. Similarly, significant dose response relationships between pre to post GLUC, TTT, and waist to hip ratio changes and KKW were observed. Of clinical significance, following exercise intervention, seven subjects (25.9%) reduced the total number of metabolic syndrome risk factors to less than three, while eleven (40.7%) eliminated at least one risk factor. CONCLUSIONS Factors of the metabolic syndrome can be favorably changed by aerobic training.

Background. Genetic and environmental hypotheses may explain why normotensive persons at high risk of developing hypertension often exhibit greater cardiovascular reactivity to stressors than those at low risk. Methods: Pearson's correlation was used to evaluate reproducibility and independent t test to compare the cardiovascular responses to 30 W of exercise of normotensive young adult African-American women with positive and negative parental histories (PH) of hypertension (PH+, n = 23; PH-, n = 20). Results: Correlations were significant for duplicate measurements. The effects of PH on blood pressure measured at rest and during exercise were not statistically significant (P > 0.1). A nearly significant trend for greater resting VO2 (P = 0.08) was detected in the PH- than in the PH+ group (3.67 +/- 0.18 versus 3.26 +/- 0.14 mL/kg/min). Conclusion: A hyper-reactive blood pressure response to exercise, characteristic of the evolution of hypertension, may not be present among the normotensive female offspring of hypertensive African Americans. The significance of an 11 % intergroup difference in the mean resting VO2 observed in this study is unclear.

PURPOSE The purpose of this study was to examine the effects of hydration status on the estimation of body composition by Air Displacement Plethysmography (ADP) and Dual Energy X-ray Absorptiometry (DEXA). METHODS Twenty healthy normal-weight college age males (n=10) and females (n=10) were assessed for urine specific gravity (USG) via refractometer, and percent body fat (%BF) by ADP and DEXA at euhydration and following 1%, 2% and 3% dehydration induced by physical exercise in a climate control chamber. Assessments followed procedures delineated by manufacturer's specifications. Assessment of heart rate, skin temperature, and respiratory rate were made at euhydration and following each dehydration condition to insure subjects' return to baseline prior to ADP and DEXA. Mean differences among hydration conditions were assessed by a one between (Gender) by two within (Body Composition Methods, Hydration status) multiple factors repeated measures ANOVA. Post Hoc procedures with Bonferroni correction were employed to assess the significance of selected treatment comparisons. Significance levels for ANOVA and family-wise error rates were set at 0.05. RESULTS %BFADP, following 1%, 2% and 3% dehydration, for both males and females were significantly different from euhydration, while %BFDEXA did not significantly change across hydration conditions. %BFADP significantly underestimated %BFDEXA by 8.2% (females) and 11.3% (males) at euhydration and increased to 13.7% to 20.8% underestimation following dehydration for both genders. CONCLUSIONS Accepting DEXA as the reference standard, it is concluded that ADP underestimates %BF in both genders and this underestimation increases during periods of dehydration. This study demonstrates that hydration status should be controlled when assessing %BF by ADP.

PURPOSE The purpose of the study was to examine the effects of hydration status on body composition by Near Infrared Interactance (NIR), Bioelectrical Impedance Analysis (BIA), Air Displacement Plethysmography (ADP) and Dual Energy X-ray Absorptiometry (DEXA). METHODS Forty healthy college age males (n=20) and females (n=20) were assessed for percent body fat (%BF) by NIR, BIA, ADP and DEXA at initial visit, after euhydration and 1%, 2% and 3% dehydration. Mean differences among hydration conditions were assessed with a one between (Gender) by two within (Body Composition Methods, Hydration Status) repeated measures ANOVA. Selected orthogonal contrasts, and Post Hoc procedures with Bonferroni correction were employed to assess the influence of methods and hydration status on % BF. Significance levels were set at 0.05. RESULTS Euhydration did not significantly affect NIR and BIA assessment of %BF. However, euhydration significantly influenced ADP assessment of %BF among females. Dehydration did not significantly affect NIR assessment of %BF among females and only at extreme dehydration (> 2%) among males. Dehydration also did not significantly affect BIA assessment of %BF among males, but did significantly affect %BF among females. Dehydration significantly affected ADP assessment of %BF among both male and female subjects. Hydration status did not significantly influence DEXA assessment of %BF. At euhydration %BFDEXA was underestimated by NIR, BIA and ADP by 7%, 9% and 15%, respectively. Underestimation increased with dehydration levels for NIR (10%-13%), BIA (13%-17%) and ADP (22%-26%). Underestimation tended to be constant for NIR and BIA, but variable within subjects for ADP. CONCLUSIONS Accepting DEXA as the reference standard, it is concluded that NIR, BIA and ADP underestimate %BF in both genders and this underestimation increases during periods of dehydration. This study demonstrates that hydration status should be controlled when assessing %BF by NIR, BIA and ADP.

PURPOSE:Exaggerated blood pressure (BP) response during physical exertion is associated with increased risk for cardiovascular events. Furthermore, it may be the predisposing factor for myocardial infarction triggered by physical exertion. The authors have shown that systolic BP achieved after 6 minutes of exercise is the strongest predictor of left ventricular hypertrophy. Furthermore, a 37 mm Hg increase in systolic BP above resting BP at 6 minutes of exercise was the threshold for left ventricular hypertrophy. The purpose of this study was to determine predictors of exercise BP response in normotensive and hypertensive women. METHODS:An exercise tolerance test (Bruce) was performed by 1411 normotensive (resting BP < 140/90 mm Hg) and hypertensive (resting BP > or = 140/90 mm Hg) women. These women were faculty, students, and staff at the University of Maryland, College Park, Maryland, and the George Washington University Medical Center, as well as patients undergoing a routine exercise tolerance test at West Coast Cardiology, Pinellas Park, Florida. Two fitness categories (low-fit and high-fit) were established on the basis of treadmill time to exhaustion adjusted for age. RESULTS:Significant associations were observed among the 6-minute exercise BP and age, body mass index, resting systolic and diastolic BP, heart rate, and exercise time to exhaustion. In a stepwise multiple-regression analysis, the determinants of BP after 6 minutes of exercise were resting systolic BP and treadmill time to exhaustion (R2 = 0.36) for normotensive women and treadmill time to exhaustion and resting systolic BP (R2 = 0.30) for hypertensive women. When fitness categories were contrasted, low-fit women in both the normotensive and hypertensive categories had higher BP and rate-pressure product after 6 minutes of exercise than the high-fit women (P <.05). CONCLUSIONS:Resting systolic BP and cardiorespiratory fitness are determinants of a submaximal exercise BP response for both hypertensive and normotensive women. Low cardiorespiratory fitness is associated with a higher BP response during submaximal exercise, suggesting that increased fitness may attenuate this abnormal rise in BP. Thus, low- to moderate-intensity physical activities for most days of the week should be encouraged for all women to increase cardiorespiratory fitness. This is likely to attenuate an abnormal rise in systolic BP that may occur during routine daily activities and protect against the associated health consequences.

PURPOSE: The purpose of this study was to determine the effects of exercising above and below the lactate threshold (LAT), upon excess post-exercise oxygen consumption magnitude (EPOCmag) and duration (EPOCdur) among average fit college aged women. METHODS: Thirteen females, ages 19–34 years, taking prescribed birth control were recruited for this study. The volunteers were required to undergo testing over a nine day period (5 vists). Resting metabolic rate (RMR) was assessed over two visits following the bleeding portion of the menses. A ramped bicycle test was administered to determine peak VO2 and LAT. Blood samples were collected from an antecubital vein at rest, every two minutes during exercise, and throughout recovery. Ventilatory (breath by breath) and heart rate measurements were recorded during exercise and recovery. On separate days, workloads eliciting energy expenditures at 10% above (LATabove) and below (LAT-below) the individual LATs (Weltman, et. al. 1990) were continued until 300 kcals were expended. During recovery, heart rate, respiratory exchange ratio (RER), and VO2 were measured until metabolic rates returned within + 5% of the baseline RMR. RESULTS: EPOCdur was significantly greater (p < 0.05) for LATabove (61.49 ± 8.73 min) than LAT-below (30.72 ± 4.81 min). EPOCmag was also significantly greater (p < 0.05) for LATabove (24.29 ± 3.67 kcals) than LATbelow (13.28 ± 2.10 kcals). Exponential regression revealed LATabove induced exercise resulted in prolonged elevation of recovery energy expenditure. Single component exponential regression analyses revealed signifcantly (p < 0.05) slower recovery rates for LATabove (1/2 life = 1.38 min) compared to LATbelow (1/2 life = 1.06 min). CONCLUSIONS: Exercise above the LAT adds an additional energy cost component to the recovery dynamics. This study demonstrates the LAT should be considered when comparing exercise factors on EPOC magnitude and duration.

Purpose: The purpose of the study was to compare body composition during the follicular and luteal phases of the menstrual cycle. Methods: Eight women between the ages of 18 and 35 years with regular menses who were not receiving contraceptive medications participated in the study. Each woman reported to the laboratory on the first day of her cycle and every other day thereafter until the beginning of her next cycle. Temperature and weight were recorded at each of these visits. Additionally body composition was measured via bioelectrical impedance analysis (BIA), near infrared interactance (NIR), air displacement plethysmography (BodPod), and dual energy x-ray absorptiometry (DEXA) during the follicular phase (day 9 of the cycle) and luteal phase (5 days prior to the expected onset of the next menses). Results: Body weight on the day of body composition measurement during the follicular and luteal phases was 58.2 ± 5.44kg and 58.13 ± 5.48kg, respectively. The percent body fat for the follicular and luteal phases was 24.4 ± 6.24 and 23.86 ± 6.77 (DEXA), 22.83 ± 6.83 and 21.85 ± 6.03 (BodPod), 23.84 ± 3.10 and 22.28 ± 2.20 (BIA), and 23.19 ± 3.68 and 22.39 ± 3.65 (NIR). Conclusions: Percent body fat was significantly less during the luteal phase of the menstrual cycle as compared to the follicular phase. Since there was no significant change in weight between the follicular and luteal phases, the decrease in body fat observed in the luteal phase could be attributed to fluid shifts between compartments. These results indicate that the phase of the menstrual cycle must be controlled when determining body composition changes in female subjects. Additionally, BodPod, NIR and BIA underestimate body fat content compared to DEXA in the follicular as well as the luteal phase of the menstrual cycle.

It is likely that most individuals are 1–2% hypohydrated on a regular basis. Factors such as thirst, exercise, environmental conditions, diet, and menstruation can influence hydration status. There are several sources of error in body composition assessment that need to be addressed in order for a technique to prove reliable and valid. PURPOSE: To examine the effects of hydration status on the prediction of body composition using bioelectrical impedance analysis (BIA), near infrared interactance (NIR), and dual energy x-ray absorptiometry (DEXA). METHODS: Twenty healthy males and females ages 18 to 28 were recruited for this study. The subjects were required to undergo testing during a five-day period. The subjects were dehydrated in a climate control chamber (32°C[90 °F], 50% relative humidity) and engaged in physical exercise at a self-selected intensity, until they lost approximately 1%, 2%, and 3% of their pre-exercise body weight. Measurements including body weight and urine specific gravity and color were measured at each trial to assess hydration status. Body composition was assessed utilizing BIA and NIR initially on day 1, on day 4 at euhydration, following 1%-, 2%-, and 3%-dehydration, and during day 5 following rehydration. Body composition was assessed utilizing DEXA at the beginning of day 1, on day 4 at euhydration, and following 3%-dehydration. Measures of percent body fat (%BF) were examined for changes associated with each hydration condition. RESULTS: There were significant differences between %BFBIA, and %BFNIR, and %BFDEXA at the initial trial, 1%-, 2%-, and 3%-dehydration, and with rehydration. The %BFBIA and %BFNIR were significantly underestimated with increasing levels of dehydration while %BFDEXA did not significantly change. Gender also significantly influenced individual inter-method differences in the estimation of %BF. CONCLUSION: The results indicated that the estimations of %BF for BIA and NIR are significantly decreased with increasing levels of dehydration. Proper hydration should be ensured before %BF is estimated with BIA and NIR.

The purpose of this study was to examine the effects of hydration status on the estimation of body composition using near-infrared interactance (NIR), bioelectrical impedance analysis (BIA), and skinfolds (SK). Twelve euhydrated subjects (6 males, 6 females) 21–35 years of age were dehydrated to −1% and then −2% of total body weight in a sauna for approximately 100 minutes at 110 degrees F and 88% humidity. Body composition measures were taken pre and post −1% and −2% dehydration. Body composition measures were repeated after 5 days euhydration and following a 2% fluid hyper-hydration. A 3 (body composition procedure) × 5 (hydrate condition) repeated measures ANOVA followed by selected means comparisons with Bonferoni correction revealed BIA significantly underestimated (p < 0.05) % fat with dehydration and significantly overestimated (p < 0.05) % fat following hyperhydration. % fat was not significantly affected by alterations in hydration level with NIR or SK. However, there was a slight tendency to underestimate % fat with dehydration and overestimate % fat during hyper-hydration by NIR. SK demonstrated a non-significant decrease with dehydration with no effect in the hyper-hydrated state. BIA demonstrated the greatest pertubations in % fat estimation, followed by NIR, while SK showed the least pertubations with alterations in hydration status. These results emphasize the need to control hydration level prior to body composition measures, particularly with BIA. NIR and SK appear to be more resistant to changes in hydration status.Table

The purpose of this study was to investigate the predictive power of different methods of measuring body composition in African American (AA) and Caucasian (C) females. Subjects included 20 AA and 25 C aged 18–27. All subjects completed bioelectrical impedance analysis (BIA) using the equations of Lohman; seven-site skinfold (SK) according to Jackson et al.; near-infra-red (NIR) using the equations of Heyward et al.; and hydrostatic weighing (H) according to Brozek et al. The data was analyzed by regression and a 2 (race) × 4 (body composition method) ANOVA with repeated measures. There was no significant difference for race, regardless of body composition method (p > 0.05). There was no interaction for race × body composition method (p > 0.05). However, there were significant differences among methods independent of race (F = 22.45; p < 0.000). Difference contrasts (with Bonferroni correction) between estimation methods and hydrostatic weighing revealed BIA, regardless of race significantly overestimated % fat by H (p < 0.05). No other mean estimation differences were noted (p > 0.05). Regression diagnostics revealed that estimation methods exhibited unique estimation biases of % fat by H. BIA, regardless of race, tended to overestimate low % fat by H, while underestimating high % fat by H. Alternatively, NIR exhibited a tendency to underestimate low % fat by H while overestimating high % fat by H. However, SK exhibited a slight but insignificant (p > 0.05) tendency to overestimate % fat by H regardless of subjects % fat by H. These results suggest that body composition level (low-high) rather than racial differences may account for biases inherent in BIA, SK and NIR estimation methods.

640 Echocardiographically detected left ventricular hypertophy (LVH) is a powerful and independent predictor of cardiovascular events. Resting blood pressure (BP) is weakly associated with LVH, while a stronger association has been reported between LVH and exercise BP in men. However, it is not known if this relationship exists in women. We sought to determine predictors of left ventricular mass (LV mass) in normotensive (n=194;age=51±10) and hypertensive (n=115; age=57±8) women. All women were free of heart disease and antihypertensive medication. LVH (LVM Index ≥ 110) was present in 15% of the normotensive and 71% of the hypertensive women. Significant differences (p<0.05) between those with and without hypertension were also noted in age, resting BP, BMI and LV mass index. Multiple regression analysis with 15 selected independent variables, including resting systolic BP (RSBP), 6-minute exercise systolic BP (SBPII) and exercise time to exhaustion (ETE), revealed the following variables as the strongest predictors of LV mass: (Table)TableThus, SBP at 6 minutes of exercise is the strongest predictor of LV mass in normotensive and hypertensive.

1428 An exaggerated increase in exercise blood pressure (BP) is associated with risk for cardiovascular events even in those with normal resting BP. Fitness levels are associated with lower resting BP. Thus, we sought to determine if fitness levels were also associated with lower exercise BP in normotensive individuals. We assessed fitness and BP during a graded exercise test (Bruce Protocol), in 735 middle-aged (43±11) women. All were free of heart disease and antihypertensive medication. They were classified as Low-Fit (n=362) or High-Fit (n=373) based on exercise time to exhaustion (ETE), adjusted for age. Groups were similar in age and resting BP with significant differences in exercise BP (p<0.05); table). Multivariate regression revealed the strongest predictors of BP at 6 minutes of exercise, were ETE, resting BP and age (R2=0.46). For peak exercise BP the predictors were resting systolic BP and age (R2=0.30). The risk of having exaggerated BP during exercise (systolic BP ≥ 190 mm Hg), was 53% lower in the High-Fit vs the Low-Fit group (Odds Ratio=0.47; CI: 0.35-0.64).TableWe concluded that in middle-aged women: 1) physical fitness is associated with lower BP at sub-maximum and maximum exercise workloads; and 2) exaggerated BP response to exercise may be attenuated by increased physical fitness.