Physiological and perceptual responses during walking at set and preferred pace in normal and overweight adults.

BACKGROUND: This study aimed to investigate the influence of body weight, exercise modality, and pace on physiological and perceptual responses to determine the relation between perceptual and physiological responses. METHODS: Aerobically untrained, normal weight, and overweight males and females participated. Participants were randomly assigned to one exercise condition for a 1-mile walk. RESULTS: Prescribed pace resulted in a greater physiological stress than self-selected pace (all p < 0.001) through blood lactate (1.3 ± 0.4 vs 1.7 ± 0.5 mmol), systolic blood pressure (128.9 ± 10.3 vs 139.2 ± 13.2 mmHg), heart rate recovery (2.1 ± 1.7 vs 4.5 ± 2.6 min), oxygen consumption (15.1 ± 2.6 vs 18.1 ± 3.6 ml/kg/min), heart rate (111.7 ± 16.6 vs 134.4 ± 8.3 bpm), and energy expenditure (5.5 ± 1.4 vs 6.8 ± 1.7 kcal/min). Overweight individuals exhibited higher values than normal weight for heart rate (113 ± 8.8 vs 125.5 ± 13.2 bpm, p < 0.001), percentage of max heart rate (60.7 vs 69.0%, p < 0.001), percent of VO2peak (42.2 vs 55.6%, p < 0.001), and total energy expenditure (100.9 ± 27.4 vs 114.1 ± 33.5 kcal, p = 0.022). Greater perceived effort was seen on a treadmill (6.3 ± 0.5 vs 12.5 ± 2.0 RPE, p < 0.001) and at prescribed pace (6.5 ± 1.1 vs 8.9 ± 1.9 RPE, p < 0.001). CONCLUSION: A novel finding of this study was the increased physiological stress and perception of effort on a treadmill and at a prescribed pace, while total energy expenditure showed no significant differences. This could indicate an unfavorable perception and less affective response to the treadmill modality. These results indicate exercise at self-selected pace in preferred environments promotes enjoyable experiences with similar health benefits as those during prescribed higher intensity exercise.

Loss of flow responsive Tie1 results in ImpairedAortic valve remodeling.

The mechanisms regulating endothelial cell response to hemodynamic forces required for heart valve development, especially valve remodeling, remain elusive. Tie1, an endothelial specific receptor tyrosine kinase, is up-regulated by oscillating shear stress and is required for lymphatic valve development. In this study, we demonstrate that valvular endothelial Tie1 is differentially expressed in a dynamic pattern predicted by disturbed flow during valve remodeling. Following valvular endocardial specific deletion of Tie1 in mice, we observed enlarged aortic valve leaflets, decreased valve stiffness and valvular insufficiency. Valve abnormalities were only detected in late gestation and early postnatal mutant animals and worsened with age. The mutant mice developed perturbed extracellular matrix (ECM) deposition and remodeling characterized by increased glycosaminoglycan and decreased collagen content, as well as increased valve interstitial cell expression of Sox9, a transcription factor essential for normal ECM maturation during heart valve development. This study provides the first evidence that Tie1 is involved in modulation of late valve remodeling and suggests that an important Tie1-Sox9 signaling axis exists through which disturbed flows are converted by endocardial cells to paracrine Sox9 signals to modulate normal matrix remodeling of the aortic valve.

Proteomic Alterations Associated with Biomechanical Dysfunction are Early Processes in the Emilin1 Deficient Mouse Model of Aortic Valve Disease.

Aortic valve (AV) disease involves stiffening of the AV cusp with progression characterized by inflammation, fibrosis, and calcification. Here, we examine the relationship between biomechanical valve function and proteomic changes before and after the development of AV pathology in the Emilin1-/- mouse model of latent AV disease. Biomechanical studies were performed to quantify tissue stiffness at the macro (micropipette) and micro (atomic force microscopy (AFM)) levels. Micropipette studies showed that the Emilin1-/- AV annulus and cusp regions demonstrated increased stiffness only after the onset of AV disease. AFM studies showed that the Emilin1-/- cusp stiffens before the onset of AV disease and worsens with the onset of disease. Proteomes from AV cusps were investigated to identify protein functions, pathways, and interaction network alterations that occur with age- and genotype-related valve stiffening. Protein alterations due to Emilin1 deficiency, including changes in pathways and functions, preceded biomechanical aberrations, resulting in marked depletion of extracellular matrix (ECM) proteins interacting with TGFB1, including latent transforming growth factor beta 3 (LTBP3), fibulin 5 (FBLN5), and cartilage intermediate layer protein 1 (CILP1). This study identifies proteomic dysregulation is associated with biomechanical dysfunction as early pathogenic processes in the Emilin1-/- model of AV disease.

Site-specific associations of muscle thickness with bone mineral density in middle-aged and older men and women.

It is unknown whether age-related site-specific muscle loss is associated with areal bone mineral density (aBMD) in older adults. To examine the relationships between aBMD and whole-body muscle thickness distribution, 97 healthy adults (46 women and 51 men) aged 50-78 years volunteered. Total and appendicular lean soft tissue mass, aBMD of the lumbar spine (LS-aBMD) and femoral neck (FN-aBMD) were determined using dual-energy X-ray absorptiometry. Muscle thickness (MT) was measured by ultrasound at nine sites of the body (forearm, upper arm, trunk, upper leg, and lower leg). Relationships of each co-variate with aBMD were tested partialling out the effect of age. aBMD was not correlated with either MT of the trunk or anterior lower leg in either sex. In men, significant and relatively strong correlations were observed between anterior and posterior upper arms, posterior lower leg, and anterior upper leg MT and LS-aBMD or FN-aBMD. In women, significant correlations were observed between anterior and posterior upper legs, posterior lower leg, and anterior upper arm MT and FN-aBMD. LS-aBMD was only correlated with forearm and posterior upper leg MT in women. In conclusion, the site-specific association of MT and aBMD differs between sexes and may be associated with the participants' daily physical activity profile.

Notch1 Mutation Leads to Valvular Calcification Through Enhanced Myofibroblast Mechanotransduction.

OBJECTIVE: Calcific aortic valve disease (CAVD) is a significant cardiovascular disorder, and controversy exists as to whether it is primarily a dystrophic or osteogenic process in vivo. In this study, we sought to clarify the mechanism of CAVD by assessing a genetic mutation, Notch1 heterozygosity, which leads to CAVD with 100% penetrance in humans. APPROACH AND RESULTS: Murine immortalized Notch1(+/-) aortic valve interstitial cells (AVICs) were isolated and expanded in vitro. Molecular signaling of wild-type and Notch1(+/-) AVICs were compared to identify changes in pathways that have been linked to CAVD-transforming growth factor-ß1/bone morphogenetic protein, mitogen-activated protein kinase, and phosphoinositide 3-kinase/protein kinase B-and assessed for calcification potential. Additionally, AVIC mechanobiology was studied in a physiologically relevant, dynamic mechanical environment (10% cyclic strain) to investigate differences in responses between the cell types. We found that Notch1(+/-) AVICs resembled a myofibroblast-like phenotype expressing higher amounts of cadherin-11, a known mediator of dystrophic calcification, and decreased Runx2, a known osteogenic marker. We determined that cadherin-11 expression is regulated by Akt activity, and inhibition of Akt phosphorylation significantly reduced cadherin-11 expression. Moreover, in the presence of cyclic strain, Notch1(+/-) AVICs exhibited significantly upregulated phosphorylation of Akt at Ser473 and smooth muscle α-actin expression, indicative of a fully activated myofibroblast. Finally, these Notch1-mediated alterations led to enhanced dystrophic calcific nodule formation. CONCLUSIONS: This study presents novel insights in our understanding of Notch1-mediated CAVD by demonstrating that the mutation leads to AVICs that are fully activated myofibroblasts, resulting in dystrophic, but not osteogenic, calcification.

Cadherin-11 regulates cell-cell tension necessary for calcific nodule formation by valvular myofibroblasts.

OBJECTIVE: Dystrophic calcific nodule formation in vitro involves differentiation of aortic valve interstitial cells (AVICs) into a myofibroblast phenotype. Interestingly, inhibition of the kinase MAPK Erk kinase (MEK)1/2 prevents calcific nodule formation despite leading to myofibroblast activation of AVICs, indicating the presence of an additional mechanotransductive component required for calcific nodule morphogenesis. In this study, we assess the role of transforming growth factor ß1-induced cadherin-11 expression in calcific nodule formation. METHODS AND RESULTS: As shown previously, porcine AVICs treated with transforming growth factor ß1 before cyclic strain exhibit increased myofibroblast activation and significant calcific nodule formation. In addition to an increase in contractile myofibroblast markers, transforming growth factor ß1-treated AVICs exhibit significantly increased expression of cadherin-11. This expression is inhibited by the addition of U0126, a specific MEK1/2 inhibitor. The role of increased cadherin-11 is revealed through a wound assay, which demonstrates increased intercellular tension in transforming growth factor ß1-treated AVICs possessing cadherin-11. Furthermore, when small interfering RNA is used to knockdown cadherin-11, calcific nodule formation is abrogated, indicating that robust cell-cell connections are necessary in generating tension for calcific nodule morphogenesis. Finally, we demonstrate enrichment of cadherin-11 in human calcified leaflets. CONCLUSIONS: These results indicate the necessity of cadherin-11 for dystrophic calcific nodule formation, which proceeds through an Erk1/2-dependent pathway.

EMT-inducing biomaterials for heart valve engineering: taking cues from developmental biology.

Although artificial prostheses for diseased heart valves have been around for several decades, viable heart valve replacements have yet to be developed due to their complicated nature. The majority of research in heart valve replacement technology seeks to improve decellularization techniques for porcine valves or bovine pericardium as an effort to improve current clinically used valves. The drawback of clinically used valves is that they are nonviable and thus do not grow or remodel once implanted inside patients. This is particularly detrimental for pediatric patients, who will likely need several reoperations over the course of their lifetimes to implant larger valves as the patient grows. Due to this limitation, additional biomaterials, both synthetic and natural in origin, are also being investigated as novel scaffolds for tissue-engineered heart valves, specifically for the pediatric population. Here, we provide a brief overview of valves in clinical use as well as of the materials being investigated as novel tissue-engineered heart valve scaffolds. Additionally, we focus on natural-based biomaterials for promoting cell behavior that is indicative of the developmental biology process that occurs in the formation of heart valves in utero, such as epithelial-to-mesenchymal transition or transformation. By engineering materials that promote native developmental biology cues and signaling, while also providing mechanical integrity once implanted, a viable tissue-engineered heart valve may one day be realized. A viable tissue-engineered heart valve, capable of growing and remodeling actively inside a patient, could reduce risks and complications associated with current valve replacement options and improve overall quality of life in the thousands of patients who received such valves each year, particularly for children.

Sensing and modulation of invadopodia across a wide range of rigidities.

Recent studies have suggested that extracellular matrix rigidity regulates cancer invasiveness, including the formation of cellular invadopodial protrusions; however, the relevant mechanical range is unclear. Here, we used a combined analysis of tissue-derived model basement membrane (BM) and stromal matrices and synthetic materials to understand how substrate rigidity regulates invadopodia. Urinary bladder matrix-BM (UBM-BM) was found to be a rigid material with elastic moduli of 3-8 MPa, as measured by atomic force microscopy and low-strain tensile testing. Stromal elastic moduli were ∼6-fold lower, indicating a more compliant material. Using synthetic substrates that span kPa-GPa moduli, we found a peak of invadopodia-associated extracellular matrix degradation centered around 30 kPa, which also corresponded to a peak in invadopodia/cell. Surprisingly, we observed another peak in invadopodia numbers at 2 GPa as well as gene expression changes that indicate cellular sensing of very high moduli. Based on the measured elastic moduli of model stroma and BM, we expected to find more invadopodia formation on the stroma, and this was verified on the stromal versus BM side of UBM-BM. These data suggest that cells can sense a wide range of rigidities, up into the GPa range. Furthermore, there is an optimal rigidity range for invadopodia activity that may be limited by BM rigidity.

Comparison of the validity of anthropometric and bioelectric impedance equations to assess body composition in adolescent girls.

OBJECTIVE: The purpose of this study was to examine the validity of two anthropometric and four bioelectric impedance (BIA) equations to estimate body composition from dual-energy x-ray absorptiometry (DXA) in adolescent girls of various ethnicities. The rationale for this study was to develop a prediction equation for percent body fat in a multi-ethnic, representative sample of sixth to eighth grade girls. DESIGN: One-hundred and sixty-six girls (51 African-American, 45 non-Black Hispanic, 55 non-Hispanic Caucasian, 15 multi-ethnic) participated. Estimates of percent fat and fat-free mass (FFM) from six published BIA and anthropometric equations and the equation developed from this study were compared to body composition determined from DXA. An RJL Systems analyzer was used to measure BIA. Anthropometry included body weight, height, and triceps and calf skinfolds. RESULTS: Average (± SD) age, size and body composition was as follows: age, 12.1±1.2 yrs, body mass 52.7±15.9 kg, height, 154.6±8.1 cm; DXA percent fat, 27.9±10.4; fat mass (FM), 15.6±10.2 kg; and fat free mass (FFM) 35.7±6.8 kg. No ethnic differences were found in the relationships between estimated and DXA measured body composition, with the exception of the skinfold equation. The six equations explained on average 82% of the variance in percent fat, 94% of the variance in fat mass, and 88% in fat free mass. Bland-Altman analysis indicated that none of the equations performed satisfactorily in our sample. CONCLUSIONS: The BIA and anthropometric equations were significantly related to DXA body composition parameters, however none met the criteria for cross-validation.

Comparison of two bioelectrical impedance analysis instruments for determining body composition in adolescent girls.

The purpose of this study was to compare fat-free mass (FFM) and percent body fat determined by two bio-electrical impedance analysis (BIA) instruments against criterion estimates determined by dual-energy x-ray absorptiometry (DXA) in a multi-racial/ethnic sample of adolescent girls. BIA was assessed in 151 girls (n=51 African-American; n=45 Hispanic; n=55 Caucasian; age 12.2 +/- 1.2 yr) using the RJL Quantum II and the American Weights and Measures Body-Comp Scale (BCS). Percent body fat determined by BIA was significantly related to that determined by DXA (R(2)=0.87, SEE=2.8% for RJL vs DXA, P<0.0001; R(2)=0.71, SEE=4.4% for BCS vs DXA, P<0.0001). The agreement between DXA and BIA for FFM was also significant (R(2)=0.91, SEE=0.03 kg for RJL, P <0.0001; R(2)=0.79, SEE=0.04 kg for BCS, P <0.0001). The BCS overestimated FFM by 2.7 kg (P<0.0001) and underestimated percent body fat by over 4% (P<0.001). There were no differences in percent body fat between DXA and the RJL, and although the RJL significantly overestimated FFM, the absolute difference was <1 kg. Within each ethnic group, the RJL instrument more closely estimated FFM and percent body fat than did the BCS. Although both BIA instruments compared favorably with DXA, the RJL had better stability and accuracy than the BCS, for both the total sample and for the three ethnic groups. Considering its relatively low cost and minimal time required for technical training, BIA is a useful and appropriate technique for assessing body composition in adolescent girls.

Validation of bioelectrical impedance analysis (BIA) for estimation of body composition in Black, White and Hispanic adolescent girls.

AIM: Equations for estimating % fat mass (%BF) and fat-free mass (FFM) from bioelectrical impedance analysis (BIA) that work in adolescent girls from different racial/ethnic backgrounds are not available. We investigated whether race/ethnicity influences estimation of body composition in adolescent girls. PRINCIPAL PROCEDURES: Prediction equations were developed for estimating FFM and %BF from BIA in 166 girls, 10-15 years old, consisting of 51 Black (B), 45 non-Black Hispanic (H), 55 non-Hispanic White (W) and 15 mixed (M) race/ethnicity girls, using dual energy x-ray absorptiometry (DXA) as the criterion method. FINDINGS: Black girls had similar %BF compared to other groups, yet were heavier per unit of height according to body mass index (BMI: kg.m(-2)) due to significantly greater FFM. BIA resistance index, age, weight and race/ethnicity were all significant predictors of FFM (R(2) = 0.92, SEE = 1.81 kg). Standardized regression coefficients showed resistance index (0.63) and weight (0.34) were the most important predictors of FFM. Errors in %BF (~2%) and FFM (~1.0 kg) were greater when race/ethnicity was not included in the equation, particularly in Black girls. We conclude the BIA-composition relationship in adolescent girls is influenced by race, and consequently have developed new BIA equations for adolescent girls for predicting FFM and %BF.

Scaling VO(2) peak in obese and non-obese girls.

OBJECTIVE: The conventional ratio method (milliliters O(2) per mass) typically is used to express VO(2) peak. The goal of the current study was to compare VO(2) peak of obese girls with normal-weight girls by ratio and allometric scaling methods. RESEARCH METHODS AND PROCEDURES: We compared VO(2) peak by ratio and allometric methods in 46 obese and 47 normal-weight girls. Indirect calorimetry was used to measure VO(2) peak during either treadmill running or walking. Regression analysis was used to determine coefficients for mass and stature for each group with ANOVA used to compare data between groups. RESULTS: The obese girls were taller and had higher values of body fatness (p < or = 0.05). Absolute VO(2) peak (liters per minute) was similar between groups; however VO(2) peak relative to mass was 50% lower (p < or = 0.05) in the obese girls. When VO(2) peak (milliliters per minute per kilogram) and mass were correlated, r = -0.48 was found in the obese group. Allometric scaling of logarithmic transformed stature and mass reduced this to r = -0.002, thus eliminating the bias associated with the ratio method. Adjusting VO(2) peak allometrically scaled for mass, stature, and the combination of mass and stature reduced the difference between groups from 50% (ratio method) to 10% to 11% (p < or = 0.05) with higher values found in the normal-weight girls. DISCUSSION: These results demonstrate the bias associated with the ratio method when comparing VO(2) peak in obese girls with VO(2) peak in normal-weight girls. Allometric scaling eliminated the bias and thus may reflect a truer comparative response.

Impact of significant weight loss on maximal oxygen uptake in obese children and adolescents.

BACKGROUND: The prevalence of pediatric obesity has increased over the past few decades in all ethnic, gender, and age groups. The treatment of obesity, especially in children with moderate to severe conditions, is difficult. In this study, we examined the impact of significant weight loss as a result of participation in a multi-disciplinary weight management program on maximal oxygen uptake (VO2max) in obese children and adolescents. METHODS: Eleven obese children and adolescents (7 to 14 years of age; mean age, 12.3 +/- 1.9 years) were enrolled in a weight management program at the Children's Hospital of New Orleans. The treatment program included a high-protein, very low-calorie diet (VLCD; protein intake, 1.5 to 2.0 g/kg of ideal body weight per day; and 800 kcal/d). Diets were supplemented with extra fluid, minerals, and vitamins. All subjects attended weekly 2-hour clinic sessions. During these sessions, they received nutrition instruction, participated in a moderate-intensity, progressive exercise program, and learned behavior-modification techniques. Weight, height, body mass index ([BMI]; wt/ht2), and VO2max by indirect calorimetry were obtained at enrollment and at the end of 10 weeks of treatment. RESULTS: There was a significant decrease in body weight after 10 weeks. The BMI decreased significantly from 34.1 +/- 4.8 on entry to 29.4 +/- 3.5 (mean +/- SD; P < 0.0001). Despite the significant weight loss, VO2max increased significantly (P < 0.001) from entry (19.2 +/- 3.0 mL/kg/min) to completion of 10 weeks (22.4 +/- 5.8 mL/kg/min). However, absolute VO2max L/min was unchanged. CONCLUSIONS: We conclude that relative VO2max mL/kg/min is significantly improved in obese youth after significant weight loss with a VLCD and moderate-intensity, progressive exercise. However, because absolute VO2max L/min was unchanged, this improvement seems to result from the reduction in total body weight as opposed to the effect of the moderate-intensity exercise intervention.

Sex differences in pain indices, exercise, and use of analgesics.

To understand better reported sex differences in sensitivity to pain, this study examined daily pain frequency and intensity, use of analgesics, physical activity, and both subjective and physiological response to acute pain in 18 men and 24 women, healthy people who provided information about their daily pain symptoms and physical activity before completing a cold pressor task. Compared to men, women reported more frequent and intense pain symptoms, as well as more frequent use of analgesics and lower physical activity. Women evinced higher physiological arousal during the cold pressor task but similar subjective pain. The findings highlight the different ways men and women cope with pain and the effect on their responses to acute pain.

Effects of familial pain models on daily pain indices and performance during the cold pressor task.

To understand better the role of pain history in current response to pain episodes, this research examined pain-related indices from the patient's family of origin and their relationships to the patient's coping with acute pain. Participants were 42 healthy men and women who provided information about their own and their family's pain history and then were administered a cold pressor task. High frequency of family pain modeling was associated with higher frequency of current pain episodes, more types of pain, greater intensity, and also lower physiological arousal and subjective pain ratings during the cold pressor. The findings underscore the relationships between familial pain modeling and current pain-related functioning.

The impact of significant weight loss on resting energy expenditure in obese youth.

BACKGROUND: The prevalence of obesity in American youth is increasing and treating the condition is difficult. METHODS: We have developed a multidisciplinary weight-reduction program that includes a very low calorie diet followed by a hypocaloric diet, exercise, and behavior modification. Based on data collected at baseline and at the end of the acute intervention phase (10 weeks), we assessed the impact of the weight loss that resulted from participation in this weight reduction program on the resting energy expenditure and body composition of obese children and adolescents. RESULTS: There was a significant decrease in body weight and body fat as assessed by weight determinations and skin-fold measurements after 10 weeks. The body mass index decreased significantly from 33.8 on entry to 29.6 (P < 0.0001). Despite the significant weight loss, resting energy expenditure and lean body mass remained constant from entry until the completion of the acute phase. CONCLUSION: We conclude that a multidisciplinary weight-reduction program that combines a very low calorie diet followed by a balanced hypocaloric diet, with a moderate-intensity progressive exercise program and behavior modification is an effective means for weight-reduction in obese children and adolescents. Furthermore, fat mass is significantly reduced while lean body mass and resting energy expenditure are unaltered.

The health benefits of physical activity in children and adolescents: implications for chronic disease prevention.

UNLABELLED: Clinical, epidemiological and basic research evidence clearly supports the inclusion of regular physical activity as a tool for the prevention of chronic disease and the enhancement of overall health. In children, activities of a moderate intensity may enhance overall health, and assist in preventing chronic disease in at-risk youth. The numerous health benefits of regular exercise are dependent on the type, intensity and volume of activity pursued by the individual. These benefits include reduction of low density lipoproteins while increasing high density lipoprotein; improvement of glucose metabolism in patients with type II diabetes; improved strength, self esteem and body image; and reduction in the occurrence of back injuries. In addition, a progressive, moderate-intensity exercise program will not adversely effect the immune system and may have a beneficial effect on the interleukin-2/natural killer cell system. Furthermore, by decreasing sedentary behaviors and, thus, increasing daily physical activity, individuals may experience many stress-reducing benefits, which may enhance the immune system. CONCLUSION: Moderate intensity exercise of a non-structured nature seems to facilitate most of the disease prevention goals and health promoting benefits. With new guidelines promoting a less intense and more time-efficient approach to regular physical activity, it is hoped that an upward trend in the physical activity patterns, and specifically children at risk for chronic disease, will develop in the near future.

Effects of frequency of pain report on subjective pain ratings of the cold pressor task.

Differences in methodology among studies using the cold pressor task have affected the level of pain reported by subjects. This study was designed to assess the effects of varying frequency of self-report on intensity of subjective pain ratings. In a sample of 108 subjects, significant differences in pain ratings were found between subjects who rated their pain at 50-sec. intervals and groups who rated at lower or higher frequencies. Analysis indicated that the frequency of reporting pain may influence the coping strategies used by patients with pain and should be considered carefully by researchers.

Host preference of mosquitoes in Bernalillo County, New Mexico.

Host preference of mosquitoes was determined using animal-baited traps. Hosts used in the study were cattle, chickens, dogs, and horses. Ten mosquito species representing 4 genera were collected from the animal-baited traps. Aedes vexans, Aedes dorsalis, Culex quinquefasciatus. Culex tarsalis, and Culiseta inornata were used as indicator species for data analysis. Greater numbers of Ae. vexans, Ae. dorsalis, and Cs. inornata were collected from cattle and horses than from chickens or dogs. In addition, engorgement rates were higher on mammals than on chickens. Engorgement and attraction data for Cx. quinquefasciatus suggested a preference for chickens and dogs over cattle and horses. A slight preference for chickens and dogs was seen with Cx. tarsalis, but the degree of host preference of Cx. tarsalis was less than that in either Ae. vexans or Cx. quinquefasciatus.

Heart rate response during handball singles match-play and selected physical fitness components of experienced male handball players.

Limited information is available concerning the exercise response during handball (HB) singles match-play. Also, few studies exist that have examined VO2 peak and body composition of HB players. The purpose of this study was to examine the heart rate (HR) response during match play and peak physiologic responses and relative fat in twelve experienced HB players. Peak physiologic responses were measured during treadmill running and body composition was assessed via hydrodensiotometry. During HB match-play, HR was measured and stored every five seconds using a Polar Vantage XL heart watch. Physical characteristics and peak physiologic responses included the following: Age (yrs) 47.2; BW (kg) 78.0; height (cm) 178.9; % fat 18.9; VO2 peak (ml.kg-1.min-1) 48.0; RER peak 1.03; HR peak (bpm) 183.1 and lactic acid peak (mmol.l-1) 10.3. During HB match-play, HR averaged 85% of peak during one hour of play. Moreover, 67% of match-play time, HR was > 80% of peak. When HR responses were examined over one hour of match-play (twelve, five minute blocks) only the first five minutes were significantly different (lower) than the other 55 minutes. The exercise intensity and the relatively stable HR response observed during HB suggests that this activity appears to be appropriate for meeting the American College of Sports Medicine guidelines to develop and maintain cardiorespiratory fitness.