Graded Treadmill Test Research Articles

Effects of Maximal Effort Running on Special Agents' Loaded and Unloaded Drop Jump Performance and Mechanics.

The purpose was to investigate the effect of load and fatigue on landing forces and mechanics. Thirteen Department of State special agents first completed drop jump testing, a maximal treadmill test, and another round of drop jump testing. During drop jump testing, agents performed 3 maximal effort drop jumps from 30 cm with body mass only (unloaded) or a 15 kg weight-vest (loaded). A force plate was used to collect force–time data, while two laptops were placed 3 m from the force plate from frontal and sagittal planes. Two-way analyses of variance were used to analyze the effect of load and fatigue on landing forces and Landing Error Scoring System (LESS) with alpha of p < 0.05. Dropping from 30 cm with 15 kg resulted in greater landing impulse, which was driven by increases in contact time. The loaded condition also resulted in lower jump height and reactive strength indexes. After the maximal graded treadmill test there were no further changes in drop jump ground reaction forces or performance. However, relative aerobic capacity was related to impulse changes following the treadmill test in unloaded (R2 = 0.41; p = 0.018) and loaded conditions (R2 = 0.32; p = 0.044). External loads of 15 kg increased impulse and contact time and resultantly decreased drop jump height and reactive strength indexes. It is encouraged that training protocols be aimed to concomitantly improve aerobic capacity and lower body power. Plyometric training with progressive overloading using external loads may be helpful, but further research is warranted.

Comparison Of Adult Omni Rate Of Perceived Exertion With Heart Rate During Aerobic Field Test

INTRODUCTION: Adult OMNI Rate of Perceived Exertion (OMNI RPE) has been widely validated in laboratory settings with physiological variables across gender, race, adults, children and health status. However, comparative studies on adults with physiological variables in field settings are limited. PURPOSE: To compare OMNI RPE with heart rate (HR) in Progressive Aerobic Cardiovascular Endurance Run (PACER) test for adults. METHODS: Fifteen healthy male participants ((age: 23.47 ± 1.56 yrs, height: 1.73 ± 0.03 m, weight: 67.91 ± 5.8 kg, body fat percent (%BF): 13.6 ± 4.51%)) were recruited. It consisted of two sessions conducted at least 24 hours apart between each session. The first session involved an OMNI RPE familiarization session with standardized instructions and a discontinuous running submaximal graded exercise treadmill test (GXT). The GXT was conducted at a 4-minute per stage (run/rest) protocol and terminated with HR at 70% maximum HR (HRmax) (HRmax = 220 - age). It started at 6 km/h and increased 0.5 km/h per stage. HR and OMNI RPE values were recorded at the last minute per stage. The second session was a 20 m PACER test which terminated when participants failed to keep up with the pace twice or till volitional exhaustion. HR and OMNI RPE values were recorded at alternate stages. HR was measured with a HR transmitter in GXT and PACER test. Participants gestured their OMNI RPE score when asked “on a scale of 0 to 10, can you tell me how tired are you feeling overall” in GXT and PACER test. RESULTS: A significant positive correlation was observed between average HR and OMNI RPE in the PACER test (HR: 173.29 ± 17.13beats•min-1, OMNI RPE: 5.34 ± 3.24, r = 0.90, p = 0.00) and GXT (HR: 134.67 ± 23.10beats•min-1, OMNI RPE: 3.92 ± 2.20, r = 0.81, p = 0.00). A significant linear regression analysis indicated that OMNI RPE responses distributed a positive linear function to HR in PACER test (R2 = 0.51, r = 0.71, p = 0.001, SEE: 16.36) and GXT (R2 = 0.65, r = 0.81, p = 0.000, SEE: 13.67). CONCLUSIONS: Regression analysis indicated a positive linear relationship between OMNI RPE and HR during PACER test and GXT. OMNI RPE and HR results from GXT and PACER test were similar and increased progressively as exercise intensity increased. Thus, OMNI RPE can be used instead of using HR monitors to monitor HR in field exercises for self-regulation of exercise intensity.

Low Cardiorespiratory Fitness Is Associated With Pericardial, Visceral, And Hepatic Adipose Tissue Accumulation In CARDIA

PURPOSE: This study quantified the association between cardiorespiratory fitness (CRF) and organ-related fat accumulation in 2028 CARDIA participants. METHODS: Fat depots were measured in 2010-11 (ages 43-55) by CT scan, including pericardial (PAT), visceral (VAT) and subcutaneous (SAT) adipose tissue, and also hepatic lipid infiltration, or steatosis (HS). CRF was assessed by graded treadmill test duration in 2005-06, along with covariates age, sex, race, parity in women, education, blood pressure and lipids, smoking status, alcohol intake, dietary fat and sugar intake, insulin resistance (HOMA-IR), 5-year weight gain, physical activity, and BMI or DXA %fat. Exclusion criteria included diabetes, diabetes medication, and pregnancy. Extreme outliers were removed. Analysis of variance was used to determine mean differences in sex-specific CRF quartiles (means ± SD). Sequential modeling was used to test associations between CRF and central fat volume. RESULTS: Quartile differences are displayed in table. No differences between Q1 and Q4 were observed for age (45.3 ± 3.3 vs 45.1 ± 3.8), caloric intake (2352 ± 1072 vs 2426 ± 1207), or dietary fat intake (94.7 ± 57.6 vs 100.6 ± 60.3). Lower CRF was significantly associated with higher fat accumulation in each fat depot, independent of all covariates examined [values are Beta ± SE: -.056 ± .01 (VAT); -.114 ± .02 (SAT); -.027 ± .01 (PAT); .008 ± .002 (HS); p < .001 for all]. When the other fat depots were added to the model, CRF remained associated with VAT, SAT, and PAT [-.045 ± .01 (VAT); -.114 ± .02 (SAT); and -.025 ± .004 (PAT); p < .0001], but not with HS (.003 ± .002, p = .117). CONCLUSIONS: Lower CRF is associated with higher organ-related adipose accumulation. This association is independent of overall adiposity, diet, insulin resistance, physical activity, and circulating lipids. Moreover, the fat accumulation in each region, except for HS, has an association with CRF that is independent from fat accumulation in other regions.

Maximal isometric strength indices are associated with the oxygen cost of walking and running in recreationally active men and women

ABSTRACT This study assessed the associations of maximal isometric strength and movement economy in 126 recreationally active men and women. Oxygen consumption was assessed through a graded treadmill test with 4-minute increments (4–12 km∙h−1). Maximal isometric leg extensor, leg flexor and handgrip strength were assessed by isometric dynamometry. Models of best fit for gross oxygen cost and gross caloric unit cost were observed across the majority of velocities when the leg extensor/flexor strength ratio and handgrip strength were combined (R2 = 0.207–0.525 and R2 = 0.152–0.475, respectively). Additionally, the oxygen cost differed statistically for the majority of velocities when participants were split by the median of leg extensor strength (12.3–26.3 ml∙kg−1∙km−1, p < 0.05) and the average of all strength variables (13.9–30.3 ml∙kg−1∙km−1, p < 0.05). Our data underline the importance of maintaining maximal strength in order to perform activities with low to moderate oxygen demands.

Criterion Validity of the Older-adults 2-minute Step Test in Community-dwelling Middle-aged Adults

ABSTRACT The 2-minute step test (2MST) requires minimal resources and is valid in adults older than 60 years. Here we investigate if the 2MST can be used to estimate peak oxygen consumption (VO2peak) in healthy middle-aged adults (40–59 years old). Thirty-six participants completed the 2MST and a maximal graded treadmill test with breath-by-breath gas analysis. Outcome measures included the number of steps completed in the 2MST, VO2peak (ml/kg/min), waist circumference (cm), resting blood pressure (mmHg) and body mass index (kg/m2). Data were analyzed using Pearson correlation coefficients and multivariate linear regression analyses. There was a moderate relationship between 2MST peak steps completed and VO2peak (r = .54, p = .001). The 2MST model, including 2MST peak steps, height and waist circumference, predicted VO2peak with r = .80 (p < .001). The 2MST may be a good predictor of VO2peak in healthy middle-aged adults, and may be suitable for primary health-care settings and large-scale epidemiological studies. Trial registration: Australian New Zealand Clinical Trials Registry (ANZCTR): ACTRN12617000091303, http://www.ANZCTR.org.au/ACTRN12617000091303.aspx, date registered: 17 January 2017.

Effectiveness and Utilization of Cardiac Rehabilitation Among People With CKD

IntroductionCardiac rehabilitation (CR) is a proven therapy for reducing cardiovascular death and hospitalization. Whether CR participation is associated with improved outcomes in patients with chronic kidney disease (CKD) is unknown.MethodsWe obtained data on all adult patients in Calgary, Alberta, Canada with angiographically proven coronary artery disease from 1996 to 2016 referred to CR from The Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease and TotalCardiology Rehabilitation. An estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m2 or kidney replacement therapy defined CKD. Predictors of CR use were estimated with multinomial logistic regression. The association between starting versus not starting and completion versus noncompletion of CR and clinical outcomes were estimated using multivariable Cox proportional hazards models.ResultsOf 23,215 patients referred to CR, 12,084 were eligible for inclusion. Participants with CKD (N = 1322) were older, had more comorbidity, lower exercise capacity on graded treadmill testing, and took longer to be referred and to start CR than those without CKD. CKD predicted not starting CR: odds ratio 0.73 (95% confidence interval [CI] 0.64–0.83). Over a median 1 year follow-up, there were 146 deaths, 40 (0.3%) from CKD and 106 (1.0%) not from CKD. Similar to those without CKD, the risk of death was lower in CR completers (hazard ratio [HR] 0.24 [95% CI 0.06–0.91) and starters (HR 0.56 [95% CI 0.29– 1.10]) with CKD.ConclusionCR participation was associated with comparable benefits in people with moderate CKD as those without who survived to CR. Lower rates of CR attendance in this high-risk population suggest that strategies to increase CR utilization are needed.

Separate and combined relationships for cardiorespiratory fitness and muscular strength with visceral fat and insulin sensitivity in adolescents with obesity.

We examined the separate and combined associations for cardiorespiratory fitness (CRF) and muscular strength (MS) with total and regional fat, and insulin sensitivity (IS) in 204 adolescents (BMI ≥85th percentile, 12-18 years) at UPMC Children's Hospital of Pittsburgh. CRF was measured by maximum oxygen consumption during a graded treadmill test. MS was quantified by combining 1-repetition maximum test for the leg and bench press. Participants were stratified as having either high or low CRF and MS based on sex-specific median split. Both high CRF and high MS groups had lower (P < 0.05) total fat after adjustment for sex, Tanner stage and ethnicity than the low CRF and MS groups (Difference: 6.6, 2.6-9.6% and 5.4, 2.4-8.3%, respectively). High CRF, but not high MS, had lower visceral (67.5 versus 77.9 cm2, P < 0.01) and intermuscular fat (3.6 versus 4.0 kg, P = 0.01) than the low CRF groups. Differences by CRF remained significant after adjustment for MS. High CRF, but not high MS, was associated (P < 0.05) with lower fasting glucose and higher IS after accounting for sex, Tanner stage and ethnicity than the low CRF group, and high CRF remained associated with these markers after adjustment for MS. High CRF is associated with lower total and regional fat, and higher IS after adjustment for MS. Novelty: CRF is associated with lower total fat, visceral and intermuscular fat, and higher insulin sensitivity adjusting for muscular strength. Muscular strength is not associated with regional body fat and insulin sensitivity after accounting for CRF.

Abstract 14802: Relation of Non-exercise Walking Activity With Exercise Performance in Patients With Peripheral Artery Disease

Introduction: Structured exercise programs in home settings are beneficial for patients with peripheral artery disease (PAD). However, the impact of lower levels of walking activity accumulated separately from formal home exercise in PAD is unclear. The aim of this study was to determine the relation of non-exercise walking (NEW) activity with exercise performance in PAD. Methods: This was a post-hoc analysis from twenty patients with PAD enrolled in a 12-week structured home-based walking exercise program using diaries and accelerometry. Formal exercise sessions (3 sessions·week -1 ) were detected using patient-reported diary entries that corresponded with accelerometer step data. NEW activity was characterized as steps completed over five days each week, excluding steps during formal exercise sessions. The primary outcome for the intent-to-treat analysis was peak walking time (PWT) assessed on a graded treadmill. Secondary outcomes were claudication onset time (COT) from the graded treadmill test and maximal distance achieved during the six-minute walk test (6MWT). Pearson correlations evaluated the relation between NEW activity (step·week -1 ) and exercise performance outcomes using intensity (step·week -1 ) and duration (min·week -1 ) from formal exercise sessions as covariates. Results: NEW activity demonstrated a strong, positive correlation with change in PWT (r=0.50, p=0.04) when controlling for exercise intensity and duration during the 12-week intervention. Other exercise performance outcomes were not significantly related to NEW activity (COT: r=0.14; 6MWT maximal distance: r=0.27). Conclusions: A positive association was demonstrated between NEW activity and the primary outcome of PWT following 12 weeks of structured home-based walking exercise. Interventions to improve physical activity outside of formal exercise sessions may be beneficial for patients with PAD.

No Difference In Heart Rate Recovery During Graded Treadmill Testing In Patients With And Without Nonalcoholic Fatty Liver Disease (NAFLD)

Cardiac Mortality is the most common cause of death for nonalcoholic fatty liver disease (NAFLD), which is linked to physical inactivity and obesity. PURPOSE: To determine whether individuals with NAFLD show heart rate recovery impairment (iHRR is≤12 beats per minute at 1 minute post-exercise, an independent predictor of mortality) compared to non-NAFLD participants following graded treadmill testing (GTT) to volitional exhaustion. METHODS: Non-pharmacological clinical research participants with and without NAFLD were included. All performed symptom-limited, Modified Bruce GTT. Gas exchange captured cardiorespiratory variables and impedance cardiometry assessed heart rate, stroke volume, and cardiac output (CO) continuously during rest, testing, and recovery. Participants completed nutrition, activity, and fatigue questionnaires. Linear regression assessed effects of covariates on HRR. RESULTS: 86 participants (48.8% Male, 62.8% Caucasian, 65.8% NAFLD/NASH, Age 48 ± 13.6 years) were included for analysis. T-test comparisons showed individuals with NAFLD to be older (52 vs 41.4 years, p=.001), have higher body mass index (31.2 vs 28.4 kg/m 2 , p=.007), and increased body fat percentage, (34.1% vs 28.6%, p=.006) but showed no differences for resting pulse, blood pressure, gender, or ethnicity. Per GTT, individuals with NAFLD had reduced oxygen consumption at anaerobic threshold (AT) (12.3 vs 15.6 mL/kg/min) and peak exertion (23.1 vs 31.2 mL/kg/min, p<.001) compared to non-NAFLD. The NAFLD cohort also reported reduced maximal and average activity scores compared to the non-NAFLD group (MAS 89.8 vs 81.4, p=.001; AAS 88.1 vs 77.6, p<.001). No group differences were found for iHRR presence or continuous HRR measure. Stepwise linear regression showed peak CO (B=0.317, p=.041) and MAS (B=.348, p=.025) to be significant predictors of HRR for all participants (R 2 =.261). CONCLUSIONS: No HRR post exercise differences were found between NAFLD and non-NAFLD individuals. Increased CO and self-reported exercise capacity may indicate lower probability of impaired HRR. AAS and MAS were reduced in the NAFLD group, which may reflect reduced aerobic capacity at peak performance and AT. NAFLD individuals may benefit from exercise participation encouragement to improve tolerance of physical activity.

Evaluation Of Maximal Oxygen Uptake Using Verification Phases Of Different Intensities Across Fitness Levels

Confirmation of maximal oxygen consumption (V˙O2max) has relevance in both clinical and exercise settings. Though there are criteria in place to confirm V˙O2max has been attained, they are inconsistently achieved. For example, a plateau in V˙O2 with a corresponding increase in workload is often absent, and other criteria such as a respiratory exchange ratio (RER) ≥1.15 or heart rate (HR) within 10 beats per min (bpm) of age predicted maximum can result in an inaccurate estimate of V˙O2max. Due to these shortcomings, some researchers have suggested the use of a verification phase (VP) to confirm the attainment of V˙O2max. PURPOSE: Therefore, this study aimed to provide further evidence for the need to use a VP with V˙O2max testing protocols in populations of different fitness levels. METHODS: 49 participants (M: 27, F: 22; 21.9±2.6 y, 24.3±2.8 kg·m2) had their V˙O2 and HR measured during three maximal graded treadmill tests with each test followed by a VP of differing intensity (85%, 95%, 105% final workload). Participants were divided into groups based on their V˙O2max using norms adapted from American College of Sports Medicine (ACSM) V˙O2max guidelines (poor, fair, good, excellent) resulting in 7, 19, 18, and 5 participants respectively. V˙O2max from the graded treadmill test was confirmed with the VP and/or an additional test if the highest V˙O2 value achieved was no more than 2 x typical error (TE: 1.9 to 3.7 mL·kg-1·min-1 across groups). RESULTS: Plateau was achieved on 43/147 tests (29%), RER ≥ 1.15 was achieved on 104/147 tests (71%), HR within 10 bpm of age-predicted max was achieved on 83/147 tests (56%), and volitional fatigue was reached on 147/147 tests (100%). The highest V˙O2 value attained on the initial V˙O2max test was not different than either value attained following the VP at 95 or 105% of final V˙O2max test workload or a second repeat test on a separate day (P>0.211). The 85% VP V˙O2 value was lower than the initial V˙O2max test value (P<0.001). CONCLUSION: While traditional criteria to confirm the attainment of V˙O2max were inconsistently achieved, the use of a VP (at 95 or 105%) or a subsequent repeat test on a separate day were able to confirm the V˙O2max value attained. Our data also suggests exercise studies employing only a single V˙O2max test should consider these inconsistencies across a range of fitness levels.

Physiologic Evaluation Of A Collegiate Mascot During Football Games And Related Activities

PURPOSE: Our purpose was to collect collegiate mascot pilot data to determine physiological HR responses during two football games and pregame-related activities. METHODS: A physiological tracking system was used to evaluate HR and movement from individuals (N=7 [1 female]; avg ht=1.82m, wt=75.6kg) who performed mascot activities “in suit” (weighing ~14kg) before and during two NCAA Division I University football games. Both games were played at night under moderate ambient conditions (temp=22-14 °C, rh=64%, wind speed=4 mph). Prior to the study, individuals’ HRmax values were determined during graded treadmill tests performed to volitional exhaustion. Variables analyzed during the games were time in suit, time in pre-established HR zones [including HRzone1 (50-59%HRmax), HRzone2 (60-69%HRmax), HRzone3 (70-79%HRmax), HRzone4 (80-90%HRmax), and HRzone5 (>90%HRmax)], and distance covered per minute. Differences in time per HRzone were evaluated using 95% confidence intervals. Differences in average HR between pre-game and game conditions were evaluated via a t-test. RESULTS: Sessions in suit lasted 43.5±10.5 min, and distance traveled was 47±22 m/min. HR averaged 82±8% of HRmax, with over half the time spent in HRzone4 (34±20%; p<0.05) and HRzone5 (23±27%), with only 2±2% spent in HRzone1. HR values were significantly lower during pregame (74±4%HRmax) compared to game (85±6%HRmax) activities (p<0.001). CONCLUSIONS: The mascot suit environment posed significant physiological strain on the wearer, despite relatively little activity or movement performed per session.

IN-GAME PHYSIOLOGIC RESPONSES OF A DIVISION I COLLEGIATE MASCOT COMPARED TO VARSITY SOCCER ATHLETES

The physiologic responses collegiate athletes experience during practice/competition are reasonably well understood; however, an important yet understudied group who also exerts substantial effort during sporting events are team mascots. Mascots typically wear heavy suits/uniforms that create an environment not conducive to effective temperature regulation, thus putting the wearer under high physiologic stress. Although physiologic responses experienced by collegiate athletes and mascots during athletic competitions have been studied previously, it is unknown how these responses compare with one another. PURPOSE: To compare in-game heart rate (HR) responses and accelerometer data of a collegiate mascot with those of collegiate soccer athletes. METHODS: A physiological tracking system was used to evaluate HR and movement from three groups: a mascot while “in suit” [N=7 (1 female)] during a football game, and players in the first half of a varsity men’s (N=9) and women’s (N=9)] soccer game, separately. All games were played under similar ambient conditions (avg 21°C, 60% rh, 5 mph wind). Prior to the study, individuals’ HRmax values were determined during graded treadmill tests performed to volitional exhaustion or an on-field intermittent recovery test. Variables analyzed were time ”in suit”/on the field, distance traveled (meters/min), and percent of time in pre-established HR zones [HRzone1 (50-59%HRmax), HRzone2 (60-69%HRmax), HRzone3 (70-79%HRmax), HRzone4 (80-90%HRmax), and HRzone5 (>90%HRmax)]. Differences between groups were evaluated via a one-way ANOVA. RESULTS: There were no differences between groups for time spent “in suit”/on the field (~47 min); however there was a significant difference between groups for distance traveled (p<0.001), with the mascot traveling less distance (35±6 m/min) than the soccer players (men, 115±25 m/min, women, 107±4 m/min). All three groups spent over 90% of time “in-suit”/on the field in HRzones 3, 4 or 5, and 75% of time in HRzone 4 or 5. There were no significant differences between groups for time spent in various HRzones. CONCLUSION: The mascot suit environment created a physiological strain on the wearer similar to that of a varsity collegiate soccer athlete, despite much less movement performed per session.

Short interval or continuous training programs to improve walking distance for intermittent claudication: Pilot study.

Supervised exercise training is part of first-line therapies for intermittent claudication. Short periods of intensive treadmill training have been found efficient; however, the optimal modalities remain to be determined, especially interval training with active recovery (ITAR). In this prospective assessor-blinded single-centre pilot study, we assessed the feasibility of a randomised controlled trial comparing parallel 4-week intensive rehabilitation programs comprising treadmill training performed as ITAR or conventional training with constant slope and speed interspersed with rest periods (CT). A total of 38 in- or out-patients were randomised to the ITAR or CT program for 5 days/week for 4weeks. The primary outcome was change in maximum walking distance measured on a graded treadmill before and after the program. Adherence was high. All training sessions were completed in the ITAR program and only a few were not completed in the CT program (median 100% [Q1-Q3 96-100]). Tolerance was excellent (no adverse events). VO2peak was low in both groups, corresponding to moderate to severe exercise intolerance. The 2 groups did not differ in the primary outcome (median ITAR vs CT 480 [135-715] vs 315m [0-710]; p=0.62) or other walking distances (constant speed and gradient treadmill test). For all 38 participants, both programs greatly increased maximum walking distance in the graded treadmill test: median 415 [240-650] to 995m [410-1490], with a large effect size (p<10-4). A 4-week intensive rehabilitation program with ITAR or CT for intermittent claudication showed high adherence, was well tolerated, and improved walking distance as much as that reported for longer conventional programs. These findings prompt the design of a larger multicenter randomised controlled trial. NCT01734603.

Impact of Immune Function on Aerobic Capacity in Rats

BackgroundThe use of immunocompromised animals has been indispensable in cancer and immunology research. The use of exercise with these models in these areas of research has increased dramatically over the past decade, with little to no evidence of how immune modification of strains of animals is impacting exercise capacity and/or responses to training. This data is critical for extrapolation to exercise recommendations in humans as the majority of cancer patients do not present with primary immunodeficiency diseases. Recently, observations of lower skeletal muscle oxidative capacity between RNU (NIH Nude, immunocompromised) and Copenhagen rats (immunocompetent) have been speculated to result from possible differences between immune function in animals. The purpose of this study was to determine if there are differences in maximal aerobic capacity, through assessment of V̇o2max, between immune‐competent and ‐compromised animals of the same strain. We tested the hypothesis that immunocompromised animals would have a lower aerobic capacity than their immunocompetent counterparts.MethodsRNU 316 (NU−/−, T‐cell deficient; n=10) and RNU 118 (NU+/−, no deficiency; n=10) male rats (~4 months old) were obtained from Charles River. Both groups were acclimated to motorized treadmill running at varying speeds (20–40 m/min) for 3–5 sessions before beginning V̇o2max assessment. V̇o2max graded treadmill testing consisted of a 2‐minute warm‐up at 25 m/min at a 5% incline followed by 2 minutes at 35 m/min, and subsequent increases in speed of 5 m/min every minute after until a plateau was seen in oxygen consumption with increased speed, or test termination was required for safety of the animal. Tests were repeated a minimum of two times (3 maximally) per animal to verify maximum values were achieved.ResultsThere were no significant differences in body mass (NU−, 347±12 g, NU+, 321±8 g; p=0.17). V̇o2max was lower in NU− vs NU+ animals (80.0±1.5 vs. 88.4±1.9 ml·min−1·kg−1; p&lt;0.01). There was a significant difference in respiratory exchange ratio (RER) at V̇o2max (NU−, 1.05±0.01 vs. NU+, 0.98±0.01; p&lt;0.05), but no difference in CO2 production (NU−, 83.7±1.3 vs. NU+, 86.7±1.5 ml·min−1·kg−1; p&gt;0.05).ConclusionThis study suggests that immunocompromised animals have a decreased aerobic capacity compared to immunocompetent counterparts. This should be considered when both designing exercise interventions in immunedeficient/compromised animals as well as interpretations derived from such studies.Support or Funding InformationNIH HL137156‐01A1ACS RSG‐14‐150‐01‐CCE

Why to evaluate the functional capacity in PAD patients?

In patients with peripheral arterial disease (PAD), the ability to perform physical exercise is an essential and most important indicator of a patient's health and quality of life. In many cases, there exists a discrepancy between lower extremity blood flow, the extent of arterial occlusion shown by morphological investigation and functional impairment. Reversal of lower extremity arterial obstruction with revascularization does not always reverse functional impairment of diseased leg. Further, training exercise and drug treatment can improve functional performance although they are not associated with an improvement in arterial obstruction. Therefore, the determination of functional impairment and its recovery after different therapeutic procedures should be determined using objective tests. The most frequently used functional tests are treadmill exercise testing and a 6-minute walk test. The constant load test, in which results are expressed as a walked distance, does not always permit an accurate assessment of the full range of functional impairment of PAD patients. Recently, as a substitute for a constant-load test, the graded treadmill test is used. With this test, it is possible to identify those individuals with exercise limitations who are not caused only by deterioration of the blood flow of lower limbs. The 6-minute walk test is simple to perform and requires minimal equipment. However, the correlation between the 6-minute walk test and the graded treadmill test is relatively weak, indicating that peak performance on a graded treadmill may reflect different pathophysiological mechanisms of limitations. In conclusion: for the determination of limitations of mobility and quality of life in patients with PAD, objective measures of functional impairment are needed. The determination of functional capacity is related to the quality of life and is a useful tool for investigation of the success of revascularization of peripheral arteries and conservative treatment.

Seasonal changes in wildland firefighter fitness and body composition

Hiking with a pack is the highest-intensity task that wildland firefighters (WLFFs) perform during sustained activities related to wildland fire suppression. Firefighters perform this and other tasks together as a crew; this provides a unique model to evaluate select physical and physiological changes in members of working crews over a fire season during extended operations. The objective of this study was to evaluate changes in peak aerobic fitness (VO2peak), sustainable aerobic fitness at the ventilatory threshold (VO2vt) and body composition over a 5-month wildland fire season. WLFFs from four crews (55 males, 10 females) participated in a maximal graded exercise treadmill test and body composition evaluation pre- and post season. VO2peak values and variance did not change across the fire season (pre=3.96±0.65, post=3.96±0.69Lmin−1, not significant). VO2vt average decreased slightly while variance decreased greatly within each crew (pre=37.5±7.0, post=35.4±2.3mLkg−1 min−1, P&amp;lt;0.05). There was an improvement in VO2vt in initially less-fit WLFFs and a VO2vt decrease in initially more-fit WLFFs. WLFFs lost fat mass (−1.56±−1.06kg, P&amp;lt;0.01) and fat-free mass (−0.38±−1.24kg, P&amp;lt;0.05). Post-season VO2vt values were the same as the higher range of the documented metabolic cost of uphill load carriage and reveal a unique group adaptation to extended physical demands.

Exercise Intensity during 6-Minute Walk Test in Patients with Peripheral Artery Disease.

ResumoFundamento a caminhada não supervisionada em solo tem sido indicada para pacientes com doença arterial periférica (DAP) sintomática. No entanto, a magnitude do esforço exigido por essa atividade e as características dos pacientes que a praticam com mais intensidade não estão claras.Objetivos determinar se a caminhada em solo excede o limiar ventilatório (LV), um reconhecido marcador de intensidade de exercício, em pacientes com DAP sintomática.Métodos Foram recrutados 70 pacientes (61,4% do sexo masculino e com idade entre 40 e 85 anos) com DAP sintomática. Os pacientes realizaram um teste ergométrico em esteira para definir o LV. Em seguida, foram submetidos ao teste de caminhada de 6 minutos para determinar o alcance do LV durante deambulação no solo. Realizou-se regressão logística múltipla para identificar preditores de LV durante o teste de caminhada de 6 minutos, e o valor de p<0,05 foi considerado significativo para todas as análises.Resultados Ao todo, 60% dos pacientes atingiram o LV durante o teste de caminhada de 6 minutos. Mulheres (OR = 0,18 e IC95% = 0,05 a 0,64) e pacientes com mais aptidão cardiorrespiratória (OR = 0,56 e IC 95% = 0,40 a 0,77) tiveram menor probabilidade de chegar ao LV durante a caminhada em solo em comparação a homens e pacientes com menos aptidão cardiorrespiratória, respectivamente.Conclusão Mais da metade dos pacientes com DAP sintomática alcançou o LV durante o teste de caminhada de 6 minutos. Mulheres e pacientes com mais aptidão cardiorrespiratória têm menos probabilidade de chegar ao LV durante o teste de caminhada de 6 minutos, o que indica que a caminhada no solo pode ser mais intensa para esse grupo. Isso deve ser considerado ao se prescreverem exercícios de caminhada em solo para esses pacientes. (Arq Bras Cardiol. 2020; 114(3):486-492)

Individualized Relative-Intensity Physical Activity Accelerometer Cut Points.

Physical activity (PA) intensity is expressed as either absolute or relative intensity. Absolute intensity refers to the energy required to perform an activity. Relative intensity refers to a level of effort that takes into account how hard an individual is working relative to their maximum capacity. We sought to develop methods for obtaining individualized relative-intensity accelerometer cut points using data from a maximal graded exercise treadmill test (GXT) so that each individual has their own cut point. A total of 2363 men and women 38 to 50 yr old from the CARDIA fitness study wore ActiGraph 7164 accelerometers during a maximal GXT and for seven consecutive days in 2005-2006. Using mixed-effects regression models, we regressed accelerometer counts on heart rate as a percentage of maximum (%HRmax) and on RPE. Based on these two models, we obtained a moderate-intensity (%HRmax = 64% or RPE = 12) count cut point that is specific to each participant. We applied these subject-specific cut points to the available CARDIA accelerometer data. Using RPE, the mean moderate-intensity accelerometer cut point was 4004 (SD = 1120) counts per minute. On average, cut points were higher for men (4189 counts per minute) versus women (3865 counts per minute) and were higher for Whites (4088 counts per minute) versus African Americans (3896 counts per minute). Cut points were correlated with body mass index (rho = -0.11) and GXT duration (rho = 0.33). Mean daily minutes of absolute- and relative-intensity moderate to vigorous PA were 34.1 (SD = 31.1) min·d and 9.1 (SD = 18.2) min·d, respectively. RPE cut points were higher than those based on %HRmax. This is likely due to some participants ending the GXT before achieving their HRmax. Accelerometer-based relative-intensity PA may be a useful measure of intensity relative to maximal capacity.

Association Of Cardiovascular Health Trajectories And Cardiorespiratory Fitness: The Cardia Study

Ideal cardiovascular health (CVH) is a composite metric of seven health factors and behaviors. How cardiorespiratory fitness (CRF) is related to CVH is unclear. PURPOSE: To identify associations of CVH trajectories throughout adulthood with CRF in late-middle age. METHODS: CVH components were measured in Black and White adults (N=2723, aged 18-30 yrs. at baseline) in the CARDIA Study at seven in-person examinations over 20 years. Graded treadmill tests at years 0 and 20 were used to measure CRF (minutes duration). CVH was determined by assigning each metric a score of 2 (ideal), 1 (intermediate), or 0 (poor) and summing the scores (range 0-14). Latent class modeling was used to identify subgroups of individuals with similar CVH trajectories from young adulthood to middle age. Multivariable logistic Poisson regression was used to assess the association between 20-year CVH trajectories and race- and sex-specific quartiles of CRF at year 20. RESULTS: Five distinct CVH trajectories were identified: high (n=485), high-moderate (n=666), moderate (n=805), low-moderate (n=603), and low (n=164). Compared to the high trajectory group, odds ratios for low fitness (bottom quartile) at year 20 were 3.2 (95% CI: 1.9-5.2) for high-moderate, 6.6 (4.1-10.7) for moderate, 9.9 (6.1-16.4) for low-moderate, and 14.0 (8.2-24.0) for the low CVH trajectory groups after adjusting for race, sex, education, center, baseline CVH, and baseline CRF. CONCLUSION: Lower CVH trajectories throughout adulthood are associated with higher odds of low CRF in late-middle age.

Influence Of Vitamin D Status On The Post-exercise Hepcidin And Interleukin-6 Response In Trained Athletes

PURPOSE: Iron deficiency and reduced iron status have potential negative performance implications for athletes, particularly endurance runners. Hepcidin has a key role in iron homeostasis and is known to be influenced by interleukin (IL)-6. Emerging research from clinical populations indicates that vitamin D supplementation can reduce both circulating hepcidin and IL-6 levels hence could improve iron availability and increase performance. Exercise is known to increase both IL-6 and hepcidin levels, but the influence of vitamin D status on this response is unknown. METHODS: Twenty trained participants (24 ± 4 years; 184.3 ± 6.5 cm; 79.8 ± 7.5 kg; 55.7 ± 6.5 mL/min/kg) divided into 3 activity groups (endurance runners n=6; resistance trained n=6; team sports n=8) gave informed consent to take part in this study. Following an overnight fast, participants completed a sub-maximal and graded treadmill test to volitional exhaustion. Venous blood samples were collected pre, post, 1 h and 3 h post-exercise. Blood was analysed for serum total 25-hydroxy vitamin D at pre-exercise only; plasma hepcidin-25, plasma IL-6 and serum iron concentrations were assessed at all time points. RESULTS: Pre-exercise vitamin D values were similar between groups (90.2 ± 32.5 nM, p=0.563). Hepcidin increased significantly after exercise (F(1.1, 18.4)=36.81 p<0.001) with values peaking at 3 h post-exercise (pre 17.13 ± 12.15 ng/mL; 3 h post-exercise 38.44 ± 23.92 ng/mL). Both iron and IL-6 concentration increased significantly in response to exercise (F(1.9, 32.2)=44.1 p<0.001 and F(2.1, 36.4)=18.92 p<0.001, respectively). No significant interactions or group differences were found for hepcidin (p=0.121 and p=0.409), iron (p=0.529 and p=0.297) or IL-6 (p=0.709 and p=0.175). There was a significant negative correlation between peak hepcidin and relative VO2peak (rho=-0.468 p=0.038). There was a trend for a negative relationship between vitamin D values and % change in hepcidin from pre-exercise to 3 h post-exercise (r=-0.431 p=0.058) and a trend for a positive relationship between vitamin D and peak IL-6 values (r=0.410 p=0.072). CONCLUSIONS: Higher serum Vitamin D levels have the potential to reduce the post-exercise hepcidin response and therefore could have positive implications on athletes’ post-exercise iron status.