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Patrick B. Wilson

Background:

Psoriasis confers risk for cardiometabolic disorders. Cardiorespiratory fitness is inversely associated with risk of cardiometabolic disorders in other populations, but limited data have been published assessing cardiorespiratory fitness among individuals with psoriasis. This investigation aimed to: 1) assess cardiorespiratory fitness among individuals with psoriasis in the general population; and 2) compare levels to individuals without psoriasis.

Methods:

A secondary data analysis from the 2003–2004 National Health and Nutritional Examination Survey was performed. Cardiorespiratory fitness was assessed with a treadmill test, while measures of psoriasis severity included rating of psoriasis as a life problem and body surface area involvement.

Results:

Twenty-six of 1093 participants reported a psoriasis diagnosis (population weighted prevalence 2.9%). Individuals with psoriasis had lower cardiorespiratory fitness compared with individuals without psoriasis (36.2 vs. 39.1 mL∙kg-1∙min-1, P = .009). No differences in self-reported or accelerometer physical activity were found by psoriasis diagnosis. Cardiorespiratory fitness was not significantly lower in those reporting high life impairment or body surface area involvement.

Conclusions:

Cardiorespiratory fitness may be lower in individuals with psoriasis and these differences may not be explained by self-reported disease severity measures or physical activity. Future studies should examine whether validated measures of psoriasis severity predict lower cardiorespiratory fitness.

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Carmelo Bazzano, Lee N. Cunningham, Giovanni Cama and Tony Falconio

This study examined the physiology of the 1-mile walk test as administered in the field with 16 (7 M, 9 F) older adults (mean age 66.1 ± 5.9 yrs). Physiologic data were obtained via a Cosmed K2 miniaturized O2 analyzer with telemetric capabilities during a maximal treadmill (TM) test and a 1-mile walk test (MWT). Oxygen consumption (ml · kg−1 · min−1), minute ventilation (L · min−1), and heart rate (b · min−1) values obtained at maximal levels on the TM were 25.6 ± 7.6, 57 ± 17, and 155 ± 16, respectively. The measured V̇O2 submax during the MWT was 18.5 + 5, V̇E submax was 44 ± 10, and HR submax was 140 ± 19. The subjects were able to hold 74% of the V̇O2max, 81% of V̇Emax, and 91% of HR max. An upward drift for HR and V̇E was noted while V̇O2 remained constant throughout the MWT. The MWT with older subjects requires a vigorous level of metabolic and cardiorespiratory intensity. For healthy older adults who have been properly screened for hidden metabolic and cardiovascular diseases, participation in the MWT appears feasible.

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Candace D. Perkins, James M. Pivarnik and Matthew R. Green

Background:

The reliability and validity of the SensorMedics VmaxST was tested.

Methods:

Thirty subjects (age = 24.5 ± 4.0 years, height = 174.8 ± 9.8 cm, weight = 70.3 ± 12.6 kg) performed treadmill exercise on three occasions, twice using the VmaxST and once using the SensorMedics 2900 system. Oxygen consumption (VO2; L/min) and heart rate (HR; beats/min) were measured continuously during three, 6- minute stages: 80 m/min, 0% grade; 94 m/min, 5% grade; and 160 m/min, 0% grade, and VO2max.

Results:

Reliability was high, and measurement error was low for VO2 (Rxx range = 0.97 - 0.99, CI = 0.94 - 1.00, SEM = 0.03 - 0.08 L/min) and HR (Rxx = 0.94 - 0.99, CI = 0.88 - 1.00, SEM = 1.8 - 3.2 beats/min). Validity was high for VO2 (Rxy range = 0.92 - 0.98, CI = 0.84 - 0.99, SEE = 0.08 - 0.21 L/min) and HR (Rxy = 0.97 - 0.99, CI = 0.94 - 1.00, SEE = 0.9 - 1.8 beats/min). Mean differences in VO2 between VmaxST and 2900 were small yet significant (P < 0.001).

Conclusions:

The VmaxST demonstrated excellent reliability and validity for measuring VO2 and HR over several exercise intensities. Small overestimates in VO2 by the VmaxST are countered by low measurement error.

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Michael R.M. McGuigan, Roger Bronks, Robert U. Newton, John C. Graham and David V. Cody

Peripheral arterial disease (PAD) is associated with impaired lower extremity function. This study investigated differences in PAD and control participants and the relationship between lower limb strength and clinical measures of PAD severity. Participants were evaluated by 6-min-walk distance, normal and maximal walking speed over 10 m, isometric plantar-flexion strength, and dynamic dorsi-/plantar-flexion strength. Hemodynamic measures of the lower limbs were recorded at rest and after maximal treadmill testing. PAD participants walked significantly less far during the 6-min walk, and there were large differences in normal and maximal walking speeds. Small to moderate differences were found for isometric plantar-flexion strength. In the diseased legs of the PAD participants, resting systolic hallux photoplethysmography was significantly correlated with isokinetic plantar-flexion strength and onset of claudication pain during the 6-min-walk test. In addition to confirming the documented loss of walking endurance, these data suggest that loss of strength of the plantar flexors is associated with increasing PAD impairment.

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Andréa L. Maslow, Anna E. Price, Xuemei Sui, Duck-chul Lee, Ikka Vuori and Steven N. Blair

Background:

This study examined the associations of body mass index (BMI), waist circumference (WC), and cardiorespiratory fitness (CRF) with incident functional limitation (IFL) in adults.

Methods:

Patients (n = 2400), 30+ years [mean age, 45.2 (SD, 8.3); 12% women], completed a baseline health examination during 1979 to 1995. CRF was quantified by age-and sex-specific thirds for maximal treadmill exercise test duration. Adiposity was assessed by BMI and WC (grouped for analysis according to clinical guidelines). Incident IFL was identified from mail-back surveys during 1995, 1999, and 2004.

Results:

After adjusting for potential confounders and either BMI or WC, CRF was inversely related to IFL (P trend < .001). The association between BMI and IFL was significant after adjusting for all confounders (P trend = .002), but not after additional adjustment for CRF (P trend = .23). After controlling for all confounders and CRF, high WC was associated with greater odds of IFL in those aged 30 to 49; normal WC was associated with greater odds of IFL in those aged 50+.

Conclusions:

CRF was a significant predictor of IFL in middle aged and older adults, independent of overall or abdominal adiposity. Clinicians should consider the importance of preserving functional capacity by recommending regular physical activity for normal-weight and overweight individuals.

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Sae Young Jae, Kevin Heffernan, Bo Fernhall and Yoon-Ho Choi

Background:

We tested the hypothesis that higher levels of cardiorespiratory fitness are inversely associated with carotid artery intima media thickness in 746 (age 53 ± 7 yrs) men with type 2 diabetes.

Methods:

We measured common carotid intima media thickness and defined carotid atherosclerosis as a carotid intima media thickness > 1.0 mm. Cardiorespiratory fitness was directly measured by peak oxygen uptake using expired gases analysis during a standard treadmill test.

Results:

Cardiorespiratory fitness was independently associated with common carotid intima media thickness in multivariable regression (β = –0.15, P < .05). After adjusting for established risk factors, high and moderate cardiorespiratory fitness were associated with lower odds ratios for having carotid atherosclerosis—0.49 (95% CI, 0.30–0.81), and 0.59 (95% CI, 0.38–0.92), respectively—as compared with low cardiorespiratory fitness. Each 1 metabolic equivalent increment higher cardiorespiratory fitness was associated with 27% (OR = 0.73; 95% CI, 0.61–0.87) lower prevalence of carotid atherosclerosis.

Conclusions:

These results suggest that high cardiorespiratory fitness is inversely associated with common carotid intima media thickness in men with type 2 diabetes.

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Gianluca Vernillo, Aldo Savoldelli, Barbara Pellegrini and Federico Schena

Background:

Accurate assessments of physical activity and energy expenditure (EE) are needed to advance research on positive and negative graded walking.

Purpose:

To evaluate the validity of 2 SenseWear Armband monitors (Pro3 and the recently released Mini) during graded walking.

Methods:

Twenty healthy adults wore both monitors during randomized walking activities on a motorized treadmill at 7 grades (0%, ±5%, ±15%, and ±25%). Estimates of total EE from the monitors were computed using different algorithms and compared with values derived from indirect calorimetry methodology using a 2-way mixed model ANOVA (Device × Condition), correlation analyses and Bland-Altman plots.

Results:

There was no significant difference in EE between the 2 armbands in any of the conditions examined. Significant main effects for device and condition, as well as a consistent bias, were observed during positive and negative graded walking with a greater over- and under-estimation at higher slope.

Conclusions:

Both the armbands produced similar EE values and seem to be not accurate in estimation of EE during activities involving uphill and downhill walking. Additional work is needed to understand factors contributing to this discrepancy and to improve the ability of these monitors to accurately measure EE during graded walking.

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Fiona Iredale, Frank Bell and Myra Nimmo

Fourteen sedentary 50- to 55-year-old men were exercised to exhaustion using an incremental treadmill protocol. Mean (±SEM) peak oxygen uptake (V̇O2peak) was 40.5 ± 1.19 ml · kg1 · min−1, and maximum heart rate was 161 ± 4 beats · min−1. Blood lactate concentration was measured regularly to identify the lactate threshold (oxygen consumption at which blood lactate concentration begins to systematically increase). Threshold occurred at 84 ± 2% of V̇O2peak. The absolute lactate value at threshold was 2.9 ± 0.2 mmol · L−1. On a separate occasion, 6 subjects exercised continuously just below their individual lactate thresholds for 25 min without significantly raising their blood lactate levels from the 10th minute to the 25th. The absolute blood lactate level over the last 20 min of the steady-state test averaged 3.7 ± 1.2 mmol · L−1. This value is higher than that elicited at the threshold in the incremental test because of the differing nature of the protocols. It was concluded that although the lactate threshold occurs at a high percentage of V̇O2peak, subjects are still able to sustain exercise at that intensity for 25 min.

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Charles F. Morgan, Allison R. Tsuchida, Michael William Beets, Ronald K. Hetzler and Christopher D. Stickley

Background:

Physical activity guidelines for youth and adults include recommendations for moderate intensity activity to attain health benefits. Indirect calorimetry studies have consistently reported a 100 ste·min−1 threshold for moderate intensity walking in adults. No indirect calorimetry studies have investigated step-rate thresholds in children and therefore the primary purpose of the study was to determine preliminary step-rate thresholds for moderate physical activity walking in children.

Methods:

Oxygen consumption was measured at rest and used to determine 3 and 4 age-adjusted metabolic equivalents (A-AMETs) for 4 treadmill trials (self-selected, 2.5, 3.0, and 3.5 MPH). Two trained observers simultaneously counted children’s steps during each walking trial. Step-rate thresholds associated with moderate-intensity activity, defined as 3 and 4 A-AMETs, were determined using hierarchical linear modeling.

Results:

Regression analysis determined an overall step rate of 112 and 134 step·min-1 for 3 and 4 A-AMETs respectively. Body mass index (BMI) weight status and age were positively related to A-AMETs.

Conclusions:

We suggest age and BMI weight status specific recommendations that range from a low of 100 step·min-1 threshold (3 A-AMETs) for overweight/obese 11- to 12-year-olds to a high of 140 step·min-1 threshold (4 A-AMETs) for healthy weight 9- to 10-year-old children.

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David A. Rowe, David McMinn, Leslie Peacock, Arjan W. P. Buis, Rona Sutherland, Emma Henderson and Allan Hewitt

Background:

Walking cadence has shown promise for estimating walking intensity in healthy adults. Auditory cues have been shown to improve gait symmetry in populations with movement disorders. We investigated the walking cadence-energy expenditure relationship in unilateral transtibial amputees (TTAs), and the potential of music cues for regulating walking cadence and improving gait symmetry.

Methods:

Seventeen unilateral TTAs performed 2 5-min treadmill walking trials, followed by 2 5-min overground walking trials (self-regulated “brisk” intensity, and while attempting to match a moderate-tempo digital music cue).

Results:

Walking cadence significantly (P < .001) and accurately (R 2 = .55, SEE = 0.50 METs) predicted energy expenditure, and a cadence of 86 steps·min−1 was equivalent to a 3-MET intensity. Although most participants were able to match cadence to prescribed music tempo, gait symmetry was not improved during the music-guided condition, compared with the self-regulated condition.

Conclusions:

This is the first study to investigate the utility of walking cadence for monitoring and regulating walking intensity in adults with lower limb prosthesis. Cadence has similar or superior accuracy as an indicator of walking intensity in this population, compared with the general population, and adults with a unilateral TTA are capable of walking at moderate intensity and above for meaningful bouts of time.