Jeremy A. Patterson

Moderate-intensity resistance exercise training in patients with chronic heart failure improves strength, endurance, heart rate variability, and forearm blood flow

BACKGROUND Resistance exercise training was applied to patients with chronic heart failure (CHF) on the basis that it may partly reverse deficiencies in skeletal muscle strength and endurance, aerobic power (VO(2peak)), heart rate variability (HRV), and forearm blood flow (FBF) that are all putative factors in the syndrome. METHODS AND RESULTS Thirty-nine CHF patients (New York Heart Association Functional Class=2.3+/-0.5; left ventricular ejection fraction 28%+/-7%; age 65+/-11 years; 33:6 male:female) underwent 2 identical series of tests, 1 week apart, for strength and endurance of the knee and elbow extensors and flexors, VO(2peak), HRV, FBF at rest, and FBF activated by forearm exercise or limb ischemia. Patients were then randomized to 3 months of resistance training (EX, n=19), consisting of mainly isokinetic (hydraulic) ergometry, interspersed with rest intervals, or continuance with usual care (CON, n=20), after which they underwent repeat endpoint testing. Combining all 4 movement patterns, strength increased for EX by 21+/-30% (mean+/-SD, P<.01) after training, whereas endurance improved 21+/-21% (P<.01). Corresponding data for CON remained almost unchanged (strength P<.005, endurance P<.003 EX versus CON). VO(2peak) improved in EX by 11+/-15% (P<.01), whereas it decreased by 10+/-18% (P<.05) in CON (P<.001 EX versus CON). The ratio of low-frequency to high-frequency spectral power fell after resistance training in EX by 44+/-53% (P<.01), but was unchanged in CON (P<.05 EX versus CON). FBF increased at rest by 20+/-32% (P<.01), and when stimulated by submaximal exercise (24+/-32%, P<.01) or limb ischemia (26+/-45%, P<.01) in EX, but not in CON (P<.01 EX versus CON). CONCLUSIONS Moderate-intensity resistance exercise training in CHF patients produced favorable changes to skeletal muscle strength and endurance, VO(2peak), FBF, and HRV.

Reliability of isokinetic strength and aerobic power testing for patients with chronic heart failure

PURPOSE The objective of this study was to assess the reliability of testing skeletal muscle strength and peak aerobic power in a clinical population of patients with chronic heart failure (CHF). METHODS Thirty-three patients with CHF (New York Heart Association (NYHA) Functional Class 2.3 +/- 0.5; left ventricular ejection fraction 27% +/- 7%; age 65 +/- 9 years; 28:5 male-female ratio) underwent two identical series of tests (T1 and T2), 1 week apart, for strength and endurance of the muscle groups responsible for knee extension/flexion and elbow extension/flexion. The patients also underwent two graded exercise tests on a bicycle ergometer to measure peak oxygen consumption (VO(2peak)). Three months later, 18 of the patients underwent a third test (T3) for each of the measures. Means were compared using MANOVA with repeated measures for strength and endurance, and ANOVA with repeated measures for VO(2peak). RESULTS Combining data for all four movement patterns, the expression of strength increased from T1 to T2 by 12% +/- 25% (P <.001; intraclass correlation coefficient [ICC] = 0.89). Correspondingly, endurance increased by 13% +/- 23% (P =.004; ICC = 0.87). Peak oxygen consumption was not significantly different (16.2 +/- 0.8 and 16.1 +/- 0.8 mL.kg(-1).min(-1) for T1 and T2, respectively; P =.686; ICC = 0.91). There were no significant differences between T2 and T3 for strength (2% +/- 17%; P =.736; ICC = 0.92) or muscle endurance (-1% +/- 15%; P =.812; ICC = 0.96), but VO(2peak) decreased from 16.7 +/- 1.2 to 14.9 +/- 0.9 mL.kg(-1).min(-1) (-10% +/- 18%; P =.021; ICC = 0.89). CONCLUSIONS These data suggest that in a population of patients with CHF, a familiarization trial for skeletal muscle strength testing is necessary. Although familiarization is not required for assessing oxygen consumption as a single measurement, VO(2peak) declined markedly in the 3-month period for which these patients were followed. Internal consistency within patients was high for the second and third strength trials and the first and second tests of VO(2peak).

Exercise capacity in an individual with LVAD explantation without heart transplantation.

PURPOSE: Left ventricular assist devices (LVADs) have become a viable treatment alternative to heart transplantation, in some instances providing for a level of improvement of native heart function to allow for device explantation. The aim of this case study was to describe changes in physical work capacity following 9 months of LVAD support. CLINICAL CASE: The patient described here was diagnosed with idiopathic dilated cardiomyopathy and demonstrated worsening heart failure over a 5-year period with a maximum left ventricular end-diastolic diameter of 8.99 cm and an ejection fraction of 15% to 25%. Upon implantation of an LVAD, central hemodynamic function improved and the device was removed after 9 months of support. Left ventricular diastolic and systolic diameter decreased by 39.8% and more than 30%, respectively. The left atrium decreased by 21.7% and ejection fraction was maintained by the LVAD and stabilized at 20%. Four months postexplantation, a cycle ergometry graded cardiopulmonary exercise test was performed. Exercise began at 0 W and increased 25 W per 3-minute stage. RESULTS: The patient showed improvement in peak aerobic capacity when compared to pre-LVAD cardiopulmonary stress tests. Peak oxygen uptake increased from pre-LVAD measures of 11.8 mL · kg−1 · min−1 to 17.0 mL · kg−1 · min−1. Time to maximal exertion increased from 5 minutes 27 seconds to 15 minutes. CONCLUSION: Results of this case study indicate that significant improvements in native heart function leading to an increased ability to perform work is possible following a period of mechanical unloading through LVAD support.

Comparison of Postural Sway Measures Using a Balance Platform and Mobile Application: 3378 Board #22 May 31, 8

Methods Results Conclusions Introduction Balance training has become common in therapeutic exercise routines for rehab, injury prevention, and fall prevention. Unstable surfaces such as foam pads are commonly used in these to improve balance. While postural sway is often used as a measure of balance ability and to evaluate the efficacy of such programs to improve postural balance, there is little research regarding the measurement of sway while standing on foam pads. Evaluating clinical balance has typically been performed using expensive force platform technology that presents issues of portability, cost and ease of use. The use of smartphones equipped with accelerometers to measure balance is a novel technique for measuring postural sway. The purpose of this study was to compare measures of postural sway on firm and foam surfaces from a clinical balance platform against a mobile application. Participants ▪57 participants (28 male; 29 female) ▪Ages 24.3 + 6.8 yr Protocol ▪ 2 devices were used to obtain postural dynamics of static balance: ▪ a balance platform (Biodex Balance System SD) ▪ a mobile application (SWAY Balance) that utilizes the built-in triaxial accelerometer within an iPod Touch to measure balance. ▪The mobile device was held against the chest so data collection on both devices was performed simultaneously. ▪Each device measured anterior/posterior and medial/lateral stability as the displacement in degrees from level. (Actual Stability Score.) ▪Stances: stable surface feet together with eyes closed, feet together eyes closed on a foam surface, single leg eyes closed on stable surface. and single leg eyes closed on foam surface. There were no significant differences between the two devices as measured on the firm surface. There was a difference (p<0.05) when standing on foam (balance platform = 3.775; mobile application = 5.659) between the two devices. Unilateral stance on foam (9.887) was higher (p<0.05) than unilateral stance on the solid surface (4.862) with only the mobile application. Balance training has become common in therapeutic exercise routines for rehabilitation, injury prevention, and fall prevention. Unstable surfaces such as foam pads are commonly used in these purportedly to improve balance. While postural sway is often used as a measure of balance ability and to evaluate the efficacy of such programs to improve postural balance, there is little research regarding the measurement of sway while standing on foam pads. Purpose: To compare measures of postural sway from a clinical balance platform against a mobile application. Method: Two devices were used to obtain the postural dynamics of static balance for each subject: 1) a balance platform (Biodex Balance System SD) and 2) a mobile application (SWAY Balance) that utilizes the built-in tri-axial accelerometer within an iPhone or iPod Touch to measure balance. The mobile device is held against the chest so data from both devices can be collected simultaneously. 57 participants (28 male; 29 female) aged 24.3 + 6.8 yr completed the study in which they stood bilaterally and then unilaterally on a firm surface and then on foam pads using both devices to evaluate postural sway. Results: There were no significant differences between the two devices as measured on the firm surface. However, there was a difference (p<0.05) when standing on foam (balance platform = 3.775; mobile application = 5.659) between the two devices. Unilateral stance on foam (9.887) was higher (p<0.05) than unilateral stance on the solid surface (4.862) with only the mobile application. Conclusion: Based on these results, the mobile application is a valid and useful clinical tool for the evaluation of balance as results did not differ with the balance platform when measuring balance on the stable surface. However, given that postural sway did not differ between unilateral stance on firm versus foam surfaces with the balance platform, it appears that the balance platform strain gauges do not effectively measure sway while standing on foam. Therefore, this mobile application may be a better tool for quantification of sway while standing on foam. The mobile application is a valid and useful clinical tool for the evaluation of balance as results did not differ with the balance platform when measuring balance on the stable surface. Given that postural sway did not differ between unilateral stance on firm versus foam surfaces with the balance platform, it appears that the balance platform does not effectively measure sway while standing on foam. Therefore, this mobile application may be a better tool for quantification of sway while standing on foam.