The purpose of this study was to determine the best scaling method to account for the effects of body size on measurements of overall cardiac function and subsequently the interpretation of data based on cardiac power output (CPO). CPO was measured at rest (CPO(rest)) and at maximal exercise (CPO(max)) on 88 and 103 healthy but untrained men and women, respectively, over the age range of 20-70 yr. Cardiac reserve (CR) was calculated as CPO(max) - CPO(rest). CPO(rest), CPO(max), and CR were all significantly related to body mass (BM), body surface area (BSA), and lean body mass (LBM). The linear regression model failed to completely normalize these measurements. In contrast, the allometric model produced size-independent values of CPO. Furthermore, all the assumptions associated with the allometric model were achieved. For CPO(rest), mean body size exponents were BM(0.33), BSA(0.60), and LBM(0.47). For CPO(max), the exponents were BM(0.41), BSA(0.81), and LBM(0.71). For CR, mean body size exponents were BM(0.44), BSA(0.87), and LBM(0.79). LBM was identified (from the root-mean-squares errors of the separate regression models) as the best physiological variable (based on its high metabolic activity) to be scaled in the allometric model. Scaling of CPO to LBM(b) (where b is the scaling exponent) dramatically reduced the between-gender differences with only a 7% difference in CPO(rest) and CPO(max) values. In addition, the gender difference in CR was completely removed. To avoid erroneous interpretations and conclusions being made when comparing data between men and women of different ages, the allometric scaling of CPO to LBM(b) would seem crucial.

Age-associated decline in muscle mass and strength impairs functional mobility in older adults. We examined the effects of an eccentric endurance exercise programme (downhill treadmill walking, DTW) at a self-selected walking speed (SSWS) on functional mobility and eccentric and concentric strength of m. quadriceps femoris of older adults. Twenty-four older adults (67 ± 4 years) were randomly assigned to complete 3 × 30 min treadmill walks per week for 12 weeks on a level (n = 11, LTW 0%) or downhill (n = 13, DTW -10%) treadmill gradient at SSWS. SSWS was re-adjusted every 4 weeks. Participants were assessed for five repetition sit-to-stand (5-RSTS), maximal walking speed (MWS), timed up-and-go (TUG) and dynamic strength. SSWS was similar for both groups with increases from 1.18 ± 0.11 to 1.53 ± 0.09 m s(-1) (LTW) and 1.26 ± 0.16 to 1.61 ± 0.12 m s(-1) (DTW) (time, P < 0.01). Improvements in 5-RSTS, MWS and TUG were substantial and similar for both groups (time, P < 0.01). 5-RSTS (baseline LTW: 8.50 ± 1.19 s, DTW: 8.54 ± 1.52 s) improved by 32 and 34%. MWS (baseline LTW: 2.39 ± 0.38 m s(-1), DTW: 2.40 ± 0.33 m s(-1)) improved by 22 and 23%. TUG (baseline LTW: 5.58 ± 0.51 s, DTW: 5.46 ± 0.89 s) improved by 22% for both groups. Peak eccentric and concentric torque did not change. Knee angle of concentric peak torque (180° s(-1)) was decreased after 12 weeks in both groups (LTW: 37° ± 16° to 26° ± 14°, DTW: 42° ± 18° to 37° ± 16°, P < 0.05). Regular level and downhill treadmill walking by older adults, at a SSWS, results in substantial improvements in functional mobility. Changes in functional mobility were not explained by changes in dynamic strength of the m. quadriceps femoris.

This study investigated the influence of age, sex, and aerobic capacity on resting and peak forearm and cutaneous blood flow (FBF, CBF). We recruited 93 female and 129 male subjects (age range 16-76 years). FBF and CBF were assessed by plethysmography and laser-Doppler flowmetry, respectively. Peak FBF was obtained following 5 min forearm vascular occlusion and peak CBF in response to local skin heating of 42 degrees C. Blood pressure was measured manually and by Finapres. Maximal oxygen uptake (VO2max) was obtained from a treadmill exercise stress test. Age was associated with declines in resting FBF (y = -1.176 ln(x) + 6.6899, r(2) = 0.45) and peak FBF (y = -17.21 ln(x) + 93.843, r(2) = 0.53) (both p < 0.05). Peak CBF decreased with increasing age (y = -223.6 ln(x) + 1,102.9, r(2) = 0.34) (p < 0.05), but resting CBF was unchanged (p > 0.05). Males had higher resting and peak FBF than females (p < 0.05) and these variables were related to ageing better in males (y = -1.245 ln(x) + 7.188, r(2) = 0.71 and y = -18.53 ln(x) + 102.82, r(2) = 0.69) than in females (y = -1.149 ln(x) + 6.4307, r(2) = 0.38 and y = -16.59 ln(x) + 88.872, r(2) = 0.55). There were no sex differences in resting CBF (p > 0.05). Peak CBF was much better related to ageing in males than females (y = -276.1 ln(x) + 1,365.4, r(2) = 0.53 vs. y = -183.1 ln(x) + 907.86, r(2) = 0.28). VO2max decreased with advancing age and this decline was associated with the decline in peak FBF (y = -0.5933x + 10.91, r(2) = 0.36, p < 0.05) but not with peak CBF (p > 0.05). These results suggest that healthy ageing is associated with a curvilinear decline in resting and peak forearm and peak cutaneous vasodilator capacity, with males more severely affected than females. The data indicate that peak FBF is influenced by VO2max but peak CBF is not.

Epicardial lead placement is a viable option for patients with unsuccessful coronary sinus lead placement. The improvements in most variables were of a similar magnitude and over a similar time scale compared with transvenous placement. Improvements in peak VO(2) were delayed in the epicardial group, probably as a result of a prolonged recovery time.

Cardiovascular responses of older adults to downhill (DTW, -10% incline) and level treadmill walking (0%) at self-selected walking speed (SSWS) were examined. Fifteen participants (age 68 ± 4 yr, height 1.69 ± 0.08 m, body mass 74.7 ± 8.1 kg) completed two 15-min walks at their SSWS (4.6 ± 0.6 km/hr). Cardiovascular responses were estimated using an arterial-volume finger clamp and infrared plethysmography. Oxygen consumption was 25% lower during DTW and associated with lower values for stroke volume (9.9 ml/beat), cardiac output (1.0 L/min), arteriovenous oxygen difference (a-vO, diff, 2.4 ml/L), and systolic blood pressure (10 mmHg), with no differences in heart rate or diastolic and mean arterial blood pressure. Total peripheral resistance (TPR) was higher (2.11 mmHg) during DTW. During downhill walking, an exercise performed with reduced cardiac strain, endothelial changes, and reduced metabolic demand may be responsible for the different responses in TPR and a-vOi diff. Future work is warranted on whether downhill walking is suitable for higher risk populations.