High levels of cardiovascular fitness and physical activity are associated with higher levels of cognitive function in people with HIV, thus, they may reduce the risk of developing HIV-associated neurocognitive disorder (HAND). This study aimed to investigate the effects of a 16-week aerobic exercise intervention on cognitive function in people with HIV. Eleven participants living with HIV were recruited into the study. Participants were randomised into either an exercise group (n = 5), that completed a 16-week aerobic exercise programme training, 3 times per week (2 supervised sessions and one unsupervised session) or a control group (n = 6) that received no intervention. Outcomes measured included cognitive function (Montreal cognitive assessment (MOCA) and the Trail making tests A and B), aerobic fitness (modified Bruce protocol), sleep quality (Pittsburgh sleep quality index; PSQI) and physical activity levels (seven-day accelerometry). At baseline, higher levels of moderate physical activity were positively correlated with higher MOCA scores and levels of aerobic fitness were negatively associated with Trail A scores (P = 0.04 and P = 0.001 respectively). However, exercise training did not induce any significant improvements in cognitive function or aerobic fitness. The overall mean adherence rate to the exercise programme was 60%. In conclusion, in the present study a 16-week aerobic exercise intervention did not affect the cognitive function of participants with HIV. It is likely that longer intervention periods and/or higher adherence rates to exercise might be needed for an aerobic exercise programme to be effective in improving cognitive function in a cohort with no baseline cognitive impairments.

O'Connor E, Kiely C, O'Shea D, Green S, Egaña M. Similar level of impairment in exercise performance and oxygen uptake kinetics in middle-aged men and women with type 2 diabetes. Am J Physiol Regul Integr Comp Physiol 303: R70 -R76, 2012. First published April 25, 2012 doi:10.1152/ajpregu.00012.2012.-The present study tested the hypothesis that the magnitude of the type 2 diabetes-induced impairments in peak oxygen uptake (V O2) and V O2 kinetics would be greater in females than males in middle-aged participants. Thirty-two individuals with type 2 diabetes (16 male, 16 female), and 32 age-and body mass index (BMI)-matched healthy individuals (16 male, 16 female) were recruited. Initially, the ventilatory threshold (VT) and peak V O2 were determined. On a separate day, subjects completed four 6-min bouts of constant-load cycling at 80% VT for the determination of V O2 kinetics using standard procedures. Cardiac output (CO) (inert gas rebreathing) was recorded at rest, 30, and 240 s during two additional bouts. Peak V O2 (ml·kg ). The time constant (s) of phase 2 (2) and mean response time (s) of the V O2 response (MRT) were slowed in women with type 2 diabetes compared with healthy women (2, 43.3 Ϯ 9.8 vs. 33.6 Ϯ 10.0 s; MRT, 51.7 Ϯ 9.4 vs. 43.5 Ϯ 11.4s) and in men with type 2 diabetes compared with nondiabetic men (2, 43.8 Ϯ 12.0 vs. 35.3 Ϯ 9.5 s; MRT, 57.6 Ϯ 8.3 vs. 47.3 Ϯ 9.3 s). The magnitude of these impairments was not different between males and females. The steady-state CO responses or the dynamic responses of CO were not affected by type 2 diabetes among men or women. The results suggest that the type 2 diabetes-induced impairments in peak V O2 and V O2 kinetics are not affected by sex in middle aged participants. cycling; sex; cardiac output MAXIMAL AEROBIC CAPACITY, expressed as maximum oxygen uptake (V O 2 ), which is an independent risk factor for all-cause and cardiovascular disease mortality (27) has been consistently reported to be reduced in individuals with type 2 diabetes compared with nondiabetic counterparts of similar age, weight, and activity levels (8,17,32). Additionally, the rate of adjustment of oxygen uptake (V O 2 kinetics) to steady-state exercise is slower in young and middle-aged women (8, 21, 32) and in a combined group of middle-aged men and women (4), although recent data suggests that V O 2 kinetics are not impaired in older men with type 2 diabetes compared with age-matched healthy controls (42). The slowing of the V O 2 kinetic response is associated with a faster onset of fatigue and lower exercise tolerance (28) and might help explain why individuals with type 2 diabetes perceive light/moderate exercise as more difficult than healthy controls (12). Ultimately this often leads to a sedentary behavior or physical inactivity, which is associated with worsening of cardiovascular outcomes and predicts mortality in people with type 2 diabetes (6, 39). The mechanisms underpinning these exercise impairments in younger and middle-aged individuals with type 2 diabetes have not been...

To explore the effect of posture on muscle performance, we tested the effects of body tilt angle on the strength, endurance, and fatigue of, and blood flow into, the plantar flexors. Human subjects were fixed to a tilt table that could tilt them from the horizontal (0 degrees ) to upright (90 degrees ) position and enabled force to be applied to a footplate through isometric action of the right calf muscle. In experiment 1, six subjects performed a strength test and graded test (intermittent contractions) to the point of failure at three tilt angles (0, 47, and 90 degrees ). In Experiment 2, seven subjects performed a strength test and constant-force test [70% maximum force (F(max)); intermittent contractions] to the point of failure in the horizontal and three inclined positions (32, 47, and 67 degrees ). In experiment 3, leg blood flow was assessed during constant-force exercise at two intensities (30 and 70% F(max)) and two tilt angles (0 and 67 degrees ) in six subjects. Strength was not affected (P > 0.05) by tilt angle. Time to failure during the graded test was significantly higher at 47 degrees (25.9 +/- 2.0 min) and 90 degrees (25.1 +/- 3.0 min) than 0 degrees (22.2 +/- 2.6 min). Time to failure during the constant-force test was also significantly higher at 32 degrees (7.1 +/- 3.6 min), 47 degrees (8.0 +/- 5.2 min), and 67 degrees (8.6 +/- 5.6 min) compared with 0 degrees (4.0 +/- 2.6 min). When graded or constant-force exercise was performed with arterial flow to the leg eliminated, there were no differences in exercise time between the horizontal and an inclined position. During nonischemic exercise, leg blood flow was significantly higher during exercise in the inclined position. These results demonstrate that head-up tilt improves endurance of the plantar flexors, that this effect occurs in the absence of an effect on strength, and that it depends on an intact peripheral circulation. Moreover, the postural effect on muscle endurance appears to be due to a greater blood flow into the leg, an effect that is established during the initial contractions.

We investigated if the magnitude of the type 2 diabetes (T2D)-induced impairments in peak oxygen uptake (V̇o2) and V̇o2 kinetics was affected by age. Thirty-three men with T2D (15 middle-aged, 18 older), and 21 nondiabetic (ND) men (11 middle-aged, 10 older) matched by age were recruited. Participants completed four 6-min bouts of constant-load cycling at 80% ventilatory threshold for the determination of V̇o2 kinetics. Cardiac output (inert-gas rebreathing) was recorded at rest and 30 and 240 s during two additional bouts. Peak V̇o2 (determined from a separate graded test) was significantly (P < 0.05) reduced in middle-aged and older men with T2D compared with their respective ND counterparts (middle-aged, 3.2 ± 0.5 vs. 2.5 ± 0.5 l/min; older, 2.7 ± 0.4 vs. 2.4 ± 0.4 l/min), and the magnitude of these impairments was not affected by age. However, the time constant of phase II of the V̇o2 response was only slowed (P < 0.05) in middle-aged men with T2D compared with healthy counterparts, whereas it was similar among older men with and without T2D (middle-aged, 26.8 ± 9.3 vs. 41.6 ± 12.1 s; older, 40.5 ± 7.8 vs. 41.1 ± 8.5 s). Similarly, the "gains" in systemic vascular conductance (estimated from the slope between cardiac output and mean arterial pressure responses) were lower (P < 0.05) in middle-aged men with T2D than ND controls, but similar between the older groups. The results suggest that the mechanisms by which T2D induces significant reductions in peak exercise performance are linked to a slower dynamic response of V̇o2 and reduced systemic vascular conductance responses in middle-aged men, whereas this is not the case in older men.

The results confirm that type 2 diabetes slows the dynamic response of VO2 during light and moderate relative intensity exercise in females but that this occurs in the absence of any slowing of the CO response during the initial period of exercise.