Aerobic fitness levels and validation of a non exercise VO2max prediction equation for HIV-infected patients on HAART.

BACKGROUND: Non-exercise (N-EX) questionnaires have been developed to determine maximal oxygen consumption (VO2max) in healthy populations. There are limited reliable and validated N-EX questionnaires for the HIV+ population that provide estimates of habitual physical activity and not VO2max. OBJECTIVES: To determine how well regression equations developed previously on healthy populations, including N-EX prediction equations for VO2max and age-predicted maximal heart rates (APMHR), worked on an HIV+ population; and to develop a specific N-EX prediction equation for VO2max and APMHR for HIV+ individuals. METHODS: Sixty-six HIV+ participants on stable HAART completed 4 N-EX questionnaires and performed a maximal graded exercise test. RESULTS: Sixty males and 6 females were included; mean (SD) age was 49.2 (8.2) years; CD4 count was 516.0 ± 253.0 cells·mm-3; and 92% had undetectable HIV PCR. Mean VO2max was 29.2 ± 7.6 (range, 14.4-49.4) mL·kg-1·min-1 Despite positive correlations with VO2max, previously published N-EX VO2max equations produced results significantly different than actual VO2 scores (P < .0001). An HIV+ specific N-EX equation was developed and produced similar mean VO2max values, R = 0.71, when compared to achieved VO2max (P = .53). CONCLUSION: HIV+ individuals tend to be sedentary and unfit, putting them at increased risk for the development of chronic diseases associated with a sedentary lifestyle. Based on the level of error associated with utilizing APMHR and N-EX VO2max equations with HIV+ individuals, neither should be used in this population for exercise prescription.

Middle and Elementary School Students' Changes in Self-Determined Motivation in a Basketball Unit Taught using the Tactical Games Model.

Studies examining student motivation levels suggest that this is a significant factor in students' engagement in physical education and may be positively affected when teachers employ alternative pedagogical models such as game-centered approaches (GCAs). The aim of this study was to investigate changes in self-determined motivation of students as they participated in a GCA-basketball unit taught using the Tactical Games Model (TGM). Participants were 173 students (84 girls), 79 middle school (45 girls) and 94 (39 girls) elementary school students from four seventh and five fourth/fifth grade co-educational classes. Two teachers taught 32 (middle) and 33 (elementary) level one TGM basketball lessons. Need satisfaction and self-determined motivation data were collected using a previously validated instrument, while lesson context and teacher behavior data were recorded using systematic observation instruments. Repeated measures MANOVAs were employed to examine pre-posttest differences. Results revealed a significant main effect for time in need satisfaction for both middle (relatedness increased) and elementary school students (autonomy decreased) and a significant main effect in self-determined motivation for middle school students only (introjected regulation, external regulation, and amotivation all increased). Approximately 48%/42% (middle/elementary) of lesson time was game play, 22%/22% skill practice, 17%/17% management, and 13%/19% knowledge. The primary teacher behaviors used were instruction, management, specific observation, corrective feedback and modelling. Results indicate that it is important for future research to pay greater attention to the contextual factors associated with the application of the TGM, such as the students' previous exposure to TGM lessons, and the teachers' training and experience in utilizing the TGM. Indeed, results of the present study demonstrate that a longer-term commitment to the TGM is necessary to reduce controlling teacher behaviors, which will lead to positive changes in students' need satisfaction and self-determined motivation. Future research is therefore needed to embrace this challenge to provide an increased evidence-base for GCAs such as the TGM.

Short Communication: HIV Patient Systemic Mitochondrial Respiration Improves with Exercise.

In HIV-infected individuals, impaired mitochondrial function may contribute to cardiometabolic disease as well as to fatigue and frailty. Aerobic exercise improves total body energy reserves; however, its impact at the cellular level is unknown. We assessed alterations in cellular bioenergetics in peripheral blood mononuclear cells (PBMC) before and after a 12-week aerobic exercise study in sedentary HIV-infected subjects on stable antiretroviral therapy who successfully completed a 12-week aerobic exercise program. In this prospective study, participants underwent supervised 20-40 min of light aerobic exercise (walking or jogging) performed three times per week for 12 weeks, gradually increasing to maintain an intensity of 50%-80% of heart rate reserve. Maximal aerobic capacity (VO2MAX) was assessed by a graded exercise test on a cycle ergometer before and after completion of the study. PBMC from compliant subjects (attended at least 70% of exercise sessions) were assessed for mitochondrial respiration using the Seahorse XF24 Bio-Analyzer. Seven of 24 enrolled subjects were compliant with the exercise regimen. In these individuals, a significant increase (p = .04) in VO2MAX over 12 weeks was found with a median increase of 14%. During the same interval, a 2.45-fold increase in PBMC mitochondrial respiratory capacity (p = .04), a 5.65-fold increase in spare respiratory capacity (p = .01), and a 3.15-fold (p = .04) increase in nonmitochondrial respiration was observed. Aerobic exercise improves respiration at the cellular level. The diagnostic and prognostic value of such improved cellular respiration in the setting of chronic HIV warrants further investigation.

Autonomic Function is Associated with Fitness Level in HIV-Infected Individuals.

BACKGROUND: Cardiovascular fitness can improve autonomic function (AF) in human immunodeficiency virus (HIV)-infected individuals. METHODS: Cross-sectional study investigating relationship between AF and cardiovascular fitness in HIV+ individuals on antiretroviral therapy. Participants' (n=29) maximal oxygen consumption (VO2MAX) were assessed by graded exercise test and scaled allometrically, then divided into tertiles by fitness level (Unfit, Low-fit, and Moderately-fit). Heart rate variability (HRV) and the Autonomic Reflex Screen were used to assess AF. RESULTS: Median VO2MAX were 104.9, 130.5, and 150.2 mL•kg-.67•min-1 for Unfit (n=10), Low-fit (n=10), and Moderately-fit (n= 9) groups respectively (p<0.05). Positive correlations were found between VO2MAX and HRV (Spearman's rho range 0.383 to 0.553) were found. Quantitative Sudomotor Axon Reflex Test (QSART) Distal Leg volumes was lower in Unfit compared to Low-fit (p=0.007) and Moderately-fit groups (p=0.018). Unfit QSART total volumes was lower than Moderately-fit (p=0.014). CONCLUSION: A positive relationship existed between AF and fitness levels. HIV+ individuals could benefit from improved fitness.