Research Highlights

MANUSCRIPT REVIEW

The purpose of this investigation was to compare BP change associated with chronic evening versus morning aerobic training and assess if evening training could be used as a method to enhance BP reductions. Based on previous research with acute exercise, the authors of this study hypothesized that 10 weeks of evening aerobic training would have superior chronic reductions in BP when compared to morning training. Men (age 30–65 years) living in the São Paulo area of Brazil were recruited to participate. Inclusion criteria included age, resting systolic and diastolic BP < 160 mm Hg and < 105 mm Hg, respectively, and treated with an antihypertension medication without change in dosage for the previous 4 months. Patients underwent a physical exam to determine resting BP (average of 6 measures on 2 separate days), measure height, weight, body mass index, perform a resting electrocardiograph (ECG), collect blood and urine samples to rule out organ damage and secondary hypertension, and determined chronotype, related to circadian rhythm based on sleep patterns, by completing the Horne and Ostberg questionnaire (9).

The study was a randomized, controlled trial that used the primary outcome of resting BP and the secondary outcome of autonomic function. Patients were randomized to 1 of 3 groups (evening training [ET] 6–8pm; morning training [MT] 7–9am; controls [CT]). The times selected were to control for circadian effects of BP increases and decreases during the evenings and mornings. Patients engaged in 10 weeks of training that included three 30 to 45-min sessions of progressive lower body cycling. During cycling the intensity was set to the heart rate associated with each participant's anaerobic threshold determined during the initial graded exercise testing (GXT) and progressively increased every 2 weeks until the heart rate of 10% below respiratory compensation threshold was achieved. Duration gradually increased from 30 to 45 min over the first 4 weeks of training. Control patients performed three 30-min sessions of static stretching.

Pre-post testing was completed within 3 to 4 d prior to and after the 10-week intervention, and included 2 GXTs during the evening and morning time periods with 2 d between each test. During GXT, BP was taken every 2 min and heart rate, ECG, and expired gas were continually measured. For resting BP all patients reported to the laboratory with at least 4 h of fasting. Patients were fed a standardized meal 30 min prior to the first resting BP measure. All resting BP measures were conducted with patients during both the morning and evening sessions with at least 2 d between each measure. Cardiac output was calculated via the indirect Fick method of CO₂ rebreathing, and SVR was calculated as mean BP/cardiac output. Autonomic modulation of the cardiovascular system was measured using heart rate (measured with R-R interval on ECG) and beat-by-beat BP (measured with photoplethysmography and thoracic piezoelectric belt) variability.

A total of 210 individuals were screened for this study; 88 men agreed to participate (32 patients dropped after the initial evaluation), and 56 patients were randomized to the 3 groups (ET [n = 18], MT [n = 18], and CT [n = 20]). During the 10-week intervention 3 individuals dropped from both ET and MT groups, resulting in 50 patients completing the study. Results demonstrated that the 3 groups were not different in age, anthropometrics, resting BP, or chronotype. Both groups improved VO₂ and did not reduce body weight following the exercise intervention.

Results for resting BP and SVR in the morning session were lower measures in both the ET and MT group when compared to the control group. Resting morning systolic BP and SVR had the greatest reductions in the ET group. Following evening measures, only the ET group's systolic BP was significantly reduced when compared to the MT and CT groups. There were no significant differences in evening resting BP between the MT and CT group. Resting diastolic BP reductions were observed in the ET group in both the morning and evening measures; however, neither measure was significantly different when compared to the MT and CT group. There were no changes in cardiac output for any of the groups.

CLINICAL IMPLICATIONS

This is the first study to investigate the effects of chronic aerobic training in the evening versus morning for BP reduction in men prescribed antihypertension medication. The major findings of this study were that aerobic exercise in the evening resulted in significant reductions in systolic BP and SVR when compared to morning training. Both evening and morning training resulted in improved cardiorespiratory fitness, reductions in resting BP, and reductions in resting heart rate when compared to the control group. The findings of this study exemplify the importance of physical activity and exercise as a complimentary method to manage BP. If it is feasible, clinical exercise physiologists should encourage evening exercise training in this type of persons. Additionally, the clinical exercise physiologist should remind all patients that exercise at any time of day is better than a sedentary lifestyle based on the overall health-related benefits. Further research needs to be conducted with females, different intensity levels, and types of exercise (i.e., resistance training).

MANUSCRIPT REVIEW

The purpose of this study was to investigate if intestinal temperatures (T_INT) via telemetric pills, and esophageal temperatures (T_ESO) provide comparable temperature information during upper body aerobic exercise in untrained men with paraplegia and tetraplegia. The authors of the study hypothesized that both T_INT and T_ESO would provide similar core temperature measures in persons with SCI. Males living in Wakayama, Japan were recruited to participate in this cross-sectional study. Seventeen individuals (12 with SCI [5 paraplegic and 7 tetraplegic] and 5 non-SCI) agreed to participate in the study and reported to the laboratory for 2 separate visits.

During session 1, patients underwent autonomic testing and performed an upper body ergometer graded exercise test (GXT). Autonomic function was assessed by sympathetic skin response (SSR), which used progressively increasing electrical stimuli (12–20mA) until a motor response was elicited (8), and orthostatic hypertension (OH) was assessed by the sit up test. Time to motor response for the SSR was used to determine severity of autonomic dysfunction (8). OH was defined as ≥ 20 mm Hg or ≥ 10 mm Hg drop in systolic or diastolic blood pressure following the shift in body position for the sit up test. For the GXT, all patients cycled on an arm ergometer at 50 r·min⁻¹ with increasing workload until the participant's cycle cadence fell below 40 r·min⁻¹. Expired gas was collected during the GXT to determine peak VO₂.

For session 2, each patient performed two 15-min bouts of upper body cycling at 50% peak VO₂ with a 2-min rest between each bout. During the cycling ECG, blood pressure, skin temperature (measured at 10 sites), T_INT (measured via telemetric pill), and T_ESO (measured by esophageal probe) were continuously monitored. Telemetric pills were ingested 8 to10 h prior to the exercise session and the esophageal probe was inserted through the right nostril and placed at the level of the right atria. Heat storage was calculated by using skin temperature and T_INT or T_ESO measures.

Baseline testing demonstrated that patients with tetraplegia had an absence of SSR and were positive for OH, where paraplegic patients maintained SSR of the upper limbs while none tested positive for OH. As anticipated, all control patients had a normal SSR and 1 control tested positive for OH. For exercise responses, men with SCI both had significantly lower peak VO₂ and workload when compared to control patients during the GXT as well as both bouts of arm cycling.

At rest, there were no significant differences in T_INT or T_ESO between groups. T_ESO had a significantly lower temperature at rest compared to T_INT. T_ESO and T_INT measures showed consistent rise in temperature between the paraplegic and control groups when comparing baseline to the 2 exercise bouts. There was no change in T_ESO and T_INT for the tetraplegic group. T_ESO temperatures began rising ~ 7 min earlier in both exercise bouts when compared to T_INT. There was no increase in skin temperature from baseline in any of the groups for either bout of exercise. The tetraplegia group had a time x group interaction with a reduction in forearm temperature as time progressed in each bout of exercise. Heat storage only increased when estimated from T_ESO for the paraplegic and control groups in the first 15-min bout of exercise. For the second bout of exercise, only the paraplegic group had a heat storage increase when compared to the first bout of exercise.

CLINICAL IMPLICATIONS

Results of the study confirm that persons with SCI have difficulty with thermoregulation when compared to non-SCI patients. With regard to monitoring core temperature, both T_ESO and T_INT responded similarly in the paraplegic and non-SCI groups. Neither method was appropriate for measuring core temperature in persons with tetraplegia. For convenience of monitoring, the clinical exercise physiologist may consider measuring clients with paraplegia via telemetric pill, which are typically well tolerated and inexpensive as compared to other methods. This is especially important when exercise takes place in an environment that may increase heat storage (e.g., GXT session or outdoor charity run/walk during hot and humid weather conditions).

Findings of this study are limited to men under controlled exercise intensities and laboratory climate. Further research is required to determine if the findings of this study are consistent with females, different age groups, and modes of exercise.