Effect of Moderate- Versus High-Intensity Interval Exercise Training on Heart Rate Variability Parameters in Inactive Latin-American Adults: A Randomized Clinical Trial.

Ramírez-Vélez, R, Tordecilla-Sanders, A, Téllez-T, LA, Camelo-Prieto, D, Hernández-Quiñonez, PA, Correa-Bautista, JE, Garcia-Hermoso, A, Ramírez-Campillo, R, and Izquierdo, M. Effect of moderate- versus high-intensity interval exercise training on heart rate variability parameters in inactive Latin-American adults: a randomized clinical trial. J Strength Cond Res 34(12): 3403-3415, 2020-We investigated the effect of moderate versus high-intensity interval exercise training on the heart rate variability (HRV) indices in physically inactive adults. Twenty inactive adults were randomly allocated to receive either moderate-intensity training (MCT group) or high-intensity interval training (HIT group). The MCT group performed aerobic training at an intensity of 55-75%, which consisted of walking on a treadmill at 60-80% of the maximum heart rate (HRmax) until the expenditure of 300 kcal. The HIT group ran on a treadmill for 4 minutes at 85-95% peak HRmax and had a recovery of 4 minutes at 65% peak HRmax until the expenditure of 300 kcal. Supine resting HRV indices (time domain: SDNN = SD of normal-to-normal intervals; rMSSD = root mean square successive difference of R-R intervals and frequency domain: HFLn = high-frequency spectral power; LF = low-frequency spectral power and HF/LF ratio) were measured at baseline and 12 weeks thereafter. The SDNN changes were 3.4 (8.9) milliseconds in the MCT group and 29.1 (7.6) milliseconds in the HIT group {difference between groups 32.6 (95% confidence interval, 24.9 to 40.4 [p = 0.01])}. The LF/HFLn ratio changes were 0.19 (0.03) milliseconds in the MCT group and 0.13 (0.01) milliseconds in the HIT group (p between groups = 0.016). No significant group differences were observed for the rMSSD, HF, and LF parameters. In inactive adults, this study showed that a 12-week HIT training program could increase short-term HRV, mostly in vagally mediated indices such as SDNN and HF/LFLn ratio power. Trial registration. ClinicalTrials.gov NCT02738385 https://clinicaltrials.gov/ct2/show/NCT01796275, registered on March 23, 2016.

Acute Effects of High Intensity, Resistance, or Combined Protocol on the Increase of Level of Neurotrophic Factors in Physically Inactive Overweight Adults: The BrainFit Study.

The purpose of this study was to compare the neurotrophic factor response following one session of high-intensity exercise, resistance training or both in a cohort of physically inactive overweight adults aged 18-30 years old. A randomized, parallel-group clinical trial of 51 men (23.6 ± 3.5 years; 83.5 ± 7.8 kg; 28.0 ± 1.9 kg/m2) who are physically inactive (i.e., < 150 min of moderate-intensity exercise per week or IPAQ score of <600 MET min/week for >6 months) and are either abdominally obese (waist circumference ≥90 cm) or have a body mass index, BMI ≥25 and ≤ 30 kg/m2 were randomized to the following four exercise protocols: high-intensity exercise (4 × 4 min intervals at 85-95% maximum heart rate [HRmax] interspersed with 4 min of recovery at 75-85% HRmax) (n = 14), resistance training (12-15 repetitions per set, at 50-70% of one repetition maximum with 60 s of recovery) (n = 12), combined high-intensity and resistance exercise (n = 13), or non-exercising control (n = 12). The plasma levels of neurotrophin-3 (NT-3), neurotrophin-4 (also known as neurotrophin 4/5; NT-4 or NT-4/5), and brain-derived neurotrophic factor (BDNF) were determined before (pre-exercise) and 1-min post-exercise for each protocol session. Resistance training induced significant increases in NT-3 (+39.6 ng/mL [95% CI, 2.5-76.6; p = 0.004], and NT-4/5 (+1.3 ng/mL [95% CI, 0.3-2.3; p = 0.014]), respectively. Additionally, combined training results in favorable effects on BDNF (+22.0, 95% CI, 2.6-41.5; p = 0.029) and NT-3 (+32.9 ng/mL [95% CI, 12.3-53.4; p = 0.004]), respectively. The regression analysis revealed a significant positive relationship between changes in BDNF levels and changes in NT-4/5 levels from baseline to immediate post-exercise in the combined training group (R2 = 0.345, p = 0.034) but not the other intervention groups. The findings indicate that acute resistance training and combined exercise increase neurotrophic factors in physically inactive overweight adults. Further studies are required to determine the biological importance of changes in neurotrophic responses in overweight men and chronic effects of these exercise protocols. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02915913 (Date: September 22, 2016).