Cerebral Hemodynamic and Neurotrophic Factor Responses Are Dependent on the Type of Exercise

Figures

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  FIGURE 1. Participants took part in three separate exercise visits in a randomized order, consisting of 30 min of moderate, steady-state exercise at 65% VO2peak (MICT); four 4 min high intensity intervals at 85% HRmax (HIIT); and four 30 s supramaximal sprint intervals at 200% Wmax (SIT). All protocols were preceded by 5 min of seated rest and a 5 min warm-up, and followed by 3 min of active recovery at 50 W and 15 min of seated passive recovery. The timing of blood sampling (red droplet), data averaging windows, and labels for analysis (green boxes) and the period used in area under the curve (AUC) analysis (pink bracket) are included for all protocols. Averaging was carried out over 30-second windows across the course of each exercise protocol (Ex) and during the initial and final minute of recovery (Reco) following each HIIT and SIT bout. The final 30-second recovery window in both HIIT and SIT was taken as the active recovery timepoint, in conjunction with the active recovery window (Active) in MICT. VO2peak, maximum oxygen consumption; HRmax, maximum heart rate; Wmax, maximum aerobic power.

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  FIGURE 2. (A) MCAv was determined continuously by transcranial doppler ultrasound (TCD) and presented as change in MCAv from rest in each protocol for each participant. (B) PETCO2 was determined through breath-by-breath respiratory gas exchange and ventilation. Data were averaged over 30 s of rest (rest); 5 min warm up (warm up); 3 min active recovery (active); and 15 min seated passive recovery (passive) in all protocols. Exercising averages (Ex 1–4) were taken every 7 min during 30 min of moderate intensity (65% VO2peak) steady state exercise (MICT); in the final minute of the four 4 min high intensity (85% HRmax) interval bouts (HIIT) and across the duration of four 30 s supramaximal (200% Wmax) sprint intervals (SIT). Data are presented as mean ± SD (n = 24; except SIT–Passive: n = 23) and were analyzed by linear mixed models. Significant differences (analyzed by linear mixed model, p < 0.05) between resting values and subsequent time points are denoted by *. Significant differences between protocols are denoted by $ between MICT and HIIT; † between MICT and SIT; and Ω between HIIT and SIT.

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  FIGURE 3. (A) MCAv was determined continuously by transcranial doppler ultrasound (TCD) and presented as change in MCAv from rest in each protocol for each participant. (B) PETCO2 was determined by measurement of breath-by-breath respiratory gas exchange and ventilation. Data were averaged for 1 min during seated rest (Rest); over 30 s during the final minute of four 4 min high intensity (85% HRmax) interval bouts (HIIT; Ex 1 – 4); across the duration of four 30 s supramaximal (200% Wmax) sprint intervals (SIT; Ex 1 – 4), and over a 30 s period, 15 s into the recovery following each bout in both interval protocols (Reco 1 – 4). Data are presented as mean ± SD (n = 24). Significance (analyzed by linear mixed model, p < 0.05) between time points is denoted by * for differences from resting values; € for differences between interval (ex) and recovery (reco). Significant differences between protocols are denoted by Ω.

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  FIGURE 4. MCAv was determined continuously by transcranial doppler ultrasound (TCD) and exported at 1 Hz frequency from the onset of each protocol after warm-up had been completed. Exercise protocols were: 30 min of moderate intensity (65% VO2peak) steady state exercise (MICT); four 4 min high intensity (85% HRmax) interval bouts (HIIT) separated by 3 min active recovery at 50 W and four 30 s supramaximal (200% Wmax) sprint intervals (SIT) separated by 4.5 min active recovery at 50 W, with all protocols followed by 3 min of active recovery at 50 W. Data are presented as average ± 95% confidence intervals (n = 18), across the duration of each protocol including active recovery periods, with resting values averaged over 30 s of seated rest presented for comparison. These time periods were identical to those used in calculation of area under the curve (AUC). Continuous effort during MICT and the timing of the four interval periods in HIIT and SIT are highlighted in pink.

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  FIGURE 5. Blood plasma samples were taken during seated rest (Rest); immediately after the first interval exercise bout (Ex 1; HIIT and SIT only); at the end of exercise (Ex 4, end of active recovery (Active); and the end of passive recovery (Passive). Brain-derived neurotrophic factor (BDNF; n = 21), insulin-like growth factor 1 (IGF-1; n = 17), and vascular endothelial growth factor [VEGF; n = 15 (14 in SIT)] were analyzed by ELISA. Blood lactate [n = 24 (23 in SIT)] was analyzed using automated photometric analysis. Data are presented as mean ± SD. Significance (analyzed by linear mixed model, p < 0.05) between resting values and subsequent time points is denoted by *. Significant differences between protocols are denoted by $ between MICT and HIIT; † between MICT and SIT; and Ω between HIIT and SIT. ND, not determined.

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  FIGURE 6. Blood plasma samples were taken were taken during seated rest (Rest); immediately after the first interval exercise bout (Ex 1; HIIT and SIT only); at the end of exercise (Ex 4); end of active recovery (Active)’ and end of passive recovery (Passive). Brain-derived neurotrophic factor (BDNF; n = 21, 7 female) was analyzed by ELISA. Data are presented as mean ± SD. Significance (analyzed by linear mixed model, p < 0.05) between resting values and subsequent time points is denoted by *. Significant differences between sexes at a given time point are denoted by §. M, Male; F, Female; ND, not determined.