Inter-Individual Differences in Cognitive Response to a Single Bout of Physical Exercise-A Randomized Controlled Cross-Over Study

Abstract

Recent reviews have shown that acute exercise can improve cognitive functions, especially executive functions. However, a closer look at the included studies revealed a wide inter-individual variability in the effects of exercise on cognition. Therefore, thirty-nine healthy adults (age: 19-30 years) were analyzed in a randomized, controlled cross-over study with two exercise groups (n = 13 each) and a sedentary control group (n = 13). The exercise conditions included moderate (30 min at 40-59% VO_2max) and high intensity interval (five × 2 min at 90% VO_2max with 3 min active recovery at 40% VO_2max) treadmill exercise. The main outcome assessed was cognitive performance (attention, inhibitory control, cognitive flexibility) and underlying inter-individual variability in young adults. On the group level no significant group or group × time interaction effects were observed. Using a median split, we found significant differences between low and high cognitive performers regarding cognitive function following moderate and high intensity interval treadmill exercise. Furthermore, using a pre-determined threshold we could identify responders and non-responders to acute exercise. Therefore, future research should consider individual performance requirements.

Keywords: acute exercise; cognition; lactate; personalized medicine; responder.

Figure 1

Experimental design. N = 39. Study included three sessions (t0, t1, t2) and three groups: experimental group 1 (EG1, n = 13), experimental group 2 (EG2, n = 13) and control group (CG, n = 13). The experimental groups performed either a single bout of moderate intensity or a high-intensity interval training (hiit) while the control group was sedentary. Main outcome variable was cognitive performance.

Figure 2

Both physical exercise conditions lasted 35 min each. Single session physical exercise in moderate intensity: 30 min at 40–59% VO_2max and 5 min warm up at 40% VO_2max. Single session high intensity interval training (hiit): 5 min warm up at 40% VO_2max, 5 two-minute periods at 90% VO_2max each followed by three-minute recovery periods at 40% VO_2max and a cool down at 40% VO_2max.

Figure 3

Parameters of the incremental step test at baseline. (A) Maximal oxygen uptake (VO_2max) as a parameter for individual cardiovascular fitness and (B) max. lactate concentration (mmol/L) as a parameter for metabolic response. EG1 (experimental group 1, n = 13), EG2 (experimental group 2, n = 13), CG (control group, n = 13). Error bars represents the mean ± one standard deviation.

Figure 4

Amount of the blood lactate concentration post-pre-value (mmol/L) for moderate (n = 26) and hiit (n = 26) exercise condition, ** p < 0.001. Error bars represents the mean ± one standard deviation.

Figure 5

Post-hoc tests for cognitive composite score (A): moderate condition, (B): hiit condition. LCP = low cognitive performance (n = 13), HCP = high cognitive performance (n = 13), CG = control group (n = 13). A positive value reflects greater cognitive performance. * p < 0.05, ** p < 0.001. Error bars represents the mean ± one standard deviation.

Figure 6

Post-hoc tests for TMT-B exemplary (reaction time in seconds). (A): moderate condition, (B): hiit condition. LCP = low cognitive performance (n = 13), HCP = high cognitive performance (n = 13), CG = control group (n = 13). Lower reaction time reflects greater cognitive performance. * p < 0.05, ** p < 0.001. Error bars represents the mean ± one standard deviation.

Figure 7

Cognitive performance (percentile rank) for baseline and after each intensity. Exemplary for a high cognitive performer (A) and a low cognitive performer (B) of the experimental group. Cognitive test variables including d2-R (F%, BZO), Stroop task reading condition (S-read.) and naming condition (S-nam.) and TMT (TMT-A, TMT-B). Green line: t0 (baseline), blue line: moderate condition, red line: hiit condition. The higher the net the higher the cognitive performance.

Figure 8

Individual response calculated with SWC (0.2 × between-standard deviation) and 50% CI (pre-post change ± typical error) for all subjects of the experimental groups (n = 26) for TMT-B moderate (left) and hiit (right) condition. Green bars labels responder (true score change CI above SWC), the grey area marks non-responder. The other subjects are divided into potential responder with true score change above SWC but below CI (yellow bars) and non-responder with true change score CI below SWC (red bars). Positive value reflects an increase of cognitive performance, a negative value vice versa.