Neurophysiological Markers for Monitoring Exercise and Recovery Cycles in Endurance Sports

Abstract

The current study analyzes the suitability and reliability of selected neurophysiological and vegetative nervous system markers as biomarkers for exercise and recovery in endurance sport. Sixty-two healthy men and women, endurance trained and moderately trained, performed two identical acute endurance tests (running trial 1 and running trial 2) followed by a washout period of four weeks. Exercise protocol consisted of an acute running trial lasting 60 minutes. An intensity corresponding to 95% of the heart rate at individual anaerobic threshold for 40 minutes was followed by 20 minutes at 110%. At pre-exercise, post-exercise, three hours post-exercise and 24 hours post-exercise, experimental diagnostics on Brain-derived neurotrophic factor (BDNF), heart rate variability (HRV), Stroop Color and Word Test (SCWT), and Short-Form McGill Pain Questionnaire (SF-MPQ) were performed. Significant changes over time were found for all parameters (p < .05). Furthermore, there was an approached statistical significance in the interaction between gender and training status in BDNF regulation (F₍₃₎ = 2.43; p = 0.06), while gender differences were found only for LF/HF-ratio (3hPoEx, F₍₃₎ = 3.40; p = 0.002). Regarding the reliability, poor ICC-values (< 0.5) were found for BDNF, Stroop sensitivity and pNN50, while all other parameters showed moderate ICC-values (0.5-0.75). Plasma-BDNF, SCWT performance, pain perception and all HRV parameters are suitable exercise-sensitive markers after an acute endurance exercise. Moreover, pain perception, SCWT reaction time and all HRV parameters show a moderate reliability, others rather poor. In summary, a selected neurophysiological and vegetative marker panel can be used to determine exercise load and recovery in endurance sports, but its repeatability is limited due to its vaguely reliability.

Keywords: NNervous system; biomarkers; executive function; heart rate variability; monitoring training; reliability.

Figure 1.

Plasma BDNF concentration (A), total score of SF-MPQ (B), and Stroop Test parameters (C – E) PrEx, PoEx, 3hPoEx and 24hPoEx for both RTs. Significant differences *(p < 0.05) to the previous MTP as well as significant differences #(p < 0.05) to the PrEx value. Values are means (±SD).

Figure 2.

Changes in time domain HRV parameters PoEx, 3hPoEx, and 24hPoExat both RTs. *(p < 0.05) to the previous MTP as well as significant differences #(p < 0.05) to the PreExvalue. Values are means (±SD).

Figure 3.

Changes in frequency domain HRV parameters PoEx, 3hPoEx, and 24hPoEx at both RTs. *(p < 0.05) to the previous MTP as well as significant differences #(p < 0.05) to the PrEx value. Values are means (±SD).

Figure 4.

Correlations between IL-8 and VLF in men at both RTs in recovery phase after RTs. (A1) shows the recovery response of RT1, (A2) of RT2. Differences between the MTPs were used for the analyses. Significant correlations are presented with p < 0.05, n = 23.

Figure 5.

Correlations in moderately trained individuals (n = 14/ 18) (B1/2: IL-1ra and SF-MPQ total score, RT1; C1/2: IL-6 and SD2, RT2; D1/2: IL-8 and pNN50, RT2) at the exercise and recovery response on one RT. Number one of the graphs show the results of the exercise response, number two those of the recovery response. Differences between the MTPs were used for the analyses. Significant correlations are presented with p < 0.05.