Short-Term Effects of Anodal Transcranial Direct Current Stimulation on Endurance and Maximal Force Production. A Systematic Review and Meta-Analysis

Abstract

The purpose of the present systematic review and meta-analysis was to explore the effects of transcranial direct current stimulation (tDCS) on endurance (i.e., time to task failure (TTF)) and maximal voluntary contraction (MVC). Furthermore, we aimed to analyze whether the duration of stimulation, the brain region targeted for stimulation, and the task performed could also influence motor performance. We performed a systematic literature review in the databases MEDLINE and Web of Science. The short-term effects of anodal tDCS and sham stimulation (placebo) were considered as experimental and control conditions, respectively. A total of 31 interventions were included (MVC = 13; TTF = 18). Analysis of the strength-related tDCS studies showed small improvements in the MVC (SMD = 0.19; 95% CI = -0.02, 0.41; p = 0.08). However, the results of the endurance-related interventions indicated a moderate effect on TTF performance (SMD = 0.26; 95% CI = 0.07, 0.45; p = 0.008). Furthermore, the sub-analysis showed that anodal tDCS over M1 and stimulation durations longer than 10 min produced the best results in terms of TTF performance enhancement. Additionally, the effects of anodal tDCS were larger during full body exercises (i.e., cycling) when compared to uniarticular tasks. In conclusion, the current meta-analysis indicated that anodal tDCS leads to small and moderate effects on MVC and TTF, respectively.

Keywords: Non-invasive brain stimulation; maximal voluntary contraction; prefrontal cortex; primary motor cortex; time to task failure.

Figure 1

Flow diagram of the literature search.

Figure 2

Forest plot of the comparison of MVC between anodal tDCS and sham conditions. Angius et al. [27] $—condition in which the subjects received anodal tDCS using a cephalic montage (Anode in M1 and Cathode in right DLPFC). Angius et al. [27] @—condition in which the subjects received anodal tDCS using an extracephalic montage (Anode in M1 and Cathode in shoulder).

Figure 3

Forest plot of the comparison of TTF between anodal tDCS and sham conditions. Williams et al. [17] *—subgroup that received full time anodal tDCS during the task (i.e., submaximal isometric elbow contraction until failure). Williams et al. [17] #—subgroup that received part time anodal tDCS during the task (i.e., submaximal isometric elbow contraction until failure). Angius et al. [27] *—condition in which the subjects received anodal tDCS using a cephalic montage (Anode in M1 and Cathode in right DLPFC). Angius et al. [27] #—condition in which the subjects received anodal tDCS using an extracephalic montage (Anode in M1 and Cathode in shoulder). Radel et al. [16] *—condition in which the subjects received anodal tDCS over the PFC. Radel et al. [16] #—condition in which the subjects received anodal tDCS over the M1.

Figure 4

Forest plot of the subgroup analysis for the comparison of the TTF between anodal tDCS over M1 versus PFC. Williams et al. [17] *—subgroup that received full time anodal tDCS during the task (i.e., submaximal isometric elbow contraction until failure). Williams et al. [17] #—subgroup that received part time anodal tDCS during the task (i.e., submaximal isometric elbow contraction until failure). Angius et al. [27] *—condition in which the subjects received anodal tDCS using a cephalic montage (Anode in M1 and Cathode in right DLPFC). Angius et al. [27] #—condition in which the subjects received anodal tDCS using an extracephalic montage (Anode in M1 and Cathode in shoulder). Radel et al. [16] *—condition in which the subjects received anodal tDCS over the PFC. Radel et al. [16] #—condition in which the subjects received anodal tDCS over the PFC.

Figure 5

Forest plot of the subgroup analysis for the comparison of the TTF between anodal tDCS applied ≤10 min. versus >10 min. Williams et al. [17] *—subgroup that received full time anodal tDCS during the task (i.e., submaximal isometric elbow contraction until failure). Williams et al. [17] #—subgroup that received part time anodal tDCS during the task (i.e., submaximal isometric elbow contraction until failure). Angius et al. [27] *—condition in which the subjects received anodal tDCS using a cephalic montage (Anode in M1 and Cathode in right DLPFC). Angius et al. [27] #—condition in which the subjects received anodal tDCS using an extracephalic montage (Anode in M1 and Cathode in shoulder). Radel et al. [16] *—condition in which the subjects received anodal tDCS over the PFC. Radel et al. [16] #—condition in which the subjects received anodal tDCS over the PFC.

Figure 6

Forest plot of the subgroup analysis for the comparison of the effects of anodal tDCS on TTF between studies that used whole-body (i.e., cycling) versus uniarticular (i.e., submaximal isometric contractions until failure) tasks. Williams et al. (2013) *—subgroup that received full time anodal tDCS during the task (i.e., submaximal isometric elbow contraction until failure). Williams et al. (2013) #—subgroup that received part time anodal tDCS during the task (i.e., submaximal isometric elbow contraction until failure). Angius et al. (2016) *—condition in which the subjects received anodal tDCS using a cephalic montage (Anode in M1 and Cathode in right DLPFC). Angius et al. (2016) #—condition in which the subjects received anodal tDCS using an extracephalic montage (Anode in M1 and Cathode in shoulder). Radel et al. (2017) *—condition in which the subjects received anodal tDCS over the PFC. Radel et al. (2017) #—condition in which the subjects received anodal tDCS over the PFC.