## 3 Results
### Main Findings  
Most studies, i.e., 73%, did not report any veracity metric for all the identified parameters (n = 69). At least one veracity metric was reported in 18% of studies (n = 17), with a veracity metric for all parameters reported in 9% of studies (n = 8; see Figure 77). Thirty-nine different tools were used for load monitoring: electronic performance tracking systems (EPTS) = 64% (n = 60), rating of perceived exertion (RPE) = 48% (n = 45), heart rate monitoring (HR) = 29% (n = 27), countermovement jump test (CMJ) = 12% (n = 11), psychometric questionnaire with Likert scale = 12% (n = 11), blood samples = 6% (n = 6), maximal running test = 6% (n = 6), salivary mumoglobulins A (s-IgG) = 6% (n = 6), blood lactate concentration = 5% (n = 5), video-computerized systems = 5% (n = 5), watch = 5% (n = 5), body composition = 3% (n = 3), integrative tool of training load assessment = 3% (n = 3), repeated sprint ability = 3% (n = 3), salivary cortisol = 3% (n = 3), salivary testosterone = 3% (n = 3), submaximal running test = 3% (n = 3), sprint test = 3% (n = 3), anaerobic speed reserve = 2% (n = 2), creatine kinase (CK) = 2% (n = 2), maximal oxygen uptake = 2% (n = 2), Visual Analog Scale Questionnaire = 2% (n = 2), total quality recovery (TQR) = 2% (n = 2), training planning = 2% (n = 2), actigraphy = 1% (n = 1), blood ammonia concentration = 1% (n = 1), coach rating of performance = 1% (n = 1), Edinburgh Mental Well-being Scale = 1% (n = 1), infrared thermography = 1% (n = 1), isometric force testing = 1% (n = 1), Neuro-muscular Efficiency Index = 1% (n = 1), oxidative stress = 1% (n = 1), Physical Activity Enjoyment Scale = 1% (n = 1), Profile of Mood State Questionnaire (POMS) = 1% (n = 1), RESTQ-Sport Scale = 1% (n = 1), sit-and-reach test = 1% (n = 1), squat jump test (S)) = 1% (n = 1), tensiomyography = 1% (n = 1), and urine metabolomic = 1% (n = 1).  
Figure 1: Study selectionin a PRISMA flow diagram.  
A total of 578 parameters were used to monitor the load from these 39 tools. Data veracity was reported for 54% of the tools in at least one parameter, which resulted in 23% of these parameters. Thus, most studies did not report metrics of veracity for their tools and parameters (see details in Figure 1, Table 1 and Table S2). Specifically, Table S2 presents a summary of all the selected studies, with further information on study design (and duration), sample level (n; sex; age; country of sample), tools (brand and model or reference), accuracy reported by the company, and parameters as well as veracity analyses (metrics).  
Figure 2: Veracity metrics classifications.Median (minimum–maximum) and result (i.e., median) without range (i.e., minimum and maximum) because it was found just for one value (n = 1). Based on the current method, the respective reference values were used in this figure to determine the traffic-light systems (i.e., red, amber, or green). The median was used to  
determine the color, and blank cells are due to the lack of veracity metrics for that case. CV = coefficient of variation (standard deviation divided by the mean, expressed as a percentage, %); ICC = intraclass correlationcoefficient; SEM = standard error of measurement; EPTS = electronic performance tracking system; RPE = rating of perceived exertion; HR = heart rate; CMJ = countermovement jump; Psychom Quest = Psychometric Questionnaire with Likert scale; S-IgA = salivary imunoglobulin A; S-Cortisol = salivary cortisol; S-Testosterone = salivary testosterone; CK = creatine kinase; MRT = maximal running test; RSA = repeated sprint ability; TQR = total quality recovery; IF = isometric force; POMS = Profile of Mood State Questionnaire; SJ = squat jump; Watch = wristwatch.