*3.1. Quality Assessment*

Of the 101 original studies included in the present systematic review, 11 and 40 studies were classified as very low (a total score less than 2) and low quality (a total score of 3 and 4), respectively (see Supplementary Table S3). A total of 50 original studies were classified as high-quality (a total score higher than 4). Of these 40, nine and one analysed the criterionrelated validity of cardiorespiratory fitness, muscular strength and flexibility field-based fitness tests in adults, respectively. No study of those classified as high quality analysed the criterion-related validity of motor fitness (i.e., speed, agility, balance and coordination).

Two meta-analyses [28,30] and one systematic review [32] were ranked as high quality (all eight points), and two meta-analyses [29,31] were ranked as medium quality (both seven points) (see Supplementary Table S2). Three of them assessed the criterion-related validity of field-based cardiorespiratory fitness tests: the 20 m shuttle run test [28]; distance and time-based run/walk tests [30]; and the step tests [32]—whilst and two of them studied the criterion-related validity of the sit-and-reach [31] and toe-to-touch tests [29].

\* References of high-quality studies are presented in Supplementary Material 3.

### *3.2. Criterion-Related Validity*

Table 1 shows a summary of the different levels of evidence found for the criterionrelated validity of cardiorespiratory fitness tests.

**Table 1.** Levels of evidence of cardiorespiratory fitness tests.



**Table 1.** *Cont*.

Indicates high validity; moderate validity; low/null validity; inconclusive validity.

#### 3.2.1. Cardiorespiratory Fitness
