**1. Introduction**

Physical fitness is an integrated measure of all the functions and structures involved in performing physical activity [1]. Nowadays, physical fitness is one surrogate marker of overall adult health (19–64 years), especially cardiorespiratory fitness and muscular strength. Cardiorespiratory fitness is inversely associated with cardiovascular diseases [2], obesity [3], osteoporosis [4] diabetes [5], different cancer types [6,7], and is a predictor of all-cause of mortality [8–12] and cardiovascular disease [10,12–15]. Likewise, in the psychological sphere, high levels of cardiorespiratory fitness are associated with well-being [16,17], improved cognitive function [18] and a reduced risk of Alzheimer's disease [19] and other mental conditions such as anxiety, panic and depression [20]. Muscular strength demonstrates a protective effect against all-cause mortality [21,22]; and is inversely associated

**Citation:** Castro-Piñero, J.;

Marin-Jimenez, N.; Fernandez-Santos, J.R.; Martin-Acosta, F.; Segura-Jimenez, V.; Izquierdo-Gomez, R.; Ruiz, J.R.; Cuenca-Garcia, M. Criterion-Related Validity of Field-Based Fitness Tests in Adults: A Systematic Review. *J. Clin. Med.* **2021**, *10*, 3743. https:// doi.org/10.3390/jcm10163743

Academic Editors: David Rodríguez-Sanz and Naama W. Constantini

Received: 8 June 2021 Accepted: 15 August 2021 Published: 23 August 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

with weight gain and adiposity-related hypertension occurrence and the prevalence and incidence of the metabolic syndrome, [22] and mental health clinical presentations [23,24]. Consequently, physical fitness assessment is a vital tool of prevention and health diagnoses.

Laboratory testing is an objective and accurate method of assessing physical fitness. However, due to the cost of sophisticated instruments, time constraints and the need for qualified technicians, laboratory testing is limited to sport clubs, schools, population-based studies, and offices or clinical settings. However, field-based fitness testing can offer useful and practical alternatives as screening tools, since they are relatively safe and time-efficient, involve minimal equipment and low cost, and can be easily administered to multiple people simultaneously.

The validity of field-based fitness tests needs to be considered when deciding which test to use [25]. Criterion-related validity refers to the extent to which a field-based test of a physical fitness component correlates with the criterion measure (i.e., the gold standard) [26]. Since the early interest in physical fitness testing in the 1950–1960s, many field-based fitness tests have been proposed [27]. It would be desirable to summarise the criterion-related validity of the existing field-based fitness tests in adults. There have been attempts to summarize the criterion-related validity of a certain test [28,29] or several tests with a common characteristic [30–32]; however, no attempts have been made to summarise the criterion-related validity of all the existing field-based fitness tests in adults.

Therefore, the aim of the present systematic review was to comprehensively study the criterion-related validity of the existing field-based fitness tests used in adults. The findings of this review will provide an evidence-based proposal for most valid field-based fitness tests for healthy adults, aged 19–64 years old.

### **2. Materials and Methods**

The review was registered in PROSPERO (registration number: CRD42019118482) and the applied methodology followed the guidelines drawn in the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement [33].
