Purpose <p>Physical fitness (PF) is a&#xa0;health and performance indicator. Test batteries such as Diagnoform® assess PF, but despite increasing attention, the validity and training response of four Diagnoform® tests remain unverified. This cohort study aimed to evaluate the indirect concurrent validity and training response of four Diagnoform® tests: a&#xa0;3-min shuttle run (3-MSR), a&#xa0;cross test, a&#xa0;modified plank test, and a&#xa0;modified unipedal stance test.</p> Methods <p>A&#xa0;total of 65 runners completed four Diagnoform® and four reference tests. Cardiorespiratory fitness (CRF) was assessed using the 3‑MSR and an incremental intermittent field test (45-15_FIT). Agility was tested with the cross and hexagon agility tests. Muscular endurance (ME) was assessed with the modified plank and sport-specific endurance plank tests, and balance via modified and standard unipedal stance tests. Concurrent validity was examined using bivariate correlations. Training response was assessed by comparing within-test performance changes and by classifying individual responses using the smallest worthwhile change (SWC). Bowker’s test of symmetry compared the distribution of runners across response categories between the Diagnoform® and reference tests.</p> Results <p>Correlation was very high for CRF (<i>r</i> = 0.932), moderate for agility (<i>r</i> = 0.502), high for ME (<i>r</i> = 0.716), and significant but low for balance (<i>p</i> = 0.003, <i>r</i> = 0.376). No statistical differences in performance changes or response-category distributions were observed, except for CRF tests, where a&#xa0;difference in distribution was reported (<i>p</i> = 0.047).</p> Conclusion <p>These results suggest that the Diagnoform® tests may provide indicators of validity and training response in healthy adults.</p>