Exploring the Validity of the Velocity Matters Linear Position Transducer in the Back Squat and Bench Press.

Pearson's correlation between Velocity Matters and GymAware ranged from good to excellent across all velocity ranges and exercises.

• Pearson's r values ranged from 'good (0.5-0.7) to excellent (>0.9) correlations across all ranges and exercises'
• Correlations were assessed for both mean velocity (MV) and peak velocity (PV) in back squat (SQ) and bench press (BP)
• 15 male participants completed two testing sessions with 180 repetitions per velocity range analyzed for each exercise

Acceptable mean absolute error (MAE) values were found only for mean velocity in back squat (except at >1.00 m·s-1) and for both mean and peak velocity in bench press at velocities below 0.70 m·s-1.

• MAE was acceptable for MV in SQ across velocity ranges 2–5 (0.51–0.99 m·s-1) but not at the highest velocity range (>1.00 m·s-1)
• In BP, acceptable MAE was limited to both MV and PV only at velocities <0.70 m·s-1 (velocity ranges 4 and 5: 0.40–0.69 m·s-1)
• MAE was not acceptable for PV in SQ across all velocity ranges tested

Bland-Altman analyses revealed systematic underestimation by Velocity Matters with wide limits of agreement even in cases where MAE was acceptable.

• Systematic underestimation by Velocity Matters was observed across all velocity ranges and both exercises
• Limits of agreement were 'wide' with values of up to -0.08 m·s-1 in SQ and -0.09 m·s-1 in BP
• Wide limits of agreement persisted 'even where MAE was acceptable', indicating practical limitations beyond what MAE alone suggests

Intraclass correlation coefficient (ICC) values were generally above 0.70 but showed wide confidence intervals indicating high uncertainty.

• ICC values were 'generally >0.70' across velocity ranges and both exercises
• Wide confidence intervals accompanied ICC values, indicating 'high uncertainty' in the reliability estimates
• ICC values above 0.70 alone were insufficient to confirm acceptable validity given the accompanying uncertainty

Concordance correlation coefficient (CCC) values were consistently poor across almost all conditions for both exercises.

• CCC values were 'consistently poor (<0.90) across all velocity ranges and both exercises'
• The only exception was PV in the lowest velocity range during BP (0.40–0.55 m·s-1), which achieved acceptable CCC
• Poor CCC values indicate that despite reasonable Pearson's r, Velocity Matters did not sufficiently agree with GymAware as a reference standard

Velocity Matters showed sufficient accuracy only for monitoring mean velocity during back squat at velocities below 0.87 m·s-1, but not for bench press at any load.

• Acceptable use of Velocity Matters was limited to 'MV during SQ at velocities <0.87 m·s-1' based on combined validity metrics
• Velocity Matters 'does not provide sufficient accuracy for use in BP across any load'
• The study used GymAware (version 5.1.0) as the reference standard and assessed five velocity ranges in each exercise