Smartpaddle as a New Monitoring Feature: A Comparison Between Inertial Measurement Unit- and Strain Gauge-Based Devices on Tethered Swimming Forces.

Smartpaddle is a novel wearable device based on inertial measurement units (IMU) for in-field arm-stroke kinetics and kinematics analysis in swimming. However, the lack of data regarding its agreement and reliability, coupled with restricted access to raw data, emphasizes the need to evaluate it against a well-established strain gauge (SG) reference method for assessing swimming forces. Thus, this study aimed to investigate the agreement and reliability between the Smartpaddle and strain gauge in a 30-s all-out arms-only tethered swimming test. Twelve trained young adult swimmers performed a test-retest 30-s all-out arms-only tethered swimming trial. Peak and mean forces were obtained from IMU (PF and MF) and SG (PF and MF) simultaneously. Statistical differences and correlations were found in both peak (PF = 158.46 ± 48.85 N, PF = 75.47 ± 12.05 N, < 0.001, = 0.88) and mean (MF = 69.62 ± 16.36 N, MF = 30.06 ± 5.42 N, < 0.001, = 0.84) forces between devices, presenting elevated systematic errors for both variables. No differences were found in IMU data between test-retest conditions in both peak (PF = 75.47 ± 12.05 N, PF = 75.45 ± 11.54 N, = 0.99, ICC = 0.96) and mean (MF = 30.06 ± 5.42 N, MF = 30.21 ± 5.83 N, = 0.80, ICC = 0.95) forces, with negligible systematic errors. In conclusion, although the Smartpaddle® device is not directly comparable to the strain gauge reference method, it has demonstrated high reliability levels in test-retest trials.