Validity of various portable devices to measure sit-to-stand velocity and power in older adults.

BACKGROUND: Movement velocity and power in a single STS are related to functional performance in older adults. Identifying accessible tools that provide valid measures of STS velocity/power would allow practitioners to evaluate physical function in clinical settings where time, space and finances are limited. RESEARCH QUESTION: Does a linear position transducer (LPT), iPhone application (App), and inertial measurement unit (IMU) obtain valid measurements of velocity and power during a single STS compared with 3D motion capture? METHODS: Twenty-seven community-dwelling older adults aged ≥60 years completed a single STS test with mean velocity and power simultaneously measured with 3D motion capture, an LPT, IMU and App. Acceptable validity was established if the Pearson correlation coefficient (r) was very high (≥0.7) and bias as a standardised effect size (ES) was small (<0.6). The relationship between STS velocity/power and 30s chair STS performance was also evaluated. RESULTS: Measures of STS velocity obtained by the LPT (r = 0.94, ES = -0.21) and App (r = 0.89, ES = -0.19) were very highly valid when compared to 3D motion capture, and were very strongly related to 30s STS performance (r ≥0.74). The LPT (r = 0.87, ES = 0.13) and App (r = 0.74, ES = -0.12) also showed very high correlations and negligible bias for measuring STS power. Data collected by the IMU failed to meet our pre-determined threshold of acceptable validity for STS velocity (r = 0.72, ES = 1.00) or power (r = 0.61, ES = 0.34). SIGNIFICANCE: The LPT and iPhone App, but not the IMU, are valid tools for measuring STS velocity and power in community-dwelling older adults. Clinicians can use STS velocity obtained by either the LPT or App as a simple and valid proxy for functional status, which could help identify patients at high-risk of incident disability.

Test-Retest Reliability of a Commercial Linear Position Transducer (GymAware PowerTool) to Measure Velocity and Power in the Back Squat and Bench Press.

Orange, ST, Metcalfe, JW, Marshall, P, Vince, RV, Madden, LA, and Liefeith, A. Test-retest reliability of a commercial linear position transducer (GymAware PowerTool) to measure velocity and power in the back squat and bench press. J Strength Cond Res 34(3): 728-737, 2020-This study examined the test-retest reliability of the GymAware PowerTool (GYM) to measure velocity and power in the free-weight back squat and bench press. Twenty-nine academy rugby league players (age: 17.6 ± 1.0 years; body mass: 87.3 ± 20.8 kg) completed 2 test-retest sessions for the back squat followed by 2 test-retest sessions for the bench press. GYM measured mean velocity (MV), peak velocity (PV), mean power (MP), and peak power at 20, 40, 60, 80, and 90% of 1 repetition maximum (1RM). GYM showed good reliability (intraclass correlation coefficient [ICC] and standard error of measurement percentage, respectively) for the measurement of MV at loads of 40 (0.77, 3.9%), 60 (0.83, 4.8%), 80 (0.83, 5.8%), and 90% (0.79, 7.9%) of 1RM in the back squat. In the bench press, good reliability was evident for PV at 40 (0.82, 3.9%), 60 (0.81, 5.1%), and 80% (0.77, 8.4%) of 1RM, and for MV at 80 (0.78, 7.9%) and 90% (0.87, 9.9%) of 1RM. The measurement of MP showed good to excellent levels of reliability across all relative loads (ICC ≥0.75). In conclusion, GYM provides practitioners with reliable kinematic information in the back squat and bench press, at least with loads of 40-90% of 1RM. This suggests that strength and conditioning coaches can use the velocity data to regulate training load according to daily readiness and target specific components of the force-velocity curve. However, caution should be taken when measuring movement velocity at loads <40% of 1RM.

Effects of In-Season Velocity- Versus Percentage-Based Training in Academy Rugby League Players.

PURPOSE: To compare the effects of velocity-based training (VBT) vs percentage-based training (PBT) on strength, speed, and jump performance in academy rugby league players during a 7-wk in-season mesocycle. METHODS: A total of 27 rugby league players competing in the Super League U19s Championship were randomized to VBT (n = 12) or PBT (n = 15). Both groups completed a 7-wk resistance-training intervention (2×/wk) that involved the back squat. The PBT group used a fixed load based on a percentage of 1-repetition maximum (1-RM), whereas the VBT group used a modifiable load based on individualized velocity thresholds. Biomechanical and perceptual data were collected during each training session. Back-squat 1-RM, countermovement jump, reactive strength index, sprint times, and back-squat velocity at 40-90% 1-RM were assessed pretraining and posttraining. RESULTS: The PBT group showed likely to most likely improvements in 1-RM strength and reactive strength index, whereas the VBT group showed likely to very likely improvements in 1-RM strength, countermovement jump height, and back-squat velocity at 40% and 60% 1-RM. Sessional velocity and power were most likely greater during VBT compared with PBT (standardized mean differences = 1.8-2.4), while time under tension and perceptual training stress were likely lower (standardized mean differences = 0.49-0.66). The improvement in back-squat velocity at 60% 1-RM was likely greater following VBT compared with PBT (standardized mean difference = 0.50). CONCLUSION: VBT can be implemented during the competitive season, instead of traditional PBT, to improve training stimuli, decrease training stress, and promote velocity-specific adaptations.

Validity and Reliability of a Wearable Inertial Sensor to Measure Velocity and Power in the Back Squat and Bench Press.

Orange, ST, Metcalfe, JW, Liefeith, A, Marshall, P, Madden, LA, Fewster, CR, and Vince, RV. Validity and reliability of a wearable inertial sensor to measure velocity and power in the back squat and bench press. J Strength Cond Res 33(9): 2398-2408, 2019-This study examined the validity and reliability of a wearable inertial sensor to measure velocity and power in the free-weight back squat and bench press. Twenty-nine youth rugby league players (18 ± 1 years) completed 2 test-retest sessions for the back squat followed by 2 test-retest sessions for the bench press. Repetitions were performed at 20, 40, 60, 80, and 90% of 1 repetition maximum (1RM) with mean velocity, peak velocity, mean power (MP), and peak power (PP) simultaneously measured using an inertial sensor (PUSH) and a linear position transducer (GymAware PowerTool). The PUSH demonstrated good validity (Pearson's product-moment correlation coefficient [r]) and reliability (intraclass correlation coefficient [ICC]) only for measurements of MP (r = 0.91; ICC = 0.83) and PP (r = 0.90; ICC = 0.80) at 20% of 1RM in the back squat. However, it may be more appropriate for athletes to jump off the ground with this load to optimize power output. Further research should therefore evaluate the usability of inertial sensors in the jump squat exercise. In the bench press, good validity and reliability were evident only for the measurement of MP at 40% of 1RM (r = 0.89; ICC = 0.83). The PUSH was unable to provide a valid and reliable estimate of any other criterion variable in either exercise. Practitioners must be cognizant of the measurement error when using inertial sensor technology to quantify velocity and power during resistance training, particularly with loads other than 20% of 1RM in the back squat and 40% of 1RM in the bench press.

Back to the Future - in support of a renewed emphasis on generic agility training within sports-specific developmental pathways.

Perhaps as a consequence of increased specialism in training and support, the focus on engendering and maintaining agility as a generic quality has diminished within many contemporary sports performance programmes. Reflecting this, we outline a rationale suggesting that such a decreased focus represents an oversight which may be detrimental to maximising the potential of performers. We present an evidence-based argument that both generic and specific elements of agility performance should be consistently emphasised within long-term performance-training programmes. We contend that prematurely early specialisation in athlete development models can diminish focus on generic movement skill development with a subsequent detriment in adult performance. Especially when this is coupled with poor primary physical education and limited movement experiences. More speculatively, we propose that generic agility can play a role in operationalising movement development through facilitating skill transfer: thereby enabling the learning of new skills, reduce incidence of injury and facilitating re-learning of old skills during rehabilitation and Return-to-Play processes.