DISCUSSION • Our results suggest that of the loads and exercises tested, peak and mean velocity at estimated 50% 1RM squat were the least reliable exhibiting moderate and small descriptors respectively • An underlying contributor to this may be the longer deceleration phase within the concentric portion of the lift – shown previously 5,6 – perhaps due to the comparatively low relative (and absolute) 1RM squat of the subjects • This leads to the suggestion that in the squat, with higher mean and peak velocities at lower absolute squat loads across subjects, there is a greater relative contribution of the braking phase to the total concentric time. When assessing reliability, this may have an effect on both peak and mean concentric velocity measurements. This is not apparent in the CMJ due to no braking phase occurring in the concentric portion of the lift • It may be suggested then, that caution be taken when utilising loads to accurately assess changes in performance in a power profile, at 50% 1RM squat or indeed loads that record a mean velocity of 0.79m/s or above or a peak velocity of 1.38m/s or above in the squat • Though both showed very large or greater correlations, we highlighted loaded CMJ to be more reliable than unloaded CMJ in both mean and peak velocity. This may be of consideration for S&C coaches when selecting methods of assessment or monitoring • We reported the SWC across a range of velocities in both ballistic and strength exercises. Highlighting these can give a practical representation on whether or not meaningful changes in performance have occurred in either the squat or CMJ. Coaches can be confident that with lower reporting of SWC, interpreting changes in performance can be confidently assessed with changes in peak and/or mean velocities across the spectrum of loads, above the reported SWC • A limitation to this study is that we may not have captured a wide enough range of velocities in the squat. As has already been suggested 4 capturing mean and peak velocities at the higher end of the spectrum with lighter loads can be confounded by error, so assessing performance changes in loads closer to 1RM and the minimal velocity threshold - suggested at a mean velocity of 0.30m/s 6,7 in the squat - may give a more accurate assessment of performance changes. y = 1.0319x - 0.0931 R² = 0.9847 0 0.5 1 1.5 2 2.5 3 3.5 4 0 0.5 1 1.5 2 2.5 3 3.5 4 Day 2 Peak Velocity (m/s) Day 1 Peak Velocity (m/s) a) Figure 1 – a) peak velocity and b) mean velocity reliability of ballistic and strength exercises across a spectrum of loads PRACTICAL APPLICATIONS • S&C coaches should consider not utilising lighter loads (50% or less 1RM) in power profiles to assess changes in performance. Changes at these loads may be due to movement variation rather than improvements, plateaus or declines in strength or power • Using loaded and unloaded CMJ’s seems reliable, though a loaded CMJ – rather than unloaded – exhibits a lower error and %CV, and its use is suggested with stronger athletes when assessing performance changes or indeed neuromuscular fatigue • Ascertaining SWC scores across loads and exercises is important and S&C coaches are encouraged to create their own data sets in both strength and ballistic exercises, to ensure confidence when assessing potential performance changes • S&C coaches may want to consider taking their time in getting athletes stronger and increasing their absolute 1RM strength, whilst teaching them to jump and land with load before looking to implement performance assessments such as loaded jumps or reliable squat profiling INTRODUCTION Assessing an athletes’ performance or profiling their lower body isoinertial strength may form a daily part of a strength coach’s role. For example, a coach may regularly “track” an athlete’s velocity at incrementally increased loads in a squat – a typical load-velocity profile. Over time, the S&C coach would want to be confident that observed changes in this “profile” are due to real a change in capacity or as a result of expected fatigue. Furthermore, due to the potential variation in day-to-day, and week-to-week lifting velocities expected in an athlete engaged in a strength training program, the S&C coach would want to be sure that shifts in the profile are due to performance change, rather than unreliable assessment methods. The intention of this investigation therefore was to measure the reliability of both peak and mean velocity metrics across a range of loads in two exercises the squat and countermovement jump. METHODS Subjects • 13 male and 4 female state academy of sport hockey players • Age 23 ± 3.8 yr male, 21 ± 2.4 yr female • Mass 80.82 ± 9.48 kg male, 73.44 ± 7.25 kg female • 1RM squat (relative 1.31 ± 0.39; absolute 112 ± 23.96 ) • All 2+ years experience with maximal and ballistic strength training Testing • Subjects performed ballistic (countermovement jump (CMJ)) and strength (squat) exercises across a range of loads (table 1) across two testing sessions separated by seven days • Peak and mean velocity were measured with a previously validated 1 combined portable force plate and linear position transducer (LPT) system capturing variables at 600 (force plate) and 200Hz (LPT) respectively. The repetition with the best peak velocity was used for analysis from each CMJ and squat trial. Statistical Analysis • Test-retest (inter) absolute reliability was measured by the typical error of measurement (TEM). This was expressed in relative terms through the coefficient of variation (CV). Relative reliability was assessed by the intra-class correlation coefficients and confidence interval (ICC, 90%CI). • The magnitude of correlation was assessed with the following thresholds: <0.10, trivial; from 0.10 to 0.29, small; from 0.30 to 0.49, moderate; from 0.50 to 0.69, large; from 0.70 to 0.89, very large; and from 0.90 to 1.00, almost perfect 2 • Smallest worthwhile change (SWC) was calculated as 0.2 x the between-subject standard deviation of the tests, based on the concepts of Cohen’s Effect Size 3,4 RESULTS • Results are shown in table 2. Figure 1 illustrates the regression analysis of both ballistic and strength exercises • Mean velocity showed almost perfect correlation in the 35%CMJ and very large correlation in the BWCMJ, 65% 75% and 85% 1RM squat • Peak velocity showed almost perfect correlation in the 35%CMJ and 85% 1RM squat, and very large correlation in the BWCMJ, 65% and 75% 1RM squat • Both mean and peak velocity at 50% estimated 1RM were small and moderate respectively Queensland Academy of Sport SMARTER, STRONGER, FAIRER REFERENCES 1. Sheppard JM, Cormack SJ, Taylor K-L, McGuigan MR, Newton RU. Assessing the force-velocity characteristics of the leg extensors in well trained athletes: The incremental load power profile. Journal of Strength and Conditioning Research. 2008;22(4):1320-1326. 2. Batterham AM, Hopkins WG. Making meaningful inferences about magnitudes. Sportscience. 2005;9:6-13. 3. Pyne DB. Interpreting the results of fitness testing. Paper presented at: International Science and Football Symposium 2003; Victorian Institute of Sport, Melbourne, Australia. 4. Sullivan GM, Feinn R. Using effect size: or why the p value is not enough. Journal of Graduate Medical Education. 2012;4(3):279-282. 5. Sanchez-Medina L, Perez CE, Gonzalez-Badillo JJ. Importance of the propulsive phase in strength assessment. International Journal of Sports Medicine. 2010;31(2):123-129. 6. González-Badillo JJ, Sánchez-Medina L. Movement velocity as a measure of loading intensity in resistance training. International Journal of Sports Medicine. 2010;31:347-352. 7. Izquierdo, M, Gonzelaz-Badillo, JJ, Häkkinen, K, Ibañez, J, Kraemer, WJ, Altadill, A, Eslava, J, Gorostiaga, EM. Effect of loading on unintentional lifting velocity declines during single sets of repetitions to failure during upper and lower extremity muscle actions. International Journal of Sports Medicine. 2006;27:718-724. Squat or Jump? Heavy or Light? Velocity Measurements are More Reliable at What Loads? Tim Mosey 1 , Will Brown 1 , David G. Watts 1,2 , Georgia Giblin 1 ¹Queensland Academy of Sport, Brisbane, Queensland, Australia, ²Deakin University, School of Exercise and Nutrition Science, Victoria, Australia Email: Tim.Mosey@npsr.qld.gov.au Table 1 – Repetitions and loads used for each ballistic and strength assessment Exercise Additional Load Reps Performed Per Trial BWCMJ 0 3 35%CMJ 35% of BW 3 Squat (back) 50% of 1RM 10 65% of 1RM 5 75% of 1RM 3 85% of 1RM 1 Table 2 - Strength and ballistic exercise reliability data Variable Typical Error % Change in Mean % CV (90% CI) ICC (90% CI) SWC (m/s) Peak Velocity BWCMJ 0.38 -0.5 4.1 (3.1 - 6.2) 0.89 (0.74 – 0.96) 0.063 Peak Velocity 35%CMJ 0.19 -0.6 2.1 (1.5 – 3.1) 0.97 (0.93 – 0.99) 0.049 Peak Velocity 10x 50% 1.01 -3.4 4.7 (3.4 – 8.2) 0.56 (0.01 – 0.85) 0.018 Peak Velocity 5x 65% 0.53 -4.6 4.6 (3.3 – 8.0) 0.83 (0.52 – 0.95) 0.023 Peak Velocity 3x 75% 0.44 -4.5 4.8 (3.5 – 8.4) 0.88 (0.64 – 0.96) 0.028 Peak Velocity 1x 85% 0.31 -7.1 4.6 (3.3 – 8.0) 0.94 (0.81 – 0.98) 0.034 Mean Velocity BWCMJ 0.53 -0.6 5.4 (4.1 – 8.3) 0.81 (0.59 – 0.94) 0.043 Mean Velocity 35% CMJ 0.27 -1.2 2.7 (2.1 – 4.2) 0.95 (0.86 – 0.98) 0.030 Mean Velocity 10x 50% 1.23 -10.4 6.6 (4.7 – 11.6) 0.45 (-0.13 – 0.80) 0.016 Mean Velocity 5x 65% 0.71 -2.6 6.9 (4.8 – 12.7) 0.74 (0.28 – 0.92) 0.018 Mean Velocity 3x 75% 0.58 -3.6 6.3 (4.5 – 11.0) 0.80 (0.45 – 0.94) 0.017 Mean Velocity 1x 85% 0.48 -8.5 8.2 (5.8 – 14.4) 0.86 (0.59 – 0.96) 0.023 y = 1.0298x - 0.0631 R² = 0.9772 0 0.5 1 1.5 2 2.5 0 0.5 1 1.5 2 2.5 Day 2 Mean Velocity (m/s) Day 1 Mean Velocity (m/s) b) 0.45 ICC; 6.6 %CV (50% 1RM squat) 0.56 ICC; 4.7 %CV (50%1RM squat)