Consistency and stability of the load-velocity profile before and after a six-week strength and power intervention

Dorrell, Harry, Moore, Joseph and Gee, Thomas (2020) Consistency and stability of the load-velocity profile before and after a six-week strength and power intervention. In: National Strength and Conditioning Association 2020 National Conference.

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Abstract

Purpose: Explore the consistency of the free-weight back squat load-velocity profile (LVP) before and after completion of a six-week strength and power intervention. Method: Nineteen resistance trained males (mean ± SD; age: 23.6 ± 3.7 years; stature: 182.7 ± 5.1 cm; body mass: 92.2 ± 8.7 kg; back squat 1-RM: 150.7 ± 23.7 kg) completed a LVP assessment twice, prior to and following completion of six-weeks of resistance training. During LVP assessment, initial load was set at ~30% estimated 1-RM, with incremental increases of ~5% estimated 1-RM following completion of successful repetitions, until 1-RM was achieved. Mean concentric velocity (MCV) was recorded and plotted against relative percentage 1-RM for each participant before a second-order polynomial line were fit to establish the LVP. Consistency and stability of the LVP were assessed via analysis of MCV at each 10% relative load increment of the LVP (30-100% 1-RM). Consistency was assessed between pre-intervention (trial 2 vs. 1), and post-intervention (trial 4 vs. 3) profiling sessions; stability was assessed by comparing the mean data between the pre- and post-intervention assessments. Analysis of the slope of the least products repression (LPR) line and bootstrapped limits represented proportional bias. Systematic and random bias were assessed by quantifying the 95% limits of agreement (LOA). LOA were interpreted in relation to the difference in velocity representing a 2.5% difference in relative load (e.g. 97.5% - 100.0%). Results: Consistency analysis supported that LVPs have acceptable levels of proportional and systematic bias, shown by the slope of the regression line being close to one and the mean differences being smaller than velocity differences representing 2.5% 1-RM (Table 1), respectively. These findings were also shown in the stability analysis, where despite a significant increase in back squat 1-RM (13%; p >0.01), bias levels were acceptable. Random bias, displayed by the spread of the LOA, were equivalent or slightly larger than a velocity difference representing 2.5% 1-RM for both consistency and stability analyses. Random bias in the stability analysis was smaller than in the consistency data suggesting the long-term error is explained by the day-to-day variability and was not affected by the intervention. Similar random bias in consistency and stability analysis supports that a 6-week intervention did not alter LVPs.
Conclusion: LVPs showed acceptable levels of systematic and proportional bias supporting consistency and stability even in the presence of significant strength increases. Random bias was small and at similar levels at an acute (consistency) and long term (stability) timeframe. PRACTICAL APPLICATION: Sufficient evidence is provided supporting the stability of LVPs over a six-week period. Such findings provide confidence in the use of LVPs, alleviating the concern that as participants become stronger, their associated LVP will change and require retesting.

Keywords:Velocity based training, Load-velocity profile, Strength, Power
Subjects:C Biological Sciences > C600 Sports Science
Divisions:College of Social Science > School of Sport and Exercise Science
ID Code:42202
Deposited On:25 Sep 2020 10:12

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