(4) THE EFFECT OF HIGH- VS LOW-VELOCITY RESISTANCE TRAINING ON QUADRICEPS FEMORIS CROSS-SECTIONAL AREA & ECHO INTENSITY IN OLDER ADULTS

Purpose: The purpose of this study was to examine the effect of a high- vs. low-velocity lower body resistance training (RT) program on m. vastus lateralis (VL) and m. rectus femoris (RF) cross-sectional area (CSA) and echo intensity (EI) in older adults (OA).

Methods: Nineteen OA volunteered to complete an 8-week RT program (2 x per week) and were randomly assigned to a high- (HV; n=10; age=70±6 y) or a low-velocity RT group (LV; n=9; age=74±7 y). Movement speed for each training and testing repetition was assessed using a linear position transducer during the concentric phase of the belt squat movement. Subjects in the HV and LV were required to move at a mean velocity above 0.7m/s and between 0.25-0.3 m/s, respectively. Load was adjusted to ensure movement speed was within appropriate ranges and participants were provided velocity biofeedback of their concentric movement speed and encouraged to move the load as quickly as possible. One investigator recorded three panoramic ultrasound (US) images of the RF and VL on the right thigh of each participant at baseline (PRE) and after the 8-week RT program (POST). The CSA (cm²) of each muscle (RF_CSA and VL_CSA) was derived from outlining the muscle, excluding as much subcutaneous fat and fascia as possible from the US images. The average of the three CSA calculations were recorded. The EI of the RF (RF_EI) and VL (VL_EI) was determined from the same panoramic US images using gray scale ultrasonography on a scale of 0-255 (au). The EI value was then corrected for subcutaneous tissue thickness using the pre-established equation: Corrected EI = raw EI + (subcutaneous fat thickness (cm) × 40.5278). The average of the three corrected EI calculations were recorded. Separate 2 (condition) × 2 (time) repeated measures ANOVAs were used to identify significant (p≤0.05) differences between groups  for RF_CSA, RF_EI, VL_CSA, and VL_EI. An independent t-test was used to examine the difference between average total exercise volume (repetitions/load) between groups and Hedges’ g was used to estimate effect size.

Results: There were no significant interactions for RF_CSA, RF_EI, VL_CSA, or VL_EI. However, there was a significant main effect for time for VL_CSA (PRE: 12.53 ± 3.93 cm² vs. POST: 14.64 ± 3.87 cm², p=0.03, g = -1.07). Medium to large effect sizes were observed in the HV group for  RF_CSA (PRE: 8.02 ± 1.73cm² vs POST: 8.36 ± 1.50 cm², g = -0.42), VL_CSA (PRE: 12.87 ± 3.43cm² vs POST: 14.64 ± 4.22 cm², g = -0.94), and VL_EI (PRE: 89.80 ± 30.12 au vs POST: 80.85 ± 18.51 au, g = 0.73). Medium to large effect sizes were also observed in the LV group for RF_CSA (PRE: 7.64 ± 2.36 cm² vs POST: 8.31 ± 2.11 cm², g = -0.62) and VL_CSA (PRE: 12.14 ± 4.60 cm² vs POST: 14.63 ± 4.00 cm², g = -1.20). There was no significant difference in the average total exercise volume between groups over the 8-week training period (HV = 47,490± 10,888 kg vs LV = 45,705± 16171kg, p = 0.81, g = 0.27).

Conclusion: These data suggest that when total exercise volume is matched, both HV and LV RT programs improve RF_CSA and VL_CSA in OA_. The significant increase in VL_CSA observed for groups collapsed across time and the reduction in VL_EI suggest that the increase in VL_CSA  was due to an increase in muscle tissue. Practical Applications: Clinicians, coaches, and practitioners can incorporate both HV and LV training techniques in exercise programing for older adults to increase lower body CSA and muscle quality.


Acknowledgements: Funded by the Young Investigator Grant from the NSCA