(13) THE EFFECT OF AN 8-WEEK HIGH- VS. LOW-VELOCITY RESISTANCE TRAINING PROGRAM ON MAXIMAL FORCE AND RATE OF FORCE DEVELOPMENT IN OLDER ADULTS

Purpose: The purpose of this study was to examine the effect of an 8-week high- vs. low-velocity lower body resistance training (RT) program on maximal force and rate of force development (RFD) in older adults (OA).

Methods: Eighteen OA volunteered to complete an 8-week RT program (2 x per week) and were randomly assigned to a high- (HV; n=9; age=70±6 y) or a low-velocity RT group (LV; n=9; age=74±7 y). Movement speed for each training repetition was assessed using a linear position transducer during 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 encouraged to move the load as quickly as possible. Isometric maximal force and RFD production were assessed before (PRE) and after (POST) 8-weeks of RT. Peak force (PF) was defined as the highest 500 ms epoc of force (N) achieved during maximal voluntary isometric contraction (MVIC). Peak RFD (pRFD; N•s^-1) was assessed as the highest positive peak of the first derivative of the force-time curve collected during the rapid MVIC (rMVIC). Further, early phase RFD was defined as the highest slope during the first 50ms (RFD₅₀) and late phase RFD was defined as the steepest slope during the 100-200ms (RFD_100-200) of the force-time curve of the best of two rMVIC. All data was calculated offline using custom-written software. Separate 2(condition)×2(time) repeated measures ANOVAs were run to identify differences between groups for PF, pRFD, RFD₅₀, and RFD_100-200. An independent t-test was used to examine the difference in exercise volume (repetitions/load) between HV vs. LV and Hedges’ g was used to estimate effect size. 

Results: There were no significant (p ≥ 0.05) interactions or main effects for time for PF, pRFD , RFD₅₀ , and RFD_100-200. Small effect sizes were observed for PF from PRE-POST in both HV (PRE: 375.46±56.93N vs. POST: 377.9±59.0N, g=-0.1) and LV (PRE 326.5±97.2N vs. POST 317.2±81.7N, g=0.2). Large effect sizes were observed for pRFD in both HV and LV from PRE – POST (HV: PRE = 2230.0±727.0N•s^-1 vs. POST = 2560.4±642.2N•s^-1, g=-1.0; LV: PRE = 1808.3±660.3N•s^-1 vs. POST = 1424.2±458.2N•s^-1, g=-1.4). Small to large effect sizes were observed in RFD₅₀ from PRE-POST in HV (PRE 1312.2±902.5N•s^-1 vs. POST 1194.4±600.2N•s^-1, g=0.3), and LV (PRE 782.8±542.8N•s^-1 vs. POST 561.3±501.5N•s^-1, g=0.9). Small effect sizes were observed in RFD_100-200 from PRE-POST in HV (PRE 1888.3±687.4N•s^-1 vs. POST 1813.2±452.4N•s^-1, g=-0.3) and LV (PRE 1009.5±392.1N•s^-1 vs. POST 955.8±369.27, g=0.3). There were no significant differences in average total volume between groups (p=0.3, g=0.6).

Conclusions: When volume matched, explosive force  production (i.e., pRFD) was increased in the HV and reduced in the LV from PRE-POST suggesting HV improved or maintained explosive force production compared to the LV. Both the HV and LV groups had little change and small effect size in PF suggesting both groups-maintained maximal isometric strength from PRE-POST. Therefore, these data then suggest that movement velocity may be influential in explosive force production adaptations following RT. PRACTICAL APPLICATIONS: These data provide practitioners and strength and conditioning professionals with additional data to design training prescription for their older adult clients.

Acknowledgements: This study was funded by the NSCA through the young investigator grant.