Author(s): KELLER, M., LUDYGA, S., LICHTENSTEIN, E., Institution: UNIVERSITY OF BASEL, Country: SWITZERLAND, Abstract-ID: 2081

INTRODUCTION:
Research in younger individuals indicates that resistance training performed to failure can stimulate similar muscle growth across a wide range of loads (Schoenfeld et al., 2017). Thus, low-load (LL) resistance training may offer a joint-friendly alternative while still promoting muscle hypertrophy for older adults. However, studies investigating low-load resistance training in this age group – especially when comparing effect to high-load (HL) resistance training – are scarce. The aim of this study was therefore to compare the effects of eight weeks of LL resistance training to failure compared to HL on muscle strength, neuromuscular activation and executive function in older adults.

METHODS:
In this randomized controlled trial, older adults took part in resistance training at 40% or 60% 1-repetition maximum (RM) to failure, two times per week for 8 weeks. Training included leg extensions, leg curls, and leg press exercises in commercially available machines. Strength gains were assessed using isometric contractions in a dynamometer and 1RM performance estimated from 5-RM tests. We used ultrasonography to quantify muscle thickness in the vastus lateralis and the twitch interpolation technique to assess the level of voluntary activation. Executive function was assessed by computerized Flanker (FL) and Go/No-Go tasks (GNG). Mixed effects models were used accounting for differences in sex, age and BMI. Standardized effect sizes with 95% confidence intervals are reported for time*group interactions.

RESULTS:
Available data include 16 older adults (10 women, 64.7 ± 4.2 years, 24.0 ± 3.3 kg/m2) while data of approx. 32 participants will be analyzed at the time of the presentation. Isometric strength showed slightly higher gains after LL than HL (d = 0.13 (-0.24; 0.51)). Leg curl (-0.30 (−0.67; 0.06)) and extension (−0.53 (−1.15; 0.09)) 1RM strength increased more after LL, while the HL group increased more in leg press 1RM (0.22 (−0.14; 0.59)). The level of voluntary activation increased more after HL when compared to LL (-1.36 (-2.91; 0.20)). In both cognitive tasks, reaction times in trials with low inhibitory control demands showed favorable effect sizes for the LL group (FL: 0.94 (0.06; 1.81); GNG: 0.77 (-1.18; 2.72). Under high demands, results where divergent (FL: 1.44 (0.12; 2.77); GNG: -0.69 (-2.20; 0.83).
CONCLUSION:
The preliminary data analysis revealed negligible group difference for strength. Thus, resistance training to failure in older adults results in potentially relevant strength gains independent of the chosen load. In line with previous evidence, HL has improved the level of voluntary activation more than LL. To the authors surprise, the preliminary data analysis revealed large benefits for the LL group in inhibitory control.
References

Schoenfeld et al (2017) J Strength Cond Res