Author(s): BAXTER, B.A., BAROSS, A.W., RYAN, D.J., KAY, A.D., Institution: UNIVERSITY OF NORTHAMPTON, Country: UNITED KINGDOM, Abstract-ID: 879

INTRODUCTION:
Periods of inactivity are common amongst older adults, accelerating the loss of muscle strength and size. This inactivity is problematic as low adherence is reported to the recommended twice-weekly resistance training guidelines [1]. While eccentric-only resistance training has demonstrated a superior ability to preserve training-induced adaptations compared to traditional training modalities [2], the influence of weekly dosage on this preservation remains unknown. Therefore, following the cessation of once- or twice-weekly (unmatched volume) 12-week eccentric resistance training programmes, this study examined the effects of a 12-week detraining period on muscle function and structure in older adults.
METHODS:
Participants were randomly assigned to a once- (n = 12) or twice-weekly (n = 11) training programme and completed 12 weeks eccentric resistance training at 50% of their maximal eccentric strength. To determine detraining effects, muscular function (eccentric and isometric strength, power, and timed up-and-go [TUG]) and structure (vastus lateralis muscle thickness, fascicle angle, and length) were measured at post-training (week 1), mid-detraining (week 7), and post-detraining (week 13). Two-way mixed model ANOVAs were conducted to identify significant (P < 0.05) differences with effect sizes (d) calculated to determine the magnitude of change.
RESULTS:
No significant interaction effects indicated a similar regression profile between training groups. No significant regression occurred in any metric of muscular function between post-training and post-detraining (eccentric strength [-1%; d = -0.03], isometric strength [-6%; d = -0.39], power [-6%; d = -0.42], and TUG [-3%; d = -0.39]), resulting in 97, 68, 100, and 100% retainment of training-induced improvements of eccentric strength, isometric strength, power, and TUG, respectively. Conversely, muscle thickness (-10%; d = -1.32) and fascicle angle significantly decreased (-1.8°; d = 0.65]) following the detraining period, resulting in 19 and 0% retainment of training-induced improvements of muscle thickness and fascicle angle, respectively.
CONCLUSION:
Whilst muscle thickness and fascicle angle significantly regressed during detraining, the preservation of improvements in lower-limb muscular strength, power, and functional ability, 12 weeks after the cessation of once- or twice-weekly eccentric resistance training, is indicative of a potent functional training stimulus. Importantly, as training frequency had no effect on the sustainment of training-induced adaptations, these findings have important clinical implications for exercise prescription with the use of eccentric resistance training as a once-weekly strategy to counteract the poor adherence to current twice-weekly resistance training guidelines and age-related declinations in neuromuscular function.