Author(s): SPINELLO, G., SAMPIERI, A., GOLDIN, E., MASARIN, A., FRANCHI, M.V., CAMPA, F., CASOLO, A., PAOLI, A., MORO, T., Institution: UNIVERSITY OF PADUA, Country: ITALY, Abstract-ID: 2224

INTRODUCTION:
Aging is an inherent aspect of human life, characterized by a progressive decline in muscle mass and strength1. Older adults typically experience decreased muscle mass, alteration in muscle fiber size and composition, and impaired neuromuscular function compared to younger adults2. Physical exercise, particularly resistance training (RT), plays a primary role in counteracting age-related problems3. Understanding differences in adaptive response to RT between elderly and younger adults is crucial to optimize training outcomes for both populations. Therefore, we aimed to study changes in response to 8 weeks of RT focused on lower limbs between young adults (Y) and elderly (E).
METHODS:
Fourteen young adults (23.7±3.0 years) and seven older adults (71.9±5.7 years) underwent a progressive dynamic RT program (3 times/week) for 8 weeks. Training protocol involved 3 sets of leg press, lunges, and leg extension and 3 upper body exercises (2 sets). Neither group had prior experience with RT. Participants were assessed at the beginning (T0), after 4 (T1) and 8 (T2) weeks. Isometric muscle strength was evaluated during maximal voluntary force (MVC) and submaximal trapezoidal contractions (15, 35, 50, and 70%), with concurrent recording of high-density surface EMG (HDsEMG) from vastus lateralis muscle. Dynamic muscle strength was evaluated with 1RM leg press and leg extension. Body composition and muscle size (CSA) were assessed with DXA and ultrasonography (US), respectively. Moreover, muscle biopsies were obtained at T0 and T2.
RESULTS:
Preliminary results demonstrated a significant increase in strength parameters. Specifically, isometric MVC significantly increased (p<0.001) from T0 to T1 (Y=+8.52%, E: +15.51%) and from T0 to T2 (Y= +20.49%, E= +17.78%) in both groups and from T1 to T2 in Y only (+8.22%). Similar results were observed in 1RM test. US analysis revealed a time x age interaction (p<0.001) for quadriceps CSA: in particular, Y significantly increased muscle size at all time points, whilst E increased only from T0 to T2. Consequently, the ratio between MVC and CSA was unaltered in the Y group but increased from T0 to T2 in the E group.
CONCLUSION:
Our results suggest that an 8-week RT improved muscle strength parameters and CSA in both cohorts. However, it appears that the adaptive mechanism might be different: in the elderly strength gain seems more attributable to neural adaptation rather than morphological changes. This hypothesis could be further confirmed by the analysis of HDsEMG and muscle biopsies.

1= Lexell J, 1993
2=Mc Leod, 2016
3=Fiatarone, 1994