Cortical and spinal responses to short-term strength training and detraining in young and older adults in rectus femoris muscle

Gonzalo Gomez-Guerrero; Janne Avela; Ilkka Jussila; Esa Pihlajamäki; Fu-Yu Deng; Dawson J Kidgell; Juha P Ahtiainen; Simon Walker

doi:10.1007/s00421-024-05443-0

Cortical and spinal responses to short-term strength training and detraining in young and older adults in rectus femoris muscle

Eur J Appl Physiol. 2024 Mar 5. doi: 10.1007/s00421-024-05443-0. Online ahead of print.

Authors

Gonzalo Gomez-Guerrero¹, Janne Avela², Ilkka Jussila², Esa Pihlajamäki², Fu-Yu Deng², Dawson J Kidgell³, Juha P Ahtiainen², Simon Walker²

Affiliations

¹ Faculty of Sport and Health Sciences, NeuroMuscular Research Center, Viveca, VIV221, University of Jyväskylä, 40700, Jyväskylä, Finland. gogomezg@jyu.fi.
² Faculty of Sport and Health Sciences, NeuroMuscular Research Center, Viveca, VIV221, University of Jyväskylä, 40700, Jyväskylä, Finland.
³ Monash Exercise Neuroplasticity Research Unit, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, Australia.

PMID: 38441691
DOI: 10.1007/s00421-024-05443-0

Abstract

Introduction: Strength training mitigates the age-related decline in strength and muscle activation but limited evidence exists on specific motor pathway adaptations.

Methods: Eleven young (22-34 years) and ten older (66-80 years) adults underwent five testing sessions where lumbar-evoked potentials (LEPs) and motor-evoked potentials (MEPs) were measured during 20 and 60% of maximum voluntary contraction (MVC). Ten stimulations, randomly delivered, targeted 25% of maximum compound action potential for LEPs and 120, 140, and 160% of active motor threshold (aMT) for MEPs. The 7-week whole-body resistance training intervention included five exercises, e.g., knee extension (5 sets) and leg press (3 sets), performed twice weekly and was followed by 4 weeks of detraining.

Results: Young had higher MVC (~ 63 N·m, p = 0.006), 1-RM (~ 50 kg, p = 0.002), and lower aMT (~ 9%, p = 0.030) than older adults at baseline. Young increased 1-RM (+ 18 kg, p < 0.001), skeletal muscle mass (SMM) (+ 0.9 kg, p = 0.009), and LEP amplitude (+ 0.174, p < 0.001) during 20% MVC. Older adults increased MVC (+ 13 N·m, p = 0.014), however, they experienced decreased LEP amplitude (- 0.241, p < 0.001) during 20% MVC and MEP amplitude reductions at 120% (- 0.157, p = 0.034), 140% (- 0.196, p = 0.026), and 160% (- 0.210, p = 0.006) aMT during 60% MVC trials. After detraining, young and older adults decreased 1-RM, while young adults decreased SMM.

Conclusion: Higher aMT and MEP amplitude in older adults were concomitant with lower baseline strength. Training increased strength in both groups, but divergent modifications in cortico-spinal activity occurred. Results suggest that the primary locus of adaptation occurs at the spinal level.

Keywords: Aging, resistance training; Cortico-spinal excitability; Lower-limbs; Lumbar stimulation; TMS.