* Aim: to analyse the effects of microcurrent treatment alone, and combined with a resistance exercise programme, on muscle strength, body composition and physical functional capacity in middle-aged adults. * Methods * Randomised, balanced, double-blind parallel-group between-participants design. * Participants - non-regularly trained adults (people who do not engage regularly in physical sessions), aged 40 to 65 years old. * All participants will be invited to take part in a 6-week supervised resistance training programme that will be combined with microcurrent (MC) or sham (SH) intervention. The participants who do not accept to undergo the resistance training programme will integrate a non-exercise group involving a 6-week intervention period using the microcurrent (MC) or the sham (SH) device. The devices will be provided by Arc4Health (ARC Microtech Ltd, UK; https://arcmicrotech.com/arc4health/). The device Arc4Health has regulatory approval as a Class IIa medical device in the areas of pain management and tissue repair. The following will be analysed: 1. Microcurrent alone (MC) 2. Microcurrent with exercise (MC + RT) 3. Sham alone (SH) 4. Sham with exercise (SH + RT) * The participants who agree to take part in the training programme will have 2 sessions a week for a period of 6 weeks. The training programme involves elastic bands and is designed to increase strength and muscle mass. * Measurements of body composition (via plethysmography BodPod), strength, functional capacity, muscular structure (via non-invasive ultrasound), and immunological blood markers will be undertaken at baseline and after the 6-week intervention period.