The goal of this clinical trial is to compare the effects of resistance training (RT) preconditioning vs no training on disuse-induced atrophy and post-disuse resistance training in young healthy individuals. The main questions it aims to answer are:

• To determine if performing RT prior to a period of disuse enhances the regain of strength, skeletal muscle size, and skeletal muscle quality while performing RT after a period of disuse.
• To determine if performing RT prior to a period of disuse dampens the maladaptive effects of disuse on muscle size, muscle quality, and strength.
• To determine the anabolic and proteolytic mechanisms underpinning the observed outcomes.

Participants will:

1. Perform either 6 weeks of resistance training or maintain an untrained lifestyle
2. Perform 2 weeks of limb immobilization induced disuse of a randomized leg
3. Perform 6 weeks of resistance training

Researchers will compare the resistance training preconditioning condition vs the non-trained condition to see if resistance training prior to a period of disuse is beneficial during the disuse period and in the return to training period on skeletal muscle size, strength, and underpinning molecular markers.

Inclusion Criteria:

• Between the ages of 18-30
• Free from medical implants in lower extremity that would interfere with low-dose radiation
• Are not allergic to ultrasound gel or Lidocaine
• Have no or minimal experience with resistance training (less than 1 training session/week for a 1 year period)

Exclusion Criteria:

• Have been exposed to medically necessary radiation in the past 12 months other than dental x-rays
• Have known overt cardiovascular or metabolic disease
• Have a medical condition that would contraindicate participating in an exercise program or donating a skeletal muscle biopsy (e.g. blood clotting disorder, taking blood thinners, etc.)
• Are undergoing medical treatment for a disease that would interfere physiologically or logistically with study outcomes and/or protocols (e.g. undergoing chemotherapy and/or radiation for cancer treatment)
• Have consumed supplemental protein, creatine, and/or agents that affect hormone status (e.g. testosterone, growth hormone boosters, etc.) within the previous 2 months.