• 18-55 years of age

• Pain-free
• 18-60 years old
• Participant can appropriately perform the knee extension exercise (assessed during screening)

• Individual between the ages of 18 to 58
• Diagnosed with Multiple Sclerosis
• Are able to walk 10 meters without assistance
• Are willing to come in for all 4 visits
• No other known cardiovascular, pulmonary, metabolic, muscular, and/or coronary heart disease
• No Multiple Sclerosis relapse in the past 30 days
• Are not currently undergoing a rehabilitation protocol
• Are not currently seeking medical care for a chronic condition that could limit exercise capacity other than multiple sclerosis
• Are not currently pregnant

• Healthy adult aged 18-30, with a body mass index between 18.5-35.0 kg/m2
• Willingness to comply with exercise, caffeine, and alcohol requirements.
• Willingness to perform maximal strength testing and undergo brain stimulation.
• Have no other major underlying health concerns and circumstances as described in the pre-enrollment health screen administered before enrollment.

• Men and women between the ages of 18 to 35
• Are willing to come in for one visit lasting 1hr

Part 1

• Male between the ages of 18-45 years old
• Healthy as determined by the PAR-Q+
• At least recreationally active (3 or more days a week)
• English speaking

Part 2

• Male between the ages of 18-45 years old
• Healthy as determined by the PAR-Q+
• English speaking
• At least recreationally active (3 or more days a week)
• Jiu jitsu practitioners with greater than 2 years of jiu jitsu experience OR holding a blue belt or higher in jiu jitsu

• pain-free
• 18-60 years old
• participant can perform the knee extension exercise (assessed during screening)

• Resistance trained females between the ages of 18-35
• Trained individuals are defined as having resistance trained at least 2x/week for the past 6 months as per ACSM guidelines
• Willing to come in for all testing visits

• Male or female between the ages of 18-55 years old
• Healthy as determined by the PAR-Q+
• English speaking

• Ages 18-45,
• Have a biological sex of male or female
• Have self-reported low back pain within the previous 6 months or greater than 3 episodes within the past 3 years