Research Study Participation

• Are a recreationally active female (≥150 minutes per week of moderate to vigorous aerobic activity) between the ages of 18-35.
• Meet the study’s aerobic fitness eligibility requirement (assessed during Visit 1: achieve an age-specific “fair” or greater cardiorespiratory fitness classification (≥34.6 ml∙kg-1∙min-1) during the maximal graded exercise test).
• Are willing to come in for all seven study visits and complete all study activities.

• Are a recreationally active male or female (≥150 minutes per week of moderate to vigorous activity) between the ages of 18-35.
• Are willing to come in for four visits

• At least 3 episodes of self-reported LBP with or without radicular symptoms that limited daily activities in the past 6 months
• A minimum average score 3/10 on the Numeric Pain Rating Scale (calculated by the mean of the least current and most amount of pain present in the past week)
• Be able to lay down on and stand up from the ground independently.
• Ages 18-65
• Be able to read and write in English

• Younger adults aged 18–35 years with a body mass index (BMI) of 18.5–34.9 kg/m² who have participated in lower-body resistance training at least twice per week for the previous 6 months.
• Older adults aged 70 years and older with a body mass index (BMI) of 18.5–34.9 kg/m² who have not participated in lower-body resistance training during the previous 6 months.

• Are a recreationally active (≥150 minutes per week of physical activity) male between the ages of 18-35.
• Are willing to come in for all five visits.

• Adults aged 18 to 35 years
• Had lower extremity musculoskeletal surgery within the previous 6 months.
• An age-matched control group of adults without a history of lower extremity musculoskeletal surgery will also be included.

• are between the ages of 18-35 years,
• either have had an anterior cruciate ligament reconstruction (ACLR) surgery or have not had an injury to either of your knees,
• have not been medically diagnosed with a concussion in the previous 6 months,
• have not been medically diagnosed with colorblindness,
• have no known neurological (nervous system) disorder (i.e. Multiple Sclerosis),
• have not taken opioid medication (pain medication) in the last 2 weeks,
• are not pregnant of planning to become present during study participation, and
• have no contraindications to brain MRI (you will complete a screening form).

ACL Group:

• Age of 18-35 years
• History of only one ACL reconstruction within the previous 2 years
• Medical clearance for return to unrestricted activity

Uninjured Group:

• Age of 18-35 years
• No history of lower limb surgery
• No history of significant lower limb injury within previous 6 months (defined as seeking medical attention, or missing >3 consecutive practices or games)

• Age 12-45 years
• History of knee injury (e.g., ACL tear, meniscus tear, patellofemoral pain, osteoarthritis) or surgery (e.g., ACL reconstruction, meniscectomy or repair, total knee arthroplasty) within the last 2 years