Phase 1. Pre-measures: Pre-measures will occur over the course of 2 days.
Visit 1:
MRI scan: Participants will report to the MRI facility and fill out an MRI safety
screening form. Upon completion, a 3-Tesla magnet will be used to image their left thigh
(for more detail on MRI protocol see section 7.4 below).
Visit 2:
Blood flow and vascular function measurement: Upon arrival, participants will rest on a
chair for 15 minutes with their left leg resting on a rolling desktop to stabilize their
heart rate and blood flow. Blood flow will be measured with Doppler Ultrasound at the
Common Femoral Artery while the subjects rest and while their leg is passively moved
through a 90° range of motion. This test will be repeated 3 times to determine the
dilatory function of the resistance arteries of the leg.
Muscle biopsy: After completing the vascular function measurement, subjects will lie down
on a treatment table. Their left thigh will be prepped, cleaned, numbed with lidocaine,
and biopsied.
Muscle strength and endurance measurement: Subjects will be seated in a chair with their
leg bent to 90° (hanging straight down) and ankle fastened in a custom brace that is
attached to a strain gauge. Subjects will be asked to kick against the immovable brace
multiple times at moderate intensities. They will then be asked to kick as hard as they
can to determine their maximum voluntary contraction (MVC). Then they will kick at 40-45%
of their MVC until the generated force drops below 40% of MVC.
Providing a knee brace and crutches: In this study, the subjects' left leg will undergo
immobilization using an aluminum frame knee brace. Trained lab personnel will instruct
the subjects on how to properly apply and remove the knee brace. Crutches will be
provided so that they can get around while staying off the assigned leg. The subjects
will be instructed on how to properly use the crutches. We will confirm their ability to
use the crutches properly and practice going up and downstairs in order to increase their
familiarity with the demands of using crutches. They will also need to fill out an
activity assessment questionnaire during each lab visit and at home during the next 7
days of recovery after the biopsy.
Phase 2. Immobilization
The subjects are asked to apply the knee brace and start using crutches from the morning
of the day they come for their 3rd visit. The immobilization period will last 10 days.
The brace should be worn at all times throughout the day, but can be taken off at night
during sleep. During each visit to the lab, the subjects will fill out the food log and
activity assessment questionnaire.
Visit 3: Subjects will lie down on a treatment table, with their knee brace removed for
15 minutes to stabilize their heart rate and blood flow. Then their baseline blood flow
will be measured with a doppler ultrasound at the common femoral artery. The subjects in
the massage group will receive percussive massage on their thigh for 30 minutes and the
subjects in the control group will lie down on the bed without receiving any treatment
(the subjects are randomized into massage or control groups after they enroll in the
study). Every 5 minutes, the percussive massage stops, and blood flow will be measured.
There will be a total of 7 blood flow measurements (each for 30 seconds) during this
visit.
Visit 4-20: The subjects will report to the lab twice a day to receive percussive massage
(massage group) or lie on the bed (control group) for 30 minutes. In order to monitor the
level of pressure the subjects received during the percussive massage, a pressure
perception chart will be used. Based on the subject's feedback throughout the training
session, the investigators will be able to keep the pressure at a moderate level
Visit 21: same as visit 3
Phase 3. Post-measures: Post-measures will occur in 1 day.
Visit 22: 24 hours after their 21st visit, the subjects will return the knee brace and
crutches. Then they will undergo an MRI scan, vascular function measurement, biopsy, and
muscle strength and endurance tests. All tests will be the same as pre-measures.