Understanding the Effects of Pulmonary Arterial Hypertension on Lean Muscle Mass-Substudy (MUSCLE-UPSUB)

After obtaining informed consent, patients will be scheduled for an in-person substudy baseline visit. The subject will have their vital signs checked, will complete the E10 questionnaire, have blood drawn, and will complete exercise testing:

an occlusion device (Kaatsu B2 model) will be applied to the thigh area and a wireless NIRS device (PortaMon, Artinis, The Netherlands) will be applied over their right gastrocnemius muscle and secured with strap. The participant will be seated in a chair and allowed to rest for up to 10 minutes, and then the participant will begin performing seated heel raises. Once comfortable with the maneuver, the occlusion device will be inflated to systolic blood pressure (SBP) + 50 mmHg for 5 minutes and the participant will be asked to resume the seated heel raises. Then the cuff will be deflated at the completion of the 5 minutes. This will be followed by a 10-minute rest period and then repeated (cuff inflation and exercises for another 5 minutes). The occlusion device will then be removed, and the patient will continue wearing the NIRS in the seated position for another 20 minutes to capture the recovery phase.

A post-exercise blood draw will completed during the recovery phase.

A certified exercise physiologist will demonstrate the at-home exercises to the participant and assess their strength level and observe them performing them ensuring proper form and technique. Each exercise will be performed in 3 sets of 15-15-15 repetitions. A handout will be given to the participant to be used as a resource during the 12 +/- 1 week period between visits.

Low-load resistance training exercises:

Seated heel raises: Starting from seated position in a chair, the participant will place both their feet on the floor. Next they will press down with the forefoot and toes to raise their heels up off the floor. Then, they will lower their heels back down and repeat. They will be asked to keep their toes down on the floor the entire time.

Depending on the participant's strength, this exercise will be upgraded to seated heel raises with resistance. Participant will be in seated position on chair and will have a weight placed on their thigh comfortably. Then heel raises will be performed as described above.

The next upgrade to this exercise will be standing double heel raises: Participants will be asked to stand near a wall/counter for balance support as needed. The participant will lift up onto the balls of their feet and then slowly lower their heels back to ground and repeat as needed.

The next upgrade to this exercise will be standing single heel raises: Participants will be asked to stand near a wall/counter for balance support as needed. The participant will lift one leg up, bending at the knee then lift up onto the ball of their foot that's on the ground. The participant will then slowly lower their heel back to the ground and repeat as needed.

Plantar flexion: While sitting on the floor or a mat, the participant will place the band around the ball of their foot and toes and pull back until they feel a gentle stretch. The participant will press down on the band using their ankles but keeping their toes relaxed. Then the participant will press down fully with the toes. To release let the band, the participant will pull the toes up first before releasing the ankle back to start. The band resistance will be upgraded as the participant progresses.

Sit to stand: The participant will start by scooting close to the front of the chair. Next, they will lean forward at their trunk and reach forward with their arms and rise to standing without using their hands to push off from the chair or other object. The participant will use their arms as a counter-balance by reaching forward when in sitting and lowering them as they approach standing.

Depending on patient's progress, this will be upgraded to box squats: with hands out in front of the participant, they will bend forwards at the hips, like they are going to sit back on a chair (get their hips as far away from their ankles as they can) and then return to standing. The participant will not sit; just tap the box with their bum. The participant will use the box or chair below as a target to hit as they squat down.

The next upgrade will be to loaded sit to stands: With the participant sitting on a sturdy chair and holding onto a medicine ball, or a weight, they will keep the weight close to the body. Keeping their back straight, the participant will lean forward at the hips (hip hinge) to get their weight over their feet. Then the participant will stand all the way up tall and make sure to keep their abdominals drawn in during the task.

Once each participant feels comfortable in performing the exercises independently, they will be provided with the resistance bands to go home. Each participant will be instructed to perform these exercises 3 times per week at their discretion and to log their completion in the exercise diary. The participant will then be scheduled for a follow-up visit mirroring the baseline visit at 12-weeks +/- 1 week. At the 12-week visit, the participant will also complete the E10 questionnaire and that will conclude their substudy participation.