Inclusion Criteria:
Peripheral artery disease (PAD) participants:
* Able to provide written informed consent
* 50-75 years of age
* Diagnosed as Fontaine stage II-III
* History of exercise-induced claudication
* Females must be postmenopausal (cessation of menses for \> 24 months)
* Normal renal function (serum creatinine-estimated glomerular filtration rate \>= 60 mL/min) or evidence of stable renal function within the last 6 months
* Normal hepatic function (alanine transaminase \< 87.5 U/L, alkaline phosphatase \< 260 U/L, total bilirubin 1.8 mg/dL) or evidence of stable hepatic function within the last 6 months
* Complete blood count:
* Females: red blood cell 4-5 trillion cells/L, hemoglobin 12-15 g/dL, hematocrit 34-45%, white blood cell count 3-10 billion cells/L, platelet count 160-380 billion/L, and normal lymphocyte count \> 700 million lymphocytes/L, or evidence of stable blood counts within the last 6 months
* Males: red blood cell 4-6 trillion cells/L, hemoglobin 13-17 g/dL, hematocrit 38-49%, white blood cell count 3-10 billion cells/L, platelet count 135-320 billion/L, and normal lymphocyte count \> 700 million lymphocytes/L, or evidence of stable blood counts within the last 6 months
Age-matched control participants:
* Able to provide written informed consent
* 50-75 years of age
* No evidence of peripheral occlusive disease (ankle-brachial index \> 0.90)
* Females must be postmenopausal (cessation of menses for \> 24 months)
* Normal renal function (serum creatinine-estimated glomerular filtration rate \>= 60 mL/min), or evidence of stable renal function within the last 6 months
* Normal hepatic function (alanine transaminase \< 87.5 U/L, alkaline phosphatase \< 260 U/L, total bilirubin 1.8 mg/dL ), or evidence of stable hepatic function within the last 6 months
* Complete blood count:
* Females: red blood cell 4-5 trillion cells/L, hemoglobin 12-15 g/dL, hematocrit 34-45%, white blood cell count 3-10 billion cells/L, platelet count 160-380 billion/L, and normal lymphocyte count \> 700 million lymphocytes/L
* Males: red blood cell 4-6 trillion cells/L, hemoglobin 13-17 g/dL, hematocrit 38-49%, white blood cell count 3-10 billion cells/L, platelet count 135-320 billion/L, and normal lymphocyte count \> 700 million lymphocytes/L, or evidence of stable blood counts within the last 6 months
Exclusion Criteria:
Peripheral artery disease (PAD) participants:
* • Pain at rest and/or tissue loss due to PAD (Fontaine stage IV PAD)
* Acute lower extremity ischemic event secondary to thromboembolic disease or acute trauma
* Limited walking capacity from conditions other than PAD
* No physical exam to assess exercise limitations in the past year
* Currently pregnant or nursing
* Blood work and medical history NOT demonstrating:
* Normal renal function (serum creatinine-estimated glomerular filtration rate \>\> 60 mL/min)
* Normal hepatic function (alanine transaminase 0-35 IU/L, alkaline phosphatase 30-120 IU/L, total bilirubin 2-17 micromoles/L),
* Diagnosis of multiple sclerosis or psoriasis
* Diagnosis of gastrointestinal disorders (e.g., moderate IBS, Crohn's disease, etc.
* Concomitant use of dimethyl fumarate
* Hypersensitivity to diroximel fumarate, dimethyl fumarate, or to any of the excipients of VUMERITY
* Ulcers, gangrene, or necrosis of the foot (Fontaine stage IV PAD)
* Complete blood count NOT within ranges:
* Females: red blood cell 4-5 trillion cells/L, hemoglobin 12-15 g/dL, hematocrit 34-45%, white blood cell count 3-10 billion cells/L, platelet count 160-380 billion/L, and normal lymphocyte count 1-4.8 billion lymphocytes/L
* Males: red blood cell 4-6 trillion cells/L, hemoglobin 13-17 g/dL, hematocrit 38-49%, white blood cell count 3-10 billion cells/L, platelet count 135-320 billion/L, and normal lymphocyte count 1-4.8 billion lymphocytes/L
Age-matched control participants:
* Positive diagnosis of PAD
* No physical exam to assess exercise limitations in the past year
* Any exercise limitations as determined at last physical exam
* Limited walking capacity from musculoskeletal injury
* Currently pregnant or nursing
* Renal function not within normal ranges (serum creatinine-estimated glomerular filtration rate \>\> 60 mL/min)
* Hepatic function not within normal ranges (alanine transaminase 0-35 IU/L, alkaline phosphatase 30-120 IU/L, total bilirubin 2-17 micromoles/L)
* Complete blood count NOT within ranges:
* Females: red blood cell 4-5 trillion cells/L, hemoglobin 12-15 g/dL, hematocrit 34-45%, white blood cell count 3-10 billion cells/L, platelet count 160-380 billion/L, and normal lymphocyte count 1-4.8 billion lymphocytes/L
* Males: red blood cell 4-6 trillion cells/L, hemoglobin 13-17 g/dL, hematocrit 38-49%, white blood cell count 3-10 billion cells/L, platelet count 135-320 billion/L, and normal lymphocyte count 1-4.8 billion lymphocytes/L