This is an investigator initiated observational study, designed to study the effect of exercise on transthyretin stability in three main populations: Group 1: healthy master athletes who are 60 years or older. Group 2: Genotype positive (G+) cardiac phenotype negative (P-) patients with variant ATTR (i.e. carriers without evidence of disease). Group 3: Patients with ATTR CA who have not been on a stabilizer (tafamidis) within the last 14 days prior to enrollment.
The goal of this study to investigate if exercise predisposes to transthyretin instability. The investigators will evaluate the effect of exercise on transthyretin biochemistry.