Metabolic Equivalents of Safe Physical Activity Levels at Anaerobic Threshold in Anorexia Nervosa Patients
Abstract Purpose Patients with anorexia nervosa (AN) require appropriate nutrient therapy and physical activity management. Eating disorder treatment guidelines do not include safe, evidence-based intensity criteria for exercise. This study used cardiopulmonary exercise testing (CPX) to evaluate the exercise tolerance of patients with AN and develop treatment guidelines to optimize their physical activity. Methods CPX was done with 14 female AN patients admitted to a specialized eating disorder unit between 2015 and 2019. Their anaerobic threshold (AT) was determined by assessing their exercise tolerance using CPX and compared with 14 healthy controls (HC). The metabolic equivalents (AT-METS) were compared when AT was reached. We examined factors related to AT (AN-AT) in the AN group, including age, body mass index (BMI), previous lowest weight, minimum BMI, past duration of BMI < 15, exercise history, and ΔHR (heart rate at the AT - resting heart rate). Results The AT of the AN group (BMI: 15.7 [Mean] ± 1.8 [SD]) was significantly lower than the HC group (BMI: 19.7 ± 1.8) (AN: 10.0 ± 1.8 vs HC: 15.2 ± 3.0 ml/kg/min, P<0.001). AT-METS was also significantly lower in the AN than the HC group (AN: 2.9 ± 0.52 vs HC: 4.4 ± 0.91, P<0.001). AN-AT was highly influenced by ΔHR. Conclusion The AT-METS level for these AN patients was 2.5-3.3 METS, and this index can be used by clinicians to teach AN patients a safe exercise intensity. CPX and AT-METS are useful tools for clinicians to manage physical activity in AN patients. Level of evidence III: Evidence obtained from case-control analytic studies