Exercise Intolerance

OBJECTIVES

After completing this article, the reader should be able to:

1. Explain the causes of exercise intolerance.

2. List the two most useful diagnostic tools for assessing exercise intolerance.

3. Describe how pulmonary dysfunctions, cardiac diseases, and muscular disorders affect exercise tolerance.

4. Delineate the nonpharmacologic treatment of choice for most cases of exercise intolerance.

5. Explain the role of behavioral modification within a family-based intervention for exercise intolerance.

Introduction

Exercise intolerance is a general term associated with individuals whose responses to the challenges of exercise fail to achieve levels considered normal for their age and gender. In the pediatric population, exercise intolerance most frequently is associated with dysfunctions of the pulmonary, cardiovascular, and neuromuscular systems, although psychogenic and behavioral causes also place large numbers of children at risk. The reference standard for determining exercise intolerance is the maximal oxygen consumption (˙Vo₂ max) test. Identifying perturbations in components of the Fick equation (Figure⇓ ) associated with this test is useful for diagnosis, for explaining signs and symptoms, and for evaluating therapeutic interventions. In this brief review we examine some commonly encountered pediatric disorders associated with exercise intolerance.

Pulmonary Disorders

The two most common childhood pulmonary disorders associated with exercise intolerance are exercise-induced asthma (EIA) and cystic fibrosis (CF). Exercise intolerance may be a presenting symptom for other chronic lung dysfunctions, such as interstitial lung disease and alveolar proteinosis, but these are less common and are not discussed here.