The use of commercially accessible activity monitors has increased over the past few years. Assessing the accuracy of these devices is necessary to inform recreational consumers about the validity of these products. PURPOSE: To assess the validity of four activity monitors (Monitor 1, Monitor 2, Monitor 3, and Monitor 4) for energy expenditure (EE) data. METHODS: Twenty-one subjects (8 male and 13 female), with an average age of 20.2 years performed three exercise protocols: walking at 3.0 mph, running at 6.0 mph, and a HIIT workout for ten minutes each. Each exercise bout was followed by a seated rest period until subjects returned to pre-exercise VO₂ values. EE measured in kcal was collected from the Parvo metabolic cart and compared with the EE from four activity monitors. EE from activity monitors was recorded from apps in kilocalories (kcals) upon completion of the testing. Descriptive statistics were performed for all variables. Coefficient of determination (R²) was used to assess the validity of EE in kcals for all devices. RESULTS: Monitor 3 was the most accurate device with an R² of 0.68 for walking, 0.62 for HIIT and 0.59 for running. Monitor 1 showed the weakest correlations for the running (0.27), and the HIIT (0.34) protocols but was comparable to Monitor 3 for walking (0.64). Monitor 2 was the least accurate for walking (R² =0.246) and showed low validity for running and HIIT (0.36 and 0.47 respectively). Monitor 4 was most accurate for higher intensity activities such as running (0.68) and HIIT (0.67). CONCLUSION: Monitor 3 was consistently the most accurate out of tested devices. However, results of this study demonstrate inaccurate assessment of EE by all wearable devices. None of the activity monitors met the correlational standard of 0.7. Future research should continue to assess the validity of these devices to provide accurate information on various modalities and exercise intensities to recreational consumers.