The workouts that are performed under normal outdoor conditions are more difficult than those performed in controlled internal environments. This means that the workout output and benefits of running outdoors can never be replicated by running on a treadmill. Research studies that have been conducted throw light on the fact that for the same parameters (speed and gradient) the energy expended on a treadmill is lower than that expended while running outdoors. This may perhaps be due to the inherent running mechanism involved as well as due to increased drag or resistance experienced in outdoor conditions. A study in the late 90’s conducted by scientists in UK stated that a 1% gradient accurately reflected the energy expenditure of running outdoors when speed and distance are same in both cases. Similar results have been seen in other activities such as cycling.