You head to the gym, hop on an exercise machine for 30 minutes, and at the end your heart is racing and you’re soaked in sweat.  You feel like it was a great workout, but was it? Just watching time, distance and calories doesn’t always give you the straight story.  

The cardiovascular equipment you’ll find at the gym may give feedback on time, distance, heart rate, elevation, speed, pace, calories burned, watts and METs; but choosing how to gauge the quality of your workout can be difficult. Here’s a guide from Life Fitness to keep you on track:

Time:  The machine acts as a stop watch and measures your time (backwards or forwards) working out. The American Heart Association recommends 30 minutes of exercise per day, five days a week for adults under age 65.

Distance: On a treadmill, distance is measured from the revolutions of a belt over time. But on an exercise bike or elliptical cross-trainer the formula can vary. In other words – don’t expect the energy you burn while running on a treadmill to be the same as what you experience with the same distance on a stationary exercise bike. A moderate exerciser should aim to run about 3 to 6 miles on the treadmill or elliptical cross trainer.

Heart Rate: The heart rate monitor measures beats per minute. Exercisers should aim to work at about 50 to 65 percent of their maximum heart rate. Subtract your age from 220 to get a rough estimate of your theoretical maximum heart rate.

Watts: Watts is an expression of the amount of energy you’re spending on the workout, or the amount of power required by the machine to maintain the workout load. Some Life Fitness cardio equipment will let you set a specific watt level to maintain. Set the machine at 100 watts if you are a beginning exerciser, but crank up the intensity to 150 or 200 watts if you’re more experienced.

METs: This is the abbreviation for ‘metabolic equivalent’ and equates to the amount of oxygen your body consumes at rest. This number is then compared to the oxygen you consume when exercising. For example if you are biking at 5 METs, you are consuming 5 times the amount of oxygen than when resting. While METs are typically used in clinical settings to assure consistent levels of exertion for test subjects, moderate exercisers should aim for 3.0 to 5.9 METs.