Re: How can i figure out what will be an aerobic workout for me?
The term aerobic means "with oxygen" and anaerobic means "without oxygen". On a cellular level, they refer to separate pathways of substrate metabolism, ie. in aerobic metabolism (like the Krebs cycle), fat is burned; in anaerobic metabolism (glycolysis), glucose is burned.
An activity can be either aerobic or anaerobic depending on the duration and your level of exertion. For example, a low-intensity jog for 30 minutes would be considered mostly aerobic, a 400 meter sprint would be considered mostly anaerobic, treadmill running for 15 minutes would be considered aerobic but if you were to run vigorously and max out after 1-2 minutes, then that would be anaerobic. Same with lifting a weight to failure under 60 seconds -- anaerobic. A marathon is an example of a combination aerobic and anaerobic event. Generally, aerobic activites are usually sustainable for longer periods of time (eg. 20-60 minute sessions) than anaerobic activities (maximum a few minutes due to exhaustion of PCr, ATP fuels, etc.).
You can use the heart rate reserve method to calculate your target heart range (the formula uses your age and resting heart rate), but keep in mind that these zones are estimates, subject to error, and not appropriate for everyone. 60% to 90% is the usual training range for aerobic fitness. However, some people can sustain workouts at higher workloads with no difficulties, or some people naturally have lower resting heart rates which would result in a lower training zone at any given intensity, etc.
A better option would be to gauge your exercise intensity by your exertion level. On a perceived exertion scale of 1-10 (a variation of Borg's scale), where 1 is extremely light exertion, 5 is somewhat hard, 6 is hard, and 10 being extremely hard, you want to keep the intensity between 5 and 6 in order to gain fitness and health benefits. Your rate of breathing is also a good indicator of whether you're working out aerobically (breathing slightly hard, talk test) or anaerobically (totally out of breath, panting for oxygen).