Exercise mode refers to the specific activities an individual must train in to become better at their desired sport or event. Obviously, if one is to become a better runner, swimmer or cyclist, they would need to practice their desired event as that would be the ideal specificity training.
Having said that, there are numerous research studies that have been done showing the positive effect cross training can have on any athletic event. Cross training should try and involve as many of the desired body parts as possible though. For example, it would not be as effective for an athlete who is training for a cycling event to spend a lot of time on the bench press.
P90X is considered as an overall fitness and conditioning program since it targets so many of the body's energy systems. It is ideal to get individuals in great overall shape, the downside to that however, is that no individual sport or training style gets targeted specifically. This should not be surprising, however, since this is a home workout program catered "to the masses," so if you are wishing to train for a specific sport, then a more sport-specific training regimen should be implemented at some point during your training cycle.
For the most part, the longer a training session is, the less-intense it is and vice-versa. Our muscles consist of a combination of type 1 and type 2 muscle fibers. Type 1 fibers are more fatigue-resistant because their primary energy source is derived from aerobic metabolism, although they cannot create as much power as type 2 fibers can.
Type 2 muscle fibers are more intended for power and speed, although they do so by producing energy by means of anaerobic metabolism. As the intensity of any activity increases (heart rate), the body begins to transition from mostly type 1 fiber recruitment to type 2, although this is never a black and white transition, there is always some time with overlap.
By training both of these muscle fibers and their subsequent energy systems by using aerobic exercise, you are able to increase the fatigue-resistance of the type 2 fibers by training them to be more aerobically efficient. By doing so, you improve your overall aerobic performance.
The trick to aerobic training is to not train too intensely because a training session would be cut too short, but to also not push the envelope too far, so to speak, as you would not be improving the efficiency of your energy systems.
P90X workouts are intended to be the length of time that they are so that you train intensely during that time, primarily working your anaerobic energy system. Having said that, your heart rate generally stays elevated throughout, as your body compensates for the work being done, so you get some "aerobic" training as well.
This is where there is a lot of confusion surrounding P90X workouts. It is common for individuals to feel as though they need to run, jump, cycle, etc. to be working their cardiovascular system (cardio workout). However, the definition of "cardio" simply means to elevate your heart rate above your general resting rate for an extended period of time.
By that definition, every single P90X workout could be considered a "cardio" workout since your heart rate will be elevated throughout. Having said that, to effectively train for an endurance event (i.e. marathon) then one should integrate specific cardiovascular training into their regimen to ensure the body effectively transitions its muscle fibers to be more aerobic in nature. To re-iterate what has been said earlier, P90X will improve your overall fitness, but to train for a specific sport, one would be advised to implement sport-specific training.
To date, there are a few different techniques that an individual can use in order to monitor their level of effort that I have listed below.
One of the most widely-used methods of monitoring exertion due to its close relation to oxygen consumption. Most individuals have used methods of calculating a heart rate zone based on their theoretical max heart rate (%MHR). This can be done by subtracting your age from 220 and then multiplying it by a certain percentage or percentages to get a range.
For example, for myself, since I am 28 years old, my %MHR would be:
220 - 28 = 192 (Max Heart Rate)
85% x 192 = 163 (Exercising at 85% intensity)
Another heart rate calculation that is also widely-used due to its close proximity to %VO2Max is the Karvonen Method. This is done by first calculating your age-predicted max heart rate (220-age). You then subtract your resting heart rate from this number to get your heart rate reserve (HRR). You then take your HRR and multiply it by your desired exercise intensity and finally add your resting heart rate. Written out, for myself who wants to work at 85% intensity looks like this:
220 - 28 = 192 (Max Heart Rate)
Heart Rate Reserve (HRR) = 192 - 52 (resting heart rate) = 140
85% intensity = (140 x 0.85) + 52 = 171 beats/minute
The Karvonen Method is great to factor in other contributing factors in your overall health. As you can see, using both calculation methods, there is a pretty stark difference between what 85% of my theoretical max heart rate should be (163 vs. 171).
Exercise duration simply refers to the amount of time an exercise session lasts. As mentioned previously, the more intense an individual works, the shorter the duration will be.
For example, exercise that is conducted at an intensity above maximal lactate steady state (approx. 85% VO2 Max) will have a short duration of 20-30 mins. On the other hand, exercise that stays at a steady 70% of VO2 Max can last for an hour or more.
The above image gives some examples as to what each heart rate zone is intended for. I do wish to share one more piece of information that majority of people seem to get confused:
The rate at which your heart works has very little to do with weight loss. Your heart rate may give you an indication (estimated) of how many calories you could be burning, but keep in mind that your heart is not the only organ consuming calories when working out.
Exercising at high heart rates has been shown to be effective at burning lots of calories, but so has lower heart rates (standard resistance training programs). The fact of the matter, and one that I try and remind people is that the most important thing in any training program, with the goal of losing weight, is to be consistent, find something you enjoy, and work as hard as you can 5-6 days a week. Again, you could be working extremely hard, challenging your body and muscles and never get your heart rate up into the "Maximum" zone. That can still be considered effective exercise!