Here’s a topic suggested on my “Ask Dave” page.
Can I combine my cardio and weight baring exercises?
My current personal trainer has me doing planks, lunges, squats, pushups and crunches.
I usually run to the park and do them there and run back but he has advised me this is not good… can you tell me otherwise?
Yes and no! In my opinion any combination of exercise is good, but there is good exercise and then better exercise. Different exercises and combinations of exercises can produce different results, and the results can vary from one individual to another.
Your trainer probably has good reasons in mind for recommending separating your cardiovascular and resistance training workouts, both in regard to general exercise strategy as well as what is best suited to you as an individual.
Generally speaking, the point of resistance training is to exhaust the targeted muscle groups, leading to increased muscle mass. There are varying benefits as a result of this increased muscle mass, such as increased strength, increased metabolic rate and so forth. Depending on the distance to the training location, a jog or run could be considered a suitable warm up, increasing heart rate and blood flow to working muscles. The issue I see here is that running at an intensity or duration in excess of what is required as a warm up will be burning up glycogen stores within the muscles, which we would be counting on as a fuel source to perform our resistance exercises to our best potential and thus achieve the greatest possible results.
The situation is similar upon completion of the resistance training, when a short jog home might be considered a good “cool down” period. Opinions vary on training cardio immediately after resistance training, but I am of the belief that it is important to replace glycogen stores and also consume protein as soon as is reasonably possible after completion of training. Once these glycogen stores are depleted, the body can enter a catabolic state, breaking down muscle tissue and converting it to glycogen. In other words, by training cardio after resistance training we may be squandering the results and reducing the amount of muscle growth.
There is another school of thought that since we have used up our energy stores on resistance training, by going straight into cardiovascular we may force the body to burn fat stores as a fuel source. For this reason a trainer may often program sessions in the format of a warm up, then resistance training, and then some form of cardio training.
Unfortunately bodybuilding is still not an exact science with hard & fast rules, so the answer is to choose the approach that seems to make the most sense, objectively assess your results, and then consider if a different approach may be more suitable for you. Again, every person responds differently and this is an ongoing process.