If you're looking to maximize your workout, you might want to reconsider which type of training you do first. While it does depend a bit on your fitness goals (in which case you're probably working with a trainer if you're preparing to run a marathon), the majority of us just want to be healthy and feel comfortable in our own skin. The most efficient method to achieve a tight and toned body is weights first and cardio last. Hitting the weight room before cardio will get you better results and save you time at the gym. Here's why you'll be getting more from your workout if you begin with weights...
Adenosine Triphosphate (ATP)
Every muscle in your body requires a source of energy to function. ATP is what our bodies store and use for energy. There is a long scientific explanation about how adenine nucleotide is bound to phosphates and how these phosphates fuel chemical reactions, but simply put, ATP is the fuel your muscles need to contract. More ATP gets used as the work of the muscle increases, but there is only a limited amount of ATP within each muscle. When it's gone, it has to be replenished to keep the muscles moving.
ATP is so important that it comes from three main systems in the muscle. Only the second two systems are relevant to the topic of weight training before cardio so I'll only touch on those today.
- Phosphagen system
- Glycogen-lactic acid system (anaerobic)
- Aerobic respiration system
Anaerobic system = short duration, high intensity (weights, sprinting)
The anaerobic system breaks down glycogen leaving lactic acid as a consequence. This acid is responsible for the burn you feel while lifting heavy weights or walking up several flights of stairs. Lactic acid builds up in the muscle tissue which causes the soreness you feel after exercising. In order to reach fat burning mode (aka using stored fat for energy), your body needs to first burn off your glycogen stores. Weight training will typically burn all of your glycogen stores quicker than cardiovascular exercise. This means you are instantly in fat burning mode during any cardio you do after weights. This is the main reason why weights before cardio is the most efficient method.
Aerobic system= long duration, medium intensity (jogging)
The aerobic system breaks down glycogen into ATP using oxygen. Using the aerobic system can take up to an hour to go through all the glycogen stored in your cells and liver. This means you're not burning stored fat until an hour into your workout! The important thing to remember is that each molecule of glycogen is broken down into 32 molecules of ATP in the aerobic system, while each molecule of glycogen breaks down into 3 molecules of ATP in the anaerobic system. Clearly the aerobic system is more efficient in terms of generating ATP than the anaerobic system. This is good for sustaining long term exercise, and not so great for getting into fat burning mode quickly. This is why weight training first is better because it allows you to get to the fat burning mode faster than if you had started with cardio.
Begin with weights and deplete glycogen in your cells and liver quicker (putting you in fat burning mode faster). Finish with cardio and burn a much higher percentage of stored fat for the entire duration of your cardio exercise. I recommend 45-minutes of weights, followed by 15- 30 minutes of cardio 3 times per week.