When it comes to structuring a workout routine, the order in which you perform different types of exercises can significantly impact your results. One common debate in the fitness world revolves around the question of whether to do cardio before or after lifting weights.

Understanding Energy Systems

To comprehend why cardio before lifting can lead to lower body fatigue, we must first delve into the energy systems our bodies rely on during different types of exercise.

1. Aerobic Energy System: Cardio exercises, such as running, cycling, or brisk walking, predominantly utilize the aerobic energy system. This system relies on oxygen to produce energy and is highly efficient at sustaining activity over extended periods. It primarily engages the lower body muscles, like the quadriceps, hamstrings, and calf muscles.

2. Anaerobic Energy System: Weightlifting and resistance training primarily use the anaerobic energy system. Unlike the aerobic system, the anaerobic system doesn't rely on oxygen and provides short bursts of intense energy. It targets various muscle groups, including those in the upper body like the chest, back, and arms.

Now, let's explore why cardio before lifting tends to fatigue the lower body more:

1. Depletion of Glycogen Stores: When you perform cardio before lifting, your body primarily relies on glycogen stores for energy. Glycogen is stored in muscles and the liver, and it's the primary source of energy during aerobic exercises. As you engage in cardio, your lower body muscles use up a significant portion of glycogen, leaving them partially depleted before you even start lifting weights.

2. Muscle Recruitment: Cardio exercises mainly involve repetitive, sustained movements that target the lower body muscles. When you transition to lifting weights immediately after cardio, these already-fatigued lower body muscles are recruited to stabilize your body during compound movements like squats or deadlifts. This added demand on tired muscles can lead to a feeling of weakness and fatigue.

3. Central Nervous System Fatigue: The central nervous system plays a crucial role in muscle activation and coordination. Cardio workouts can cause central nervous system fatigue, making it challenging to maintain proper form and generate force during weightlifting exercises. This can result in suboptimal lifting performance, especially in the lower body.

Recommendations for Optimal Performance

If you want to minimize lower body fatigue when combining cardio and weightlifting, consider the following recommendations:

1. Separate Sessions: Perform cardio and weightlifting on separate days or during different sessions within the same day. This allows your lower body muscles to recover between activities.

2. Prioritize Your Goals: Determine your primary fitness goals. If you aim to improve cardiovascular endurance, starting with cardio may be beneficial. However, if muscle building or strength gain is your priority, consider lifting first.

3. Warm-Up and Cool Down: Regardless of the order, always include a proper warm-up and cool-down in your routine. A dynamic warm-up can prepare your muscles and nervous system for both cardio and lifting.