The term “cutting” refers to a carefully managed phase of nutrition and training designed to reduce body fat while actively working to preserve existing muscle mass. Achieving this requires sustaining a caloric deficit, meaning the body expends more energy than it consumes. Cardiovascular exercise serves as a tool to help widen this energy gap, supporting the primary goal of fat loss. This strategic use of cardio must be balanced against the risk of fatigue and muscle loss, making the amount and timing of activity important.
The Primary Function of Cardio During a Cut
Dietary control remains the most effective method for creating the caloric deficit necessary to lose body fat. Cardio’s role is not to replace this dietary restriction but to act as a supplementary lever for energy expenditure. By increasing the number of calories burned, cardio allows for a slightly larger energy deficit without requiring overly restrictive food intake, which helps make the fat loss phase more sustainable.
Cardio also provides benefits that support recovery and overall training capacity, which are often compromised in a reduced-calorie state. Regular aerobic activity improves cardiovascular health and enhances blood flow to working muscles. This increased efficiency may improve recovery between resistance training sessions, indirectly supporting muscle maintenance.
Establishing Your Cardio Volume
The amount of cardio needed should adhere to the concept of the “minimum effective dose,” meaning doing the least amount necessary to continue seeing fat loss progress. An aggressive approach can lead to excessive fatigue, hindering recovery and compromising performance in resistance training, which is the key stimulus for muscle retention. A sensible starting point is to include two to three cardio sessions per week.
These initial sessions should be short, 20 to 30 minutes, to assess the body’s response and avoid immediate overtraining. This starting volume provides a small caloric buffer while allowing the body to adapt to the energy demands of the cut. If fat loss stalls after several weeks, a small incremental increase in duration—such as adding 5 to 10 minutes per session—is preferable to a sudden, large jump in activity. Total weekly cardio time should not exceed half of the time spent performing resistance training.
Strategic Selection of Cardio Intensity
The choice between Low-Intensity Steady State (LISS) and High-Intensity Interval Training (HIIT) depends on balancing time efficiency with recovery demands. LISS involves maintaining a consistent, moderate pace, typically keeping the heart rate between 50% and 70% of its maximum, corresponding to a Rate of Perceived Exertion (RPE) of 3 to 5 out of 10. This modality is low-impact and places minimal stress on the central nervous system, making it ideal for longer, more frequent sessions or active recovery.
HIIT, conversely, involves alternating short bursts of near-maximal effort (RPE 8-10) with brief recovery periods. While a 15- to 20-minute HIIT session is highly time-efficient and creates a significant post-exercise oxygen consumption (EPOC) effect, it is highly demanding. Because HIIT closely mimics the intensity of weight training, it can contribute more to overall fatigue and may increase the risk of the “interference effect” if performed too frequently or too close to lifting sessions.
Balancing LISS and HIIT
A balanced approach often involves using LISS for higher volume and recovery, reserving one or two HIIT sessions for when time is limited. This strategy allows the benefits of both modalities to be utilized without excessive central nervous system fatigue.
Timing Cardio to Maximize Muscle Retention
The primary concern when combining cardio and resistance training is mitigating the “interference effect,” where concurrent training may blunt strength and muscle gains compared to resistance training alone. To minimize this, the timing of your cardio relative to your weightlifting sessions is important. Ideally, you should separate high-intensity cardio from your lifting by at least six to eight hours to allow different molecular signaling pathways to operate independently.
If separating sessions is not possible, performing resistance training before cardio is generally recommended, as the quality of the strength session should be prioritized for muscle preservation. LISS is the preferred choice for immediate post-lift cardio because its low-intensity nature is less likely to interfere with the anabolic signaling cascade triggered by lifting. While some advocate for fasted cardio, the metabolic advantage for total fat loss over a 24-hour period is minimal. Fasted high-intensity cardio may increase the breakdown of muscle protein, so low-intensity work is a safer choice if training on an empty stomach. Continuous monitoring of recovery metrics, like sleep quality and strength maintenance, is necessary to ensure the cardio volume is not undermining the primary goal of preserving muscle mass.