Building Endurance in Strength Athletes

Many strength athletes avoid cardio, fearing they will lose muscle and strength. But low aerobic fitness slows recovery, limits training volume, and harms the heart. The editorial team has looked into how real the “interference effect” is and how to build endurance without harming strength results.

Why a strength athlete needs endurance

Among powerlifters and bodybuilders, the belief is still popular that cardio “burns muscle” and hinders progress in strength. Because of this, many strength athletes have low aerobic fitness: shortness of breath after a few flights of stairs, a high resting heart rate, and slow recovery between sets.

Meanwhile, aerobic endurance brings strength athletes both practical and medical benefits. A better aerobic base speeds recovery between sets and workouts, allows a greater volume of work to be performed, eases control of body weight, and supports cardiovascular health.

Cardiorespiratory fitness is one of the strongest predictors of overall health and life expectancy. The ACSM position on the quantity and quality of exercise recommends that adults do regular aerobic activity regardless of other goals. The strength athlete, especially in the heavy weight classes, is not exempt from it.

It is worth mentioning separately athletes who use anabolic drugs: in this group the risks to the heart are higher, and aerobic fitness together with medical monitoring is even more important. At the same time, cardio does not neutralize the harm from the drugs.

The interference effect: myth or reality

The concept of the “interference effect” appeared after Hickson's classic 1980 study: participants who combined a very large volume of strength and endurance training at a certain point stopped progressing in strength compared with a strength-only group. Since then this idea has often been exaggerated.

A 2012 meta-analysis by Wilson and colleagues showed that concurrent training can reduce gains in strength, hypertrophy, and especially power, but the effect depends on the type and volume of aerobic work. Running was associated with greater interference than cycling, and increasing the frequency and duration of cardio intensified the negative effect.

An updated 2022 meta-analysis by Schumann and colleagues concluded that combining aerobic and strength training generally does not hinder gains in muscle mass and maximal strength, though it may reduce the development of explosive strength, especially when both types of training are performed in one session.

In other words, interference is a real phenomenon, but for most strength athletes a moderate volume of properly organized cardio poses no threat. Problems begin with large volumes, daily running, or exhausting intervals before heavy strength workouts.

Which kinds of endurance to develop

For a strength athlete it helps to distinguish the aerobic base from specific endurance. The aerobic base is the ability of the heart, blood vessels, and muscles to perform moderate-intensity work for a long time. It develops with long steady work at a conversational pace.

Specific endurance is the ability to maintain quality of work throughout a workout: many sets, short rest, repeated efforts. It is partly developed by strength training itself but is well complemented by interval work.

The “polarized” intensity-distribution model, described by Seiler for endurance sports, assumes that most work is done at low intensity and a small share at high intensity. Strength athletes can adapt this idea: the base is light cardio, and intervals are dosed.

The choice of tool also matters. Cycling, uphill walking, rowing, or the elliptical have less impact and eccentric load than running, so they fatigue the legs less and interfere less with squats and pulls.

How to combine cardio with a strength program

The simplest rule is to space heavy strength training and intense aerobic work apart in time. If both fall on the same day, an interval of a few hours between them reduces their mutual negative effect.

• start with 2–3 sessions of light cardio of 20–30 minutes per week;
• choose low-impact tools: cycling, walking, rowing;
• do not schedule intense leg intervals the day before a heavy squat or pull day;
• if strength and cardio are on the same day — strength first, when strength is the priority;
• increase the volume of aerobic work gradually, watching your strength metrics.

As for the order within a single session, a 2018 meta-analysis by Murlasits and colleagues showed that performing strength exercises before aerobic ones gives a slightly greater gain in lower-body strength, while the order did not significantly affect aerobic capacity.

Heart rate is a convenient guide. For “base” work, an intensity at which you can talk freely is enough. Such work barely hinders recovery and may even improve it thanks to increased circulation.

Short complexes for specific endurance — for example, sled pushes, kettlebell carries, or circuit work with light weights — can be placed at the end of a strength workout or on a separate light day.

Tracking progress and safety

To understand whether the aerobic part is working, it helps to choose simple metrics: resting heart rate in the morning, heart rate at a standard load (for example, on a stationary bike at a fixed power), and heart-rate recovery time after a set. A decline in these metrics indicates improved aerobic fitness.

In parallel, you need to watch your strength metrics. If after adding cardio your working weights decline for several weeks in a row, the volume or intensity of the aerobic work should be reduced or moved to another day.

Athletes with large body mass, elevated blood pressure, excess weight, or a history of anabolic drug use should undergo a medical examination before beginning intense cardio loads: ECG, blood-pressure measurement, and if needed echocardiography and a stress test.

Chest pain, sudden shortness of breath, dizziness, or a sensation of irregular heartbeat during exercise is a signal to stop immediately and see a doctor. This applies to everyone, regardless of fitness level.

Editorial conclusions

Aerobic endurance is beneficial for strength athletes: it speeds recovery, allows a greater volume of work to be performed, and supports heart health.

The interference effect is real, but it appears mainly with large volumes, running, and intense work right up against strength training. Moderate low-impact cardio, spaced apart in time from heavy sessions, barely hinders progress in strength and mass.

You should start with a few light sessions a week and increase the volume gradually, monitoring heart-rate and strength metrics.

We also recommend our articles on powerlifting and bodybuilding, on functional training, and on the deload week.

References

1. Hickson RC. Interference of strength development by simultaneously training for strength and endurance. Eur J Appl Physiol Occup Physiol. 1980;45(2–3):255–263.
2. Wilson JM, Marin PJ, Rhea MR, et al. Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises. J Strength Cond Res. 2012;26(8):2293–2307.
3. Schumann M, Feuerbacher JF, Sünkeler M, et al. Compatibility of concurrent aerobic and strength training for skeletal muscle size and function: an updated systematic review and meta-analysis. Sports Med. 2022;52(3):601–612.
4. Murlasits Z, Kneffel Z, Thalib L. The physiological effects of concurrent strength and endurance training sequence: a systematic review and meta-analysis. J Sports Sci. 2018;36(11):1212–1219.
5. Seiler S. What is best practice for training intensity and duration distribution in endurance athletes? Int J Sports Physiol Perform. 2010;5(3):276–291.
6. Garber CE, Blissmer B, Deschenes MR, et al. American College of Sports Medicine position stand. Quantity and quality of exercise for developing and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in apparently healthy adults. Med Sci Sports Exerc. 2011;43(7):1334–1359.