Hello, this is Sho!
Today, I’d like to talk about a training method that many CrossFit enthusiasts, like yourselves, are probably already practicing—concurrent training. This method is highly popular among athletes and fitness enthusiasts alike, as it allows you to work on both strength and endurance. Personally, it’s one of my favorite training approaches! However, there’s also a potential issue with this style of training, known as the interference effect. This effect suggests that endurance training may interfere with the results of strength training. In this post, I’ll dive into the pros and cons of concurrent training based on recent research and explain how you can effectively incorporate it into your routine.
What is Concurrent Training?
Concurrent training involves combining strength training (resistance training) and endurance training (aerobic training) in the same period or even within the same session. This approach is particularly useful for sports that require a combination of strength and endurance, such as rugby or mixed martial arts. For CrossFit lovers, like myself, we often combine strength work and WODs in the same session, which means we might be engaging in concurrent training more frequently than athletes in other sports.
Concurrent training benefits for CrossFit athletes
The biggest benefit of concurrent training is the ability to improve both strength and endurance at the same time. For athletes, this means they can enhance multiple fitness components simultaneously, making training more efficient. I started concurrent training and CrossFit about two years ago, and I noticed that not only did I gain muscle mass, but my cardiovascular endurance significantly improved compared to when I was doing strength training alone. If you don’t have much time for long training sessions, concurrent training can be a highly effective solution.
Downsides of Concurrent Training
On the flip side, concurrent training has a potential drawback known as the interference effect. This effect suggests that endurance training might reduce the benefits of strength training, potentially limiting muscle growth and strength development. However, I love the CrossFit style of training and refuse to believe it could hinder my gains! (Haha) In the next section, I’ll introduce some research findings that explore this issue and offer insights into how you can enjoy this training style to the fullest.
Research on Concurrent Training
Does endurance training affect muscle growth? Let’s take a look at some key studies that explore the effects of concurrent training:
1. Hickson (1980) Study: Interference of strength development by simultaneously training for strength and endurance.
Hickson’s 1980 study was one of the first to explore the interference effect when combining strength and endurance training. In terms of strength development, the group that performed only strength training (S group) showed continuous improvement over 10 weeks. Meanwhile, the group that combined strength and endurance training (S&E group) saw an increase in strength for the first 7 weeks, but progress stalled in the 9th and 10th weeks, with some even experiencing a decline. For endurance, both the endurance-only group (E group) and the combined group showed improvements in VO₂max. Strength training alone did not significantly affect endurance. Overall, this study suggested that while concurrent training enhances endurance, it may hinder strength development over time, particularly when both types of training are performed for long periods.
2. Schumann et al. (2019) : Compatibility of Concurrent Aerobic and Strength Training for Skeletal Muscle Size and Function: An Updated Systematic Review and Meta-Analysis.
Schumann and colleagues conducted a meta-analysis that looked into the effects of concurrent training on strength, muscle growth, and explosive power. The study found that concurrent training does not significantly hinder muscle growth or maximal strength compared to strength training alone. Interestingly, the type of endurance training (cycling or running), training frequency, participants’ experience, and age did not seem to affect the outcomes. However, when strength and endurance training were performed in the same session, the improvement in explosive power (e.g., jumping ability) was somewhat diminished. Overall, concurrent training is a highly effective way to improve both strength and endurance, but for those focused on maximizing explosive power, it might be better to separate endurance and strength sessions.
3. Wilson, J.M., Marin, P.J., Rhea, M.R., et al. (2012) Study: Concurrent training: A meta-analysis examining interference of aerobic and resistance exercises.
This meta-analysis examined how endurance training (running, cycling) affects the results of strength training. When combining endurance and strength training, the study found that muscle growth (hypertrophy) was slightly reduced compared to doing only strength training, but it was still better than doing only endurance training. High-impact endurance exercises like running tended to suppress muscle growth more than low-impact exercises like cycling. The same pattern was observed with strength gains—endurance training slightly reduced the results compared to strength training alone, but it was still more effective than just endurance training. For explosive power, adding endurance training reduced effectiveness compared to strength training alone. The takeaway is that if you want to maximize both strength and endurance, carefully select the type and frequency of endurance exercises.
4. Kraemer et al. (1995) Study: Compatibility of high-intensity strength and endurance training on hormonal and skeletal muscle adaptations.
Kraemer’s study looked at the hormonal and muscle adaptations when combining high-intensity strength and endurance training. The study involved 35 healthy men, divided into strength training (ST), endurance training (E), and combined training (C) groups. The ST group showed significant muscle growth and strength increases, while the combined group (C) experienced less strength gain, with notable differences in hormonal responses, particularly in the testosterone-to-cortisol ratio. This suggests that concurrent training may lead to reduced muscle growth and a more catabolic (muscle-breaking) hormonal environment.
How to combine strength and endurance training effectively
Based on the research, here are some practical tips for getting the most out of your concurrent training:
1. Adjust the Order and Timing of Your Workouts
If your goal is to improve explosive power (e.g., speed or strength), try separating your endurance and strength sessions by at least 3 hours or even do them on different days. This way, you can maximize the neural activation from strength training and minimize interference from endurance work.
2. Manage Training Frequency and Volume
If your primary goal is muscle growth and strength, limit your endurance training to 2 sessions per week, while focusing on 2-3 strength training sessions. The American Heart Association recommends 150 minutes of moderate-intensity aerobic exercise or 75 minutes of high-intensity aerobic exercise per week for general cardiovascular health.
3. Choose the Right Training Modality
Opt for moderate-intensity, shorter-duration endurance exercises rather than long-duration, high-intensity training like HIIT, which could interfere with your strength gains. Low-impact exercises like cycling may have less of a negative impact on strength training than high-impact exercises like running.
4. Customize Your Training Plan
Tailor your training plan based on your goals, fitness level, and training history. For example, if your current focus is power and strength, reduce the volume or intensity of endurance training. This way, you can maximize your results based on what you’re trying to achieve. I’ve also written an article about a strength training plan, so please check it out. here
Conclusion
While earlier research suggested that concurrent training may have negative effects on muscle growth and strength due to the interference effect, recent findings suggest otherwise. However, if you’re focusing on power development, it’s essential to carefully plan your training program. Ultimately, how much you want to fine-tune your routine is up to you! Enjoy your training, and if you’re aiming for specific results, use the tips from this article to optimize your concurrent training plan.
References
- Hickson, R. C. (1980). Interference of strength development by simultaneously training for strength and endurance. European Journal of Applied Physiology and Occupational Physiology, 45(2-3), 255-263.
- Schumann, M., Feuerbacher, J. F., Sünkeler, M., Freitag, N., Rønnestad, B. R., Doma, K., & Lundberg, T. R. (2019). Compatibility of Concurrent Aerobic and Strength Training for Skeletal Muscle Size and Function: An Updated Systematic Review and Meta-Analysis. Sports Medicine, 52(4), 601-612.
- Wilson, J. M., Marin, P. J., Rhea, M. R., Wilson, S. M. C., Loenneke, J. P., & Anderson, J. C. (2012). Concurrent training: A meta-analysis examining interference of aerobic and resistance exercises. Journal of Strength and Conditioning Research, 26(8), 2293-2307.
- Kraemer, W. J., Patton, J. F., Gordon, S. E., Harman, E. A., Deschenes, M. R., Reynolds, K., Newton, R. U., Triplett, N. T., & Dziados, J. E. (1995). Compatibility of high-intensity strength and endurance training on hormonal and skeletal muscle adaptations. Journal of Applied Physiology, 78(3), 976-989.