Readers of this website will know that I often write about concurrent training research, especially as it affects hybrid athletes. I also like to keep a close eye on research related to these topics. In this article I will be reviewing a brand new research paper that reexamines the dreaded interference effect that many athletes fall victim to, when combining strength and endurance training. As you’ll see, this common problem may be less of an issue than previous studies indicated.
If you’ve done any of my programs, you know that I like to lean heavily on research to make sure that each exercise plan is efficient and effective. This can be very challenging when constructing a hybrid training program.
For years researchers and coaches thought that if you combined strength training with endurance exercise, you would impair your ability to gain strength and lean muscle mass. As with most things in life, that is possible, but there’s a little more to it than that.
More recent research, highlighted in this article, and this one, speak to the importance of separating weight training from cardio sessions by at least 4 hours, to mitigate this negative effect . This training session separation minimizes attenuation in strength and muscle mass. However, researchers have consistently found that there is still some impairment in overall muscle power, or the ability to generate force quickly.
Power production is a crucial element for any athlete. This allows you to sprint, throw a ball, or hip toss a rabid Taylor Swift fan, bent on showing you her latest album.
For those of you with short attention spans, you can check out the overview section below. There I’ve highlighted some of the most important findings about this concurrent training research.
Concurrent Training Research Update
- 12 week study compared training differences between men and women
- Athletes trained HIIT cycling, with heavy strength training
- No evidence of interference effect for strength, size, or explosiveness
- Demonstrated upper body mass gains similar to just lifting
- Found that HIIT cycling and lower body training increased leg mass more than just lifting
This was a well designed study, with a large number of participants. A large sample size matters because it really allows you to determine if there were true differences in exercise conditions, that weren’t just caused by chance.
I also like that they paid a lot of attention to female athletes. Up until this point, most previous concurrent training studies have been done on males only. Without further ado, let’s get to the research study. Don’t forget to join the email list below.
Hybrid Training Research
This research paper entitled, “Neuromuscular Adaptations to Same Versus Separate Muscle‐Group Concurrent Aerobic and Strength Training in Recreationally Active Males and Females,” examined strength and power output adaptations for male and female hybrid athletes, in different muscle groups. The aim of this study was to see if concurrent training paired with lifting in the same muscle groups impaired power, strength, and mass.
The researchers recruited 56 male and 40 female athletes, with moderate training experience. Their average age was in the high twenties. All of them had reasonable strength numbers for newish athletes. The males could squat roughly their bodyweight with the women being closer to half their body weight.
Most importantly, the female athletes were screened for their current menstrual cycle status and the programming was adjusted to run for three full cycles. This helped to control for performance fluctuations that women experience.
Experimental Design
These participants were split into three different groups. Group one did lower body high intensity interval cycling paired with lower body strength training (LHLS). The second group did lower body high-intensity interval training HIIT cycling, with upper body strength training (LHUS). The last group did just upper and lower body strength training (LSUS) as an experimental control group.
The program length was 12 weeks, with athletes in each group working out twice per week. The aerobic and strength training was performed in the same session, alternating which came first between workout sessions. Each session was around 1.5 hours. This was not a high volume program.
The lifts were what you might expect from any intermediate power program. 3×10, 5×5, 5×3, and other similar rep schemes. The 12 week program was split into three 4 week training blocks. Block one was skeletal muscle hypertrophy, two was muscular strength, and three was power production. The aerobic capacity training was a fairly standard 4 min on, 3min off, HITT cycling protocol.
I thought this was a reasonably well designed program that allowed the researchers to examine their specific research questions. Now, let’s get to the results.
Research Results and Interference Effects
Both males and females showed strong improvement in overall strength, muscle mass, and explosive power. Interestingly in a few conditions the groups that did strength training and HIIT, actually showed better gains in muscle mass than the pure resistance exercise groups. Let’s take a look at the significant effect details.
If you want a research based concurrent training program, that will build your muscle strength and fitness. Then check this out below. You can find more information about it here as well.
Concurrent Training and Explosive Power Lower Body
The biggest improvements came when the researchers examined increases in power at the pre intervention 90% of 1RM. Focusing our attention on the back squat, the researchers found that the male lower body lifting and HIIT (LHLS) group increased bar speed by 26% on average. Female LHLS increased by 18% on average.
Interestingly enough, the control groups of males and females (LSUS) increased power at 90% of 1RM by 29% and 20% for males and females respectively. Next let’s look at the upper body, focusing on bench press.
Concurrent Training and Explosive Strength Upper Body
Here we will focus on results at 90% of the original 1RM as well. Males in the upper body strength, lower body HIIT (LHUS) improved power by 39%. Females in this same group improved by 27%. For the control group that just lifted, the males increased power by 34% and females by 38%.
The absolute strength numbers shows a positive effect of roughly 20% improvement for the concurrent training groups. This data shows that, given a longer training period, moderately trained athletes can make big improvements in both upper body strength and power. Now let’s look at muscle gains.
Concurrent Training and Muscle Mass Gains
The researchers examined increases in the pecs, and quads, via ultrasound measurements. The only athletes that increase their quad cross sectional area were the lower body strength and lower body HIIT groups. Males increased by 7%, and females 10%. The pure lifting group made no quad gains.
In terms of upper body muscle fiber, the researchers found that the male group that engaged in upper body strength training and HIIT, as well the control strength group increased their pectoralis mass by 13% and 17% respectively. The females showed no increase in pec mass in any group.
In the next section let’s discuss the practical implications for hybrid athletes, who want to increase their muscle mass, strength, and power. Check out the inforgraphic below, for a great summary.
Concurrent Training Research Recommendations
The biggest take away from this research is that men and women respond similarly to hybrid training programs. There were certainly significant differences, such as in building upper body muscle mass, but that should come as no surprise. Women have less upper body mass than men, and can develop upper body muscle a bit slower.
I would also caution the more advanced athletes reading this article, to interpret these gains with a grain of salt. Remember that these are athletes that have no significant training history. It’s to be expected that they increase strength and power greatly.
I would imagine that athletes with a higher training status might show half the increases that you saw for the newer athletes in this study. If you’re closer to your genetic limit, in strength development, your gains are smaller.
Most importantly this research shows that you can still gain significant power in both the upper and lower body, when performing weight training, with HIIT cycling.
I found it particularly interesting that they increased so much considering that all aerobic training and lifting was done in the same session. Recall that half of the sessions had the athletes doing the cardio first, which most research shows, limits power production, and muscle growth. It’s possible with a better exercise program design they could have increased even further.
In the next section I’m going to recommend some lifting programs for hybrid athletes. However, if you want to try my most popular hybrid training program, then you should follow this link to learn more about it. You can also pick up your copy below.
Concurrent Training Programs
I’ve written a lot of hybrid and concurrent training programs over the years, and these are some of my most popular. I recommend clicking on few links to see which ones are a good fit for your exercise goals. There are programs that are good for untrained individuals, all the way up to elite athletes.
- 6 Week Beginner Hybrid Training Program
- 12 Week Beginner Hybrid Program
- 8 Week Hybrid Hypertrophy Program (Size + Conditioning)
- 8 Week Hybrid Strength and Endurance Training Plan (Part 1)
- 8 Week Hybrid Strength and Endurance Training Plan (Part 2)
- 8 Week Hybrid Bodybuilding and Endurance Training Program (Part 1)
- 8 Week Hybrid Bodybuilding and Endurance Training Program (Part 2)
- 12 Week Apex Hybrid Performance Fitness Plan (Part 1)
- 12 Week Apex Hybrid Performance Fitness Plan (Part 2)
Final Thoughts
While this research is very well done, with good controls, it only answers the questions it specifically asked. We still don’t know if moderate intensity aerobic exercise, like Zone 2 training, would attenuate power production. Similarly we don’t really know what specific power training movements would do when paired with aerobic exercise. I’m guessing that they would be key for well trained athletes to avoid negative impact on power.
I would also like to see future research on hybrid athletes that examines the effect that a low or high volume resistance training program has when paired with cardiovascular training.
I’m sure there will be further research studies on these topics, but I think it’s safe to say that as we see more research on the topic, we are finding out that you can increase strength development, muscle power, and mass, if you follow a structured program that integrates cardio smartly.
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