By Emma Garrett, Physiotherapist
In the sports of strength training, whether Olympic weightlifting, powerlifting or bodybuilding, there's often a feeling of anxiety that concurrent cardio (endurance) training will limit strength gains. However, take Olympic weightlifting and Crossfit as an example, some of the strongest athletes are also the best athletes in cardiovascular fitness. Tia-Clair Toomey won gold at the 2018 Commonwealth Games in weightlifting (a strength dominant sport), and she is also a five-time winner of the Crossfit games (which require both endurance and strength).
So what does the research say in terms of concurrent strength and endurance training?
Whether an athlete should undertake concurrent weightlifting and cardiovascular training is highly dependent on a multitude of factors, including their training goals, recovery, total training hours, etc. We’re going to have a look at the effect of concurrent training on various training outcomes, including power, strength, hypertrophy and fat loss.
Whether an athlete should undertake concurrent weightlifting and cardiovascular training is highly dependent on a multitude of factors, including their training goals, recovery, total training hours, etc.
Different training goals
Power is the ability to produce force quickly. It's the main variable that is impacted by concurrent strength and endurance training. Thus, if an athlete’s sport requires high amounts of power, such as Olympic weightlifting, then concurrent endurance training should be limited.
Theoretically, there is minimal overlap between power training and long-duration endurance training in terms of the demands on the body. However, there is some overlap between short-duration high-intensity sprinting and power weightlifting training. One study found that short duration, high intensity sprinting did not reduce strength or power, while still increasing VO2 max. A second study found that short-duration sprinting increased power more than low-intensity endurance exercise, and this is likely due to the overlap in sporting demands.
In terms of body fat, the greatest decrease in body fat occurs with concurrent training, particularly when high-intensity endurance exercise combines with strength training. Essentially, the higher the intensity of the cardiovascular endurance training, the greater the body fat loss. Additionally, metabolic rate after exercise also increases exponentially with increasing exercise intensity.
In terms of muscle mass, high intensity training does not appear to reduce muscle mass, compared to traditional endurance exercise. If fat loss is the priority, running has shown to result in the largest decrease in body fat, more so than cycling. However this was at the cost of smaller increases in hypertrophy and strength, compared to other training modalities. In terms of strength training, to maximise fat loss, it is more effective to combine it with endurance training.
For maximum strength and hypertrophy, the research suggests that concurrent training does not lead to a significant reduction in progress, as long as an appropriate training modality for endurance is selected. In fact, some of the research suggests that quadriceps hypertrophy occurs to a greater extent when training concurrently in aerobic and resistance exercises.
Different types of training
The style of endurance training should match the athlete’s other sport as closely as possible to allow the body’s adaptations to be as similar as possible.
For example, a hockey player who is aiming to increase leg strength should select cycling over running since it is more similar to skating. Another possible reason for this is that running has a higher eccentric component, compared to cycling which is mostly concentric, and running generally has greater increases in muscle damage than cycling, however further research is needed in this area.
The style of endurance training should match the athlete’s other sport as closely as possible to allow the body’s adaptations to be as similar as possible.
Amount and frequency of training
For strength/power athletes, they should select endurance activities that are performed at very high intensities, as the research has shown this results in lower decrements in hypertrophy, strength and power. Additionally, they should avoid endurance training that is greater than 20-30 minutes that is performed greater than 3 days per week. Furthermore, it is best if strength and endurance training is separated throughout the day by at least 6 hours, with the resistance training occurring earlier in the day. Ideally, complete the strength and endurance training on separate days.
Finally, this interference effect appears to be mainly body part specific, as the reductions in strength were found in the lower body but not the upper body, after a primarily lower body endurance activity. Thus, if an individual is looking to improve upper body strength, if they choose a lower body endurance activity such as cycling, there should be minimal interference.
The effect size of strength, power and hypertrophy does appear to be dependent on the number of days per week of endurance training. As shown below, when the number of days of endurance training increases, the greater the decrements in strength, power and hypertrophy. Despite the increasing effect size, there is still an overall improvement in each criteria, albeit slightly reduced than if endurance training was not performed.
In addition, the effect size decreases as the minutes of endurance training completed per day increases. Thus, as endurance training time increases, the decrements in strength, hypertrophy and power increase. Again, while there is a significant decrement, there is still an overall net improvement in hypertrophy, strength and power (with the exception of power when 50-60 minutes of endurance training is completed).
If the main goal is endurance training, then additional strength training can be incorporated without reducing aerobic capacity.
Summary
Overall, muscle hypertrophy, strength and endurance are not significantly affected by concurrent training. Power is more significantly affected so if you are involved in a sport that requires a significant power output, such as Olympic weightlifting, it may be worth limiting endurance training. If you are looking at combining training modalities, here are a few takeaway points to best do this.
Choose the style of endurance training that best matches your other sport to allow the body’s adaptations to be as similar as possible, ie. avoid competing adaptations.
Short, high-intensity endurance training (eg. HIIT) combined with strength training is best if your goals are fat loss.
Avoid endurance training that is greater than 20-30 minutes, 3+ days per week if you’re looking to improve muscle strength/hypertrophy.
For those primarily interested in endurance training, additional strength training won’t reduce aerobic capacity.
The interference effect for strength training appears to be body part specific so ideally separate muscle groups for cardio and strength training.
Ideally 6 hours between strength and endurance sessions if done on the same day, or 24 hours between sessions.
Complete strength training prior to endurance training if doing both on the same day.
References
Hickson, R.C., Interference of strength development by simultaneously training for strength and endurance. Eur J Appl Physiol Occup Physiol, 1980. 45(2-3): p. 255-63.
Wilson, J.M., et al., Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises. J Strength Cond Res, 2012. 26(8): p. 2293-307.