Along with volume, the load is arguably the most important strength training programming variable.
Although high-intensity loads are undoubtedly effective to build muscle and develop strength and power, new research has shown that mixed-intensity training is also effective when following specific programming guidelines.
In the Ozaki study, researchers set out to determine how effective mixed-intensity training is for muscle endurance, hypertrophy and strength in the elbow flexor muscles. To do this, they assigned participants to one of three training loads: three high-intensity (80% 1RM) sets, three low-intensity (30% 1RM) sets, and a single high-load set (80%) with an additional drop set without recovery progressively reducing weight to 30% 1 RM (mixed-intensity training).
Every set in the study was performed until failure. A drop set, utilized in the mixed-intensity group, is a technique where the lifter performs an exercise until failure then immediately reduces the weight load for an additional set or sets. It is important to note that the training volume in the mixed-intensity group was only about two-thirds of the volume in the other two groups.
Nine young previously untrained men performed one of the three strength programs two to three days per week for eight weeks exercising the elbow flexor muscles only. The results of the study showed that a single mixed-intensity set can be as effective as either three sets of high or low-intensity loads to develop elbow flexor muscle cross-sectional area, a direct indicator of hypertrophy, as muscle cross sectional area increased similarly in all three training groups.
However, maximum isometric and 1RM strength of the elbow flexors increased from pre to post in the three-set high-load (80% 1 RM) and mixed-intensity training groups only, indicating the value of the high-intensity of strength training on muscle strength and power development. In contrast, muscle endurance as measured by maximum repetitions at 30% 1RM increased only in the low-intensity load (30% 1 RM) and mixed-intensity groups, demonstrating the value of low loads to muscle endurance.
Overall, the results of the study showed that a single mixed-intensity set strength training program has multiple benefits. It can simultaneously increase muscle hypertrophy, strength and endurance when compared to traditional three-set high- or low-intensity training models that yield either mass, strength, and power, or purely endurance. And mixed-intensity training saves time, as the mean training time per session, including recovery intervals, was lowest in that group.
These results are timely and applicable to sports and fitness training because they show that even with less time spent training and with lower training volumes, a mixed-intensity protocol is as effective a typical resistance training protocols using three sets of high or low loads. The data supported that even with less time spent training and lower overall training volumes, a mixed intensity protocol is an effective, time-saving training method to develop muscle mass, strength, power, and endurance.
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Ozaki H, Kubota A, Natsume T, Loenneke JP, Abe T, Machida S, Naito H. (2018). “Effects of drop sets with resistance training on increases in muscle CSA, strength, and endurance: a pilot study.” Journal of Sports Sciences. Mar; 36(6):691-696.
Amy Ashmore, Ph.D. holds a doctorate in Kinesiology from the University of Texas at Austin. Currently, she is faculty at Florida State University and the author of the upcoming book Timing Resistance Training for Peak Performance (Human Kinetics, June 2019).