High-load resistance training has always been linked to greater muscular power and strength, while low-load training can lead to greater muscular endurance. Breaking that down further, high-load resistance training can increase adaptations in the myofibrils, while low-load endurance training concentrates on the mitochondria, the powerhouses of the cells.
One took a closer look at the two resistance training methodologies to determine which would lead to better overall results. As the paper stated, "concurrent practice of traditional endurance exercise and resistance exercise regimens to achieve both types of muscle adaptations is time-consuming, motivationally demanding, and contended to entail practice at intensity levels, that may not comply with clinical settings. It is therefore of principal interest to identify effective, yet feasible, exercise strategies that may positively affect both mitochondrial and myofibrillar protein turnover."
Recent studies have indicated that low-load resistance training can be as effective for increasing myofibrillar accretion and muscular growth. At the same time, high-load resistance training can also increase mitochondrial biogenesis, though to a lesser degree than low-load endurance training.
Regarding mitochondrial stimulation, low-load endurance training has proven the more effective methodology. One study on endurance training recorded "a robust increase in mitochondrial protein synthesis rate after low-load resistance exercise performed with a slow and tonic contraction phase and conducted to volitional fatigue."
Not only that, but endurance training has been linked to higher ATP energy turnover in comparison to high-load training. Also, "fatiguing low-load resistance exercise conducted with slow and tonic contraction phase or application of external restriction of blood flow to the exercising muscle, has been shown to impose a more pronounced decrease in tissue oxygenation compared to traditionally performed high-load and low-load resistance exercise."
Low-load, endurance training delivers the same, or better, results as high-load training, but with far less strain on your body.
Low-load, endurance training is less mechanically strenuous, reduces the amount of time required to reach volitional fatigue, reduces the required work volume, and stimulates muscle growth on par with high-load training. Simply put: endurance training delivers the same, or better, results as high-load training, but with far less strain on your body.
Regarding sheer mechanics, low-load endurance training is the clear winner over high-load resistance training. Though there is a certain amount of discomfort (that burn in your muscles when you're hitting 15-20 reps), it's very likely more effective for both mitochondrial and myofibril adaptations.
1. Groennebaek, Thomas, and Kristian Vissing. “.” Frontiers, Frontiers, 4 Sept. 2017.