The lead author of this paper, Dustin Oranchuk, has a history of publishing some of the best research on tendon remodeling. In this paper, the authors point out that isometric contractions have several advantages over conventional concentric and eccentric exercises. For example, isometric contractions are helpful during acute injuries as the muscle can be exercised in the most pain-free joint angle. This allows for accelerated rehabilitation as extremely large forces can be generated at these safer joint angles. Isometric contractions also allow athletes to focus on specific weak points in their range of motion, which is important for injury prevention and performance enhancement.
Last but not least, the authors cite research showing that isometric contractions induce an analgesic effect, which allows for more aggressive dynamic loading by modifying excitatory and inhibitory corticomotor pathways. Despite clear benefits associated with isometric contractions, there is little consensus in the literature regarding ideal training regimens when incorporating isometric contractions.
To better understand the effects of different types of isometric contractions, the authors reviewed the literature to find detailed information regarding medium-to long-term adaptations associated with different types of isometric training protocols. They specifically evaluated changes in muscle function, shape, neurological recruitment, and performance variables. At the end of an exhaustive review, the authors noted that isometric contractions performed at longer muscle lengths produced greater muscular hypertrophy compared to equal volumes of isometric contractions performed at shorter muscle lengths. The authors state that the results were not surprising since exercising muscles while they are in a lengthened position has been shown to produce greater degrees of blood flow occlusion, which has been shown to stimulate muscle remodeling by enhancing the production of growth hormone. Exercising a muscle in a lengthened position also produces more muscle damage, as the muscles are mechanically inefficient when they are near a full stretch, as their actin and myosin filaments are not fully engaged. The authors finish their review by noting that high-intensity isometric contractions were necessary to improve tendon structure and function, and that exercising muscles while they are in a lengthened position produced a greater transference of strength to dynamic performance.