Question: Drew, do you think it is possible to gain muscle mass with isometric training only, assuming a time under tension of 60-90 seconds?
Answer: Yes, it is possible to increase muscular strength and size with only isometric training if you do it with a a high intensity of effort, and a broad range of times under tension can be effective including sets lasting sixty to ninety seconds.
Over the past twenty years I have experimented with a variety of isometric protocols using very different set durations, from Max Contraction Omega sets lasting only a few seconds to timed static contractions lasting up to ninety seconds and many others in between. While different methods of isometrics have their advantages and disadvantages all of them are effective ways to build bigger, stronger muscles.
Isometric exercises do not have to be performed for very long to effectively stimulate muscular hypertrophy. Some of the earliest research on isometrics showed significant strength and size gains could be achieved with a few contractions lasting only six seconds if they were performed with maximum effort (Hettinger, T. and Muller, E. A. Muskelleistung und Muskeltraining. Internationale Zeitschrift fur angewandte Physiologie einschliesslich Arbeitsphysiologie, 5: 1 11-126, 1953) and John Little’s Max Contraction Omega Sets which consist of a few reps of even shorter isometric contractions followed by a partial negative have also been effective for increasing muscle mass. Despite the effectiveness of very brief isometric protocols I recommend using a longer time under tension to allow for a built-in warm-up and to simultaneously stimulate improvements in metabolic and cardiovascular conditioning. I’ve been using sixty to ninety second static holds and timed static contractions on various exercises with many of my personal training clients as well as in my bodyweight high intensity training and timed static contraction training programs
When I last worked with SuperSlow founder Ken Hutchins we trained many people on machines he designed specifically for timed static contraction training which measured and displayed their force input in real time. Clients were instructed to gradually increase the force they applied over a period of ten to twenty seconds up to a specific level and to maintain that for the remainder of ninety seconds. The length of time they were able to maintain their target level of force was recorded, and if they could maintain it until reaching ninety seconds we increased their target the next time they performed the exercise. Using this ninety-second protocol we saw consistent, significant strength increases, and these translated to full-range strength gains when the exercises were performed dynamically as well as visible increases in muscle mass in many trainees.
While the longer isometric contractions were just as effective for improving muscular strength and size – just like a broad range of repetitions can be effective with dynamic exercise protocols – unlike the shorter isometric protocols I’ve experimented with previously they also had a significant metabolic and cardiovascular effect. It was not unusual for clients to experience significant increases in breath and heart rate when performing ninety-second timed static contractions on compound exercises. Also, unlike the shorter isometric protocols the longer timed static contractions did not result in post-workout joint pain or discomfort for some clients, which is reason enough to err on the longer side. I cover the use of timed static contractions and static holds for a variety of exercises in my books Project Kratos and Timed Static Contraction Training.