Introduction to Isometrics and PNF

Danny Lum is a Singaporean strength coach and sport scientist specializing in applied performance research. His work explores strength diagnostics, isometrics, and power development, and he is widely published and recognized for connecting sport science with practical coaching. In this episode, Danny explores the intersection of sport science and real-world performance. Danny shares insights from his research on isometric training, PNF stretching, and velocity-based training, emphasizing how different methods complement rather than replace one another. The conversation dives into squat depth, unilateral vs. bilateral training, and the role of variability in power development. Throughout, Danny highlights a key theme: effective training is individualized, phase-dependent, and built on understanding how the body adapts. Today’s episode is brought to you by Hammer Strength. Use the code “LILAJUSTFLY10” for 10% off any Lila Exogen wearable resistance gear. For this offer, head to Lilateam.com Use code “justfly10” for 10% off the Vert Trainer View more podcast episodes at the podcast homepage. (https://www.just-fly-sports.com/podcast-home/) Timestamps 0:00 – Welcome to the Show 2:42 – Journey to Sprinting 5:10 – Strength Training Insights 14:38 – The Power of Isometrics 15:44 – PNF Stretching Explained 24:54 – Programming Isometrics 28:46 – Unilateral vs. Bilateral Training 36:33 – Velocity-Based Training 44:20 – The Importance of Variation 52:42 – Research on Isometric Strength 1:07:38 – Yearly Training Plan Danny Lum Quotes "When you lift heavy weights, if you have maximum intent, even though the external movement looks slow, there is rapid neural firing. It doesn't necessarily mean that slow movement during heavy lifting means you are not having a fast neural firing, which is relevant to sprinting." "For sprinters, when the knee is lifted up at the highest point, they don't just allow the leg to drop passively. They actually start developing force and hammer down right from the highest point. That is where your hip flexion angle is about 90 degrees. So if you're not strong at that position, then you're not maximizing the amount of force you can develop through the full range of movement." "If you're going to do static stretch during your warm-up, you might as well just perform isometric contraction at that position as well. That helps to not only activate your muscle, but you actually microdose isometric training every day." "You're strengthening your muscle at the long muscle length, and that long muscle length is where the muscular-tendinous system is most vulnerable. If you are not strong at that range, then your risk of injury just increases. But if you can get yourself stronger at the long range, you're actually protecting yourself." "If we are talking about loading the tissue itself...loading the muscle and tendon tissue, then doing unilateral work is probably going to benefit more because you can actually load the quads more by doing single-leg squat as compared to double-leg bilateral squat." "Having a variety of load actually gives greater adaptation. I think that why that's the case is because you allow the person to have a little bit of velocity focus and a little bit of force focus in the training." "If I contract rapidly, and I sustain for three seconds, because that allows me to build to a higher peak force, my strength actually increased more, and I also significantly increased my rate of force development. It allowed me to get the best of both worlds; both rate of force development and peak force actually improved." "Isometrics actually improved running economy more than plyometrics. My theory behind it is that runners, while they are running, is sort of like a low-intensity plyometric. So with a higher-intensity plyometric versus isometric, which is a totally new stimulus, they actually adapt more with the new stimulus as compared to plyometrics." "Today, the athlete might be able to lift 100 kilograms for five reps before he feels fatigue, and on a bad day, three reps. If I standardize in the program five reps every day, then on some days he might be overtraining, and that’s where velocity training provides the advantage. I’m still getting him to lift at his daily maximal of effort, but it’s self-regulated." "I don't really go too movement specific. Usually, I'll be more general in that sense because I prefer to build up the physical capacity rather than being overly specific. But having said that, most of the exercises have to be relevant to how they function." "Isometric training is probably the best way to improve angle-specific force generation capability. On the other hand, we also know that tissue adaptation is greater when training at longer muscle length. So you're actually stretching the muscle and the tendon a little more, and that will result in greater improvement in hypertrophy as well as greater tendon stiffness." "As they’re closer to the major competition, I’ll replace the dynamic heavy lifting with isometric training. I won’t replace everything, but I’ll replace part of it just so that they can recover better with a lower level of fatigue, so that leading up, they won’t have a fried central nervous system." About Danny Lum Danny Lum is a Singapore-based strength and conditioning coach and sport scientist known for his work in applied performance research and athlete development. He has held roles in both academic and high-performance sport settings, blending research with practical coaching. Danny’s work focuses on areas such as strength diagnostics, isometric training, unilateral vs. bilateral force production, and optimizing power for sport. He is widely published in peer-reviewed journals and is a frequent presenter at international conferences, bridging the gap between sport science and real-world coaching practice.