Understanding Mechanical Tension in Strength Training
Mechanical tension is a key concept in strength training that often gets misunderstood. At its core, mechanical tension refers to the force that stretches muscle tissue during resistance training. Every workout involves three key phases: eccentric isometric and concentric. While mechanical tension is present in all three, it’s often associated most with the concentric phase, the part where muscles contract to overcome resistance, like when you’re lifting the weight.
Here’s where it gets interesting - takes much less force to perform isometric holds or eccentric movements compared to the concentric phase. That’s why you can usually handle more weight when lowering a load or holding a position, like in programs that emphasize these movements. Cal Dietz’s Triphasic training focuses on targeted muscle contractions like eccentrics, isometrics and concentrics. You can lower more weight under control during eccentric movements and hold a load in an isometric contraction, but when it comes to lifting the weight, actually fighting against gravity, you’re significantly weaker. This is the concentric phase, and its where mechanical tension comes into play.
When training for mechanical tension, the goal is to push the muscle to its limits during the concentric phase. Yes, isometric holds and eccentric movements fatigue the muscle and create tension, but the real challenge, and growth, happens when you can no longer lift the weight. That’s when the muscle hits failure, which is the sweet spot for maximizing strength and hypertrophy. You’re not just moving the weight; you’re pushing through resistance until your body can’t go any further, and that’s the stimulus your muscles need to adapt and grow.
So, while it’s important to incorporate isometric holds and focus on lowering weights with control (eccentrics), the heart of mechanical tension lies in reaching muscle failure during the concentric contraction. This is where true muscle growth happens, when you push your muscles to their absolute limit and create the conditions for them to rebuild stronger and bigger.
John Welbourn is Founder/CEO of Power Athlete Inc and former NFL player. John was drafted with the 97th pick in 1999 NFL Draft and went on to be a starter for the Philadelphia Eagles from 1999-2003, appearing in 3 NFC Championship games, and started for the Kansas City Chiefs from 2004-2007. In 2008, he played with the New England Patriots until an injury ended his season early with him retiring in 2009. Over the course of his NFL career, John started over 100 games regular season games with 10 play-off appearances. He was a four-year letterman while playing football at the University of California at Berkeley. He graduated from the college of letters and sciences with a bachelor's degree in Rhetoric in 1998. And did his Masters work at the UC Berkeley School of Education in 1999. Since retiring from the NFL, John has worked extensively with the NFL, NHL, MLB, Olympic athletes, the US Army and Naval Special Warfare. He works as a consultant and advisor for several companies focused on improving human performance through training, nutrition and fitness-based technologies. John provides daily coaching and mentorship to over 5000 athletes around the world through his Power Athlete Coaches Network and training program delivery platform. Since in 2013, John has hosted a weekly podcast, Power Athlete Radio; a podcast dedicated to improving performance and connecting with some of the smartest people on the planet. With more than 700 episodes Power Athlete Radio has proven to be on the top podcasts in the strength and conditioning realm. John travels the world lecturing on performance and nutrition for Power Athlete and as a keynote speaker. John is a married father of three and resides in Austin, Texas. You can catch up with him at his personal blog, “Talk To Me Johnnie”, at Power Athlete or on social media @johnwelbourn.