Rate of Force Development (RFD) by Chris Juneau SPRINZ

Rate of Force Development (RFD) and why physiotherapists should know about it.

Chris Juneau, Physiotherapist PT, DPT, SCS, CSCS, Board-Certified Clinical Specialist in Sports Physical Therapy (SCS)

Certified Strength and Conditioning Specialist (CSCS)

Dry Needling Certified &USA Weightlifting Coach

Sports Performance Research Institute NZ, Auckland University of Technology.

There is no question that objective data, repeated testing, and functional assessments

are taking medicine by storm. The concept of profiling individuals’ capacity, both at a tissue and compound task level, have become common processes in justifying progression through a rehabilitation program, to reintegration into activity after injury, or in assessing risk factors in screening avenues. The most commonly utilized testing mediums in the Physiotherapy world typically involve either peak force, or maximal strength, (think in terms of a hand held dynamometer or manual muscle test), or multi-joint functional tasks (single leg hop testing after anterior cruciate reconstruction or the timed up and go assessment in a fall-risk population). While these tests are certainly valuable, there is an emerging interest in the concept of force and time, specifically the ability to produce force quickly, which seems to better represent the comprehensive capacity of an individual and better predict performance.

This category of force-time characteristics is often called rate of force development (RFD), which simply describes the force produced for a given period of time.

Let me explain a bit more about why this is potentially more valuable than maximal strength.

If you consider an individual walking down a sidewalk and stumbling over a bump in the pavement, ask yourself what is more important related to recovering the tripped limb and preventing a fall:

1 - the ability to produce a maximal hip flexion force or 2 - the ability to produce a hip flexion contraction quickly.

It should get your mind spinning a bit, specifically considering the fact that this person would need at least enough strength to pull their leg forward, but ultimately, that value is certainly not a maximal effort for most individuals, which brings us to RFD. It should make a bit of sense to consider that moving quickly, recovering their leg via a rapid hip flexor contraction, will provide a better chance of preventing the fall by moving their leg quickly under them.

information when describing risk, or readiness, after

injury or in a performance environment, as

increases in RFD are also associated with

improvements in performance in numerous

activities such as sprint speed and weightlifting capacity , along with tasks of daily living, such as

increases in walking speed or sit to stand activities.

Below is a list of how RFD impacts activity:

Slawinski J, Bonnefoy A, Leveˆque J, et al. Kinematic and kinetic comparisons of elite and welltrained sprinters during sprint start. J Strength Cond Res. 2010;24(4): 896–905.

Stone M, Sands W, Carlock J, et al. The importance of isometric maximum strength and peak rate-of-force development in sprint cycling. J Strength Cond Res. 2004;18(4): 878–884.

Mirkov D, Nedeljkovic A, Milanovic S, et al. Muscle strength testing: evaluation of tests of explosive force production. Eur J Appl Physiol. 2004 91:147–154

Clark D, Manini T, Fielding R, et al. Neuromuscular determinants of maximum walking speed in wellfunctioning older adults. Exp Gerontol. 2013; 48:358–363.

Now, I know what you are thinking, this sounds

fancy and most certainly will cost a large investment, which is not very appealing, and I would certainly sympathize with that. Our current model involves using expensive machines, such as force plates and isokinetic dynamometers, and these tools are fantastic for research and academics, but not for clinical settings. Well, good news! Part of my time here in New Zealand is working with AUT to investigate easier and more practical avenues for collection of this data. The goal is to provide a cost effective, reliable, testing device that can help provide more information

If you would like to read a bit more about RFD here is a really great resource:

Maffiuletti N, Per Aagaard P, Blazevich A. Rate of force development: physiological and methodological considerations. Eur J Appl Physiol. 2016; 116:1091–1116.

about the capacity of your clients, in an attempt to improve our profiling, and more objectively quantify the performance of specific tissues, movements, and tasks.

My research question revolves around the use of a load cell, often referred to as a strain gauge, which is the big brother to a hand held dynamometer, but significantly more practical and portable than a force plate or isokinetic device, and how it can be used in clinical settings to acquire RFD.

First things first, my aim is to assess the reliability of the tool and the set-up, which is important to make sure we have consistency in the data capture, and eventually compare performance of a healthy group to an unhealthy group. My principle measure is knee extension (quadriceps function) and my unhealthy population will be a cohort of individuals with anterior knee pain. Essentially, I want to look at the RFD differences in both individuals with and without anterior knee pain, but

also look at differences between the painful and nonpainful limbs in that same cohort. This could start providing more useable, activity relevant, and reliable data for everything from return to sport testing to fall risk assessments.

Needless to say, I will need participants when it is time to collect data, if you are interested, please contact me via email and we can set up a time to chat!

Cmj027@gmail.com

Chris is a Sports Residency and Sport Performance Trained, Doctor of Physical Therapy from the United State of America, with a unique perspective on strength and conditioning, performance, and sports injury management. Having practiced the last 9 years in outpatient sports orthopedics, Chris has recently left his position with Memorial Hermann Ironman Sports Medicine in Houston, Texas, to pursue a Masters of Philosophy (Rehabilitation Science focus) in Auckland, with AUT SPRINZ. Chris completed his sports training and education with The University of St. Augustine, The Ohio State University, and University of Louisville.