Fibion Blog • Activation Deficit Is Found – Probably Also From You • Timo Haikarainen

Activation Deficit Is Found – Probably Also From You

Activation Deficit Is Found – Probably Also From You

Activation Deficit Is Found – Probably Also From You

In my work I try to engage in continuous dialogue between science and practice. From my experience of thousands of hours of coaching I would say that an average trainee has activation deficit. It is more about how large the deficit is than whether it exists in the first place. There are also large differences between muscles groups in activation deficit – some muscles are easy to command to work, while other muscles are almost impossible to get working effectively.

In addition, the typical endurance type exercise actually increases this activation deficit. This is rather natural and follows from the training specificity principle. Very effective, ‘simultaneous one time’ motor unit activation is naturally not the best way to go forward in endurance type performance. Although improving activation can paradoxically increase running economy but more about this some other time.

In the next blog we will examine why muscle activation is important even for fat burning and weight loss.

Muscle activation

Figure 1: Greatly simplified description of the muscle activation. Nervous impulse traveling from central nervous system (cross-section of the spinal cord) via peripheral nerves (motor nerve with its end plates) to muscle fibers. In a maximal performance muscle fibers (hopefully) get activated completely commanded by very frequent nerve impulses. Naturally, there are also a lot of impulses going from the muscle to central nervous system, but those are not shown in this drawing. (Figure:


Timo Haikarainen
Timo Haikarainen

Personal Trainer

Fibion Guest Blogger


Connecting sport science research with practical applications

Timo started his coaching and instructing career in 1990s in martial arts, athletics and fitness exercise. From year 2002 he has worked as a gym instructor, personal trainer, and sport coach. Between 2002 and 2008 Timo studied biology of physical activity in University of Jyväskylä, where he graduated majoring in Sport Coaching and Fitness Testing. During the years Timo has accumulated over 15 000 hours of personal training. Practical coaching continues still active even though during last 6 years expert work and education as well as media work in TV and magazines take a big share of his time. Timo is educating personal trainers and gym instructors at SAFE Education, SATS Finland and Sport Center Pajulahti. Timo’s own sport background comes from martial arts, athletics and strength training.