“Theory has to comply with experimentation 100% of the time. If there is even one instance where theory does not comply with experimentation, than the theory either has to be thrown out or changed to incorporate the new information. In science, experimentation trumps all.” – Ryan Hall
In the comments following a previous post about negative emphasized repetitions someone brought up that Ryan Hall debunked the inroad theory of growth stimulation and there was a request for his comments on this. I asked and received permission from Ryan to share something he wrote about this previously, which follows.
I will be interviewing Ryan on this topic next week, so if you have questions about this please post them in the comments section below. I will not be addressing the questions in the comments section here, but they will be included in my interview with Ryan which will be posted next week.
As you and I have discussed on the phone before, the concept of inroad is extremely flawed and not indicative of what is actually occurring physiologically. I wish I could take a shot-gun and blow the concept of inroad away, but I guess the written word accompanied by supporting data will have to suffice. Concentric failure or short term muscle fatigue is not necessarily indicative of microtrauma / long term force decrement, as evidenced by the following studies:
Development of T-tubular vacuoles in eccentrically damaged mouse muscle fibres
Ella W. Yeung, Christopher D. Balnave, Heather J. Ballard, J.-P. Bourreau and David G. Allen
Journal of Physiology(2002), 540.2, pp.581Â–592
Vacuole formation in fatigued skeletal muscle fibres from frog and mouse: effects of extracellular lactate
Jan Lannergren, Joseph D. Bruton and Hakan Westerblad
Journal of Physiology (2000), 526.3, pp. 597Â—611 597
Stretch-activated ion channels contribute to membrane depolarization after eccentric contractions
Todd A. McBride, Bradley W. Stockert, Fredric A. Gorin, and Richard C. Carlsen
Appl. Physiol. 88: 91 Â– 101, 2000.
Uncoupling of in vivo torque production from EMG in mouse muscles injured by eccentric contractions
Gordon L. Warren, Christopher P. Ingalls, Shree J. Shah and R. B. Armstrong
Journal of Physiology (1999), 515.2, pp. 609Â—619
In isolated muscle fiber studies and animal models, non fatiguing eccentric protocols produced significant and extended force decrements over fatiguing isometric protocols. In many cases, force production in the isometric groups returned to pre-stimulus values within hours, even though the muscles were stimulated to the point where force production was no longer possible (complete short term fatigue). Whereas in the eccentric groups, force production did not reach pre-stimulus values for a much longer time interval (10-14 days). In the McBride et al study (2000) the lower repetition eccentric group experienced a longer force decrement (14 days) as compared to the higher eccentric repetition group (10 days). Although, this was likely due to the intensity (tension) and not necessarily the repetition number (greater tension requiring a lower repetition number).
Warren et al (1999) showed the following:
“Peak torque declined by 43% from the first to the last contraction in the ECC protocol, whereas peak torque did not change significantly during the CON protocol. Immediately after the ECC protocol, isometric torques were significantly decreased at all stimulation frequencies with the greatest relative deficits (i.e. 83Â—-89 %) occurring at stimulation frequencies â‰¤ 125 Hz (Fig. 3); at stimulation frequencies â‰¥ 250 Hz, the percentage decreases in isometric torque were 47-Â—49 %. In the 14 days following the ECC protocol, isometric torque showed a progressive recovery, but even at 14 days post-protocol, torques at all stimulation frequencies were lower than baseline levels by 12Â—-30 %. Immediately after the CON protocol, isometric torques measured at stimulation frequencies â‰¥ 250 Hz were increased by 5Â—-7% while torques at â‰¤ 100 Hz were decreased by 18Â—-25% (Fig. 3). Isometric torques measured at all stimulation frequencies were not different from baseline levels 1 day after the CON protocol and did not change until 14 days after the CON protocol. Fourteen days after the CON protocol, isometric torques measured at stimulation frequencies â‰¥ 125 Hz were significantly greater than baseline levels by 10Â—-11 %.”
Topical ReviewMuscle damage from eccentric exercise: mechanism, mechanical signs, adaptation and clinical applications
U. Proske and D. L. Morgan
Journal of Physiology(2001), 537.2, pp.333Â–-345
These studies demonstrate that the concept of “inroad” is flawed. We are dealing with two different physiological phenomena. The first is short term muscle fatigue / force decrement due to metabolic perturbations, substrate depletion, and possibly short term changes in the t-tubules. The second is long term force decrement resulting from damage to the contractile and non-contractile cytoskeletal proteins, plasma membrane, and longer term changes in the t-tubules (such as the formation of vacuoles) accompanied by other disruptions in the E-C coupling system distal to the neuromuscular junction.