The figure above is taken from a paper published recently in a physiology science journal. I will discuss the paper below. But I like to start with a teasing questions that gets to the core of the paper:
The figure shows a rowing cycle. Suppose that for some reason you want to include a 2 sec pause in the cycle. You have the choice to pause either at the finish position (A in fig.1) or at the catch position (C in fig.1), but the aim is to get the best possible performance (time or distance) under this particular choise. In other words: which pause has the lowest performance penalty? Please write down your choise and the argument(s) for it.
The paper is titled 10% Higher Rowing Power Outputs after Flexion-Extension-Cycle Compared to an Isolated Concentric Contraction in Sub-Elite Rowers published in Frontiers in Physiology, 2020. The authors are three German scientists in Physiology and Exercise Training. They have published more papers recently with intriguing titels, like Low intensity rowing with blood flow restriction over 5 weeks increases V̇O2max in elite rowers: A randomized controlled trial, in the Journal of Science and Medicine in Sport (2020). These papers are peer-reviewed, so this is not some frankencrank stuff.
The paper can be downloaded freely, but I didn't find it easy to read. One of the reasons is that I am not familiar with the distinction between concentric contraction and eccentric contraction of muscles. Only recently I have learned about Plyometrics. Plyometrics is a term for exercises that stretch and then shorten the muscle to accelerate the body or limb. It is a buzz word in physiology and in training. It often helps understanding by giving an example:
In 2-leg jumping there is the squat jump and the countermovement jump. In the squat jump (bottom sequence in figure below), the movement starts from a stationary squatted position. The countermovement jump (top sequence) starts from a upright position, going rapidly through the knees followed directly by a jump. It turns out the the coutermovement jump is more forceful, leading to a greater jump height and a longer time of flight. Differences of 18-20% have been shown. The explanation is that the leg muscles behave elastically for rapid movements. The sequence of an eccentric contraction (leg muscle rapidly stretched) followed directly by a shortening to accelerate the body upward, is called a stretch-shortening cycle. We perform such a stretch-shortening cycle in the transition from recovery (slide in the Fig. 1) to the drive. In another topic, I have argued that the rowing cycle has more similarity to a (horizontal) countermovement jump than to a deadlift.
You cannot find the answer to my teasing question directly in the paper. The authors compared three different isolated rowing drives starting from a complete standstill of the flywheel. This is certainly not the case after a 2 sec pause. But the essence, if I read the paper correctly, is that the motions of the slide (recovery) and the drive should be uninterrupted to conserve energy and optimize performance.
In fact this paper is also relevant for another long-standing question : is the kinetic energy built up in the recovery (½ m v²) completely lost at the catch or can it be used to some extend in the drive? The paper shows that in a rapid stretch-shortening cycle muscles behave as springs and can store energy.
I am very interested to hear the argument(s) for your choise.
