I went to an interesting musculoskeletal research retreat recently (I had to give an invited talk, though – no such thing as a free lunch). As an added bonus it also informed my IS practise. So bear with me as I make a short story long.
The insights came during a talk on investigating tendon strain, which in the achilles is a significant health issue. A multi-national group had examined various protocols for healing the achilles tendon (see reference at end). The work kept tendons, sourced from rabbit cadavers, in an artificial environment for a prolonged period of time. Rabbit tendons are very similar to human ones and easier to source. The tendons were stretched at varying levels of strain for different time periods using a set protocol and the resultant strength measured over time. The work ultimately is to assess what might be best practice in recovery protocols.
It turns out there is a sweet spot at 6% strain ( under 0.25 Hz – a 4 second cycle of 1s graded strain, 1s hold, 1s reduction and 1s release). Any less strain and there is natural decay, any more strain damages the tendon – interesting news for us IS try-hards. The cycle time was chosen from previous rabbit treadmill studies that varied the step rate ( loading time) and looked at tendon strength after. In humans and possibly related (though its muscle) we know from other researchers that oxygen depletion in humans takes place in the muscles inducing the strain after 6–7 seconds (see 2nd ref below) so its all in the same ball park.
From science to inferences for IS training:
If we consider similarities between tendon and fascia, this provides good evidence (or indication at least) of how much muscle to use, how hard to try and for how long in exercises that seek to build conditioning eg winding, reeling, bowing, balloon man, skin breathing, opening and closing qua,10 of 10 and so on. Many of these traditional methods talk about not forcing, working with intention and have cyclic periods of strain and relaxing. 6% is then something of a middle ground, where there would be good reasons to go a bit higher, perhaps to weed out the connections not wanted or for elongation. Cycle time too might be something to do with the art it is embedded in, to build coordination ( eg bowing) or historical ( eg the shinto rites of spring)
So how much is 6% strain? Good question. Neglecting the complexity of dynamic and static strain, it’s possible to get into the ball park, I think, and discover how we might be trying too hard.
By putting the tips of your two index fingers together and pushing so they bend back until there is the onset of pain. Let’s call this 50% strain. (It’s a stab in the dark but a reasonable assumption – choose a different number if you want.) Try again and only push half as hard for 25%. Reduce the effort by half for 12.5% and repaet and half that for 6.25%. Its not very much by the time you get to 6%, maybe this is the illusive intention for those of us struggling with whatnthat might mean.
You can also try to find 6% strain with this method on an IS exercise of your choice if you think it’s relevant.
Understanding 6% or intention benefits other IS exercises that aim to recruit deep rather than surface muscles. For example, opening the hips (or that component of the qua), where applying too much effort tends to recruit superficial muscles. You can explore this by placing your hands on your buttocks or glutes (or other muscle of choice) to ensure they remain relaxed as you practise. Using only 6% strain in opening the hips should ensure only deep muscles are engaged (with practise), whereas using more effort engages superficial muscles and is potentially counterproductive.
Anyway, the ideas above move from a reasonable scientific foundation to inference and conjecture by a relative IS neophyte. Please take what’s helpful if any and let me know about the rest. I would be grateful for your thoughts and comments to inform my personal practice.
Many thanks to Andrew, Mike and Aran for feedback in the writing
Find then on google scholar, you may need an .edu.x domain to download for free though
Programmable mechanical stimulation influences tendon homeostasis in a bioreactor system
Tao Wang1, Zhen Lin1,2, Robert E. Day3,Bruce Gardiner4, Euphemie Landao-Bassonga1, Jonas Rubenson5, Thomas B. Kirk6, David W. Smith4, David G. Lloyd7,Gerard Hardisty8, Allan Wang9, Qiujian Zheng2 andMing H. Zheng1,*
Article first published online: 4 FEB 2013, DOI: 10.1002/bit.24809, Copyright © 2012 Wiley Periodicals, Inc.
Biotechnology and Bioengineering
Volume 110, Issue 5, pages 1495–1507, May 2013
Identification of functional programmable mechanical stimulation (PMS) on tendon not only provides the insight of the tendon homeostasis under physical/pathological condition, but also guides a better engineering strategy for tendon regeneration. The aims of the study are to design a bioreactor system with PMS to mimic the in vivo loading conditions, and to define the impact of different cyclic tensile strain on tendon. Rabbit Achilles tendons were loaded in the bioreactor with/without cyclic tensile loading (0.25 Hz for 8 h/day, 0–9% for 6 days). Tendons without loading lost its structure integrity as evidenced by disorientated collagen fiber, increased type III collagen expression, and increased cell apoptosis. Tendons with 3% of cyclic tensile loading had moderate matrix deterioration and elevated expression levels of MMP-1, 3, and 12, whilst exceeded loading regime of 9% caused massive rupture of collagen bundle. However, 6% of cyclic tensile strain was able to maintain the structural integrity and cellular function. Our data indicated that an optimal PMS is required to maintain the tendon homeostasis and there is only a narrow range of tensile strain that can induce the anabolic action. The clinical impact of this study is that optimized eccentric training program is needed to achieve maximum beneficial effects on chronic tendinopathy management. Biotechnol. Bioeng. 2013; 110: 1495–1507. © 2012 Wiley Periodicals, Inc.
Lumbar erector spinae oxygenation during prolonged contractions: implications for prolonged work
SM McGill, RL Hughson, K Parks – Ergonomics, 2000 – Taylor & Francis
… HICKS, A., MCGILL, SM and HUGHSON, R. 1999, Forearm muscle blood ¯ ow and … and magnitude of blood ¯ow changes in the human quadriceps muscles following isometric …LANOCE, V. and CHANCE, B. 1989, Noninvasive detection of skeletal muscle underperfusion with …