Can anybody help me to find out why high frequency fatigue (100 Hz stimulation of plantar flexors) is greater than low frequency fatigue (20Hz) during 2-min isometric load, after whole body cooling in 14 °C water (muscle temperature decreases about 6 °C), if comparing to control conditions?
Simply speaking each and every thing on earth has natural frequencies and the response is maximized (resonance) if the load is applied at a frequency equal to one of the natural frequencies. Hence, you need to know the natural frequency first in order to know whether the response is a resonant response or not.
If it is at constant amplitude then the high frequency is a lot more damaging - what is the amplitude - usually the higher the freq the lower the amplitude
Thank you for answers, but I need more scientific evidence. For example: Benton et al. [5] and Jones et al. [31] demonstrated that electrical stimulation (ES) at a frequency below 40–50 Hz solicited more and more Type I, slow-twitch muscle fibers that are more resistant to muscle fatigue, when higher frequencies (HF) solicited more Type IIa and IIb fast-twitch muscle fibers that are easily fatigued. It's possible that HF stimulus involve more fast-twitch fibers, but what happens with it after cold exposure in molecular level if HF fatigue is greater then in control exercise?
You should search the answer in neurophysiological background of cryotherapy. Following studies should help you. The second may invoke the idea, that coolong has similar effect as the fatigue (decrease in nerve conduction velocity), so you may search for studies with spectral density indiciators of cryotherapy effects
Kimura, I. F., Thompson, G. T., & Gulick, D. T. (1997). The effect of cryotherapy on eccentric plantar flexion peak torque and endurance. Journal of athletic training, 32(2), 124.
Algafly, A. A., & George, K. P. (2007). The effect of cryotherapy on nerve conduction velocity, pain threshold and pain tolerance. British journal of sports medicine, 41(6), 365-369.