Changes in strength performance of highly trained athletes after COVID-19, 2024, Jie Caio et al

[Mij]

Abstract
Introduction
This study aimed to explore the impact of COVID-19 on strength performance in highly trained athletes.

Method
A force plate was employed to measure squat jump height (SJH), counter-movement jump height (CMJH), and drop jump reactive strength index (DJRSI) in 27 highly trained athletes before infection, and at one week, two weeks, and four weeks post-recovery. Additionally, an Isometric Mid-thigh Pull (IMTP) test was conducted to record maximum isometric strength (MIS) and the rate of force development of the initial phase (RFD 0–50; RFD 0–100). Repeated measures analysis of variance was utilized to compare variations in these indicators across different time points.

Results
One week post-recovery, SJH (-7.71%, P = 0.005), CMJH (-9.08%, P < 0.001), DJRSI (-28.88%, P < 0.001), MIS (-18.95%, P < 0.001), RFD 0–50 (-64.98%, P < 0.001), and RFD 0–100 (-53.65%, P < 0.001) were significantly lower than pre-infection levels. Four weeks post-recovery, SJH (-2.08%, P = 0.236), CMJH (-3.28%, P = 0.277), and MIS (-3.32%, P = 0.174) did not differ significantly from pre-infection levels. However, DJRSI (-11.24%, P = 0.013), RFD 0–50 (-31.37%, P = 0.002), and RFD 0–100 (-18.99%, P = 0.001) remained significantly lower than pre-infection levels.

Conclusion
After COVID-19, highly trained athletes exhibited a significant reduction in maximum strength, explosive strength, reactive strength, and initial phase force generation capability. By four weeks post-recovery, their maximum and explosive strength had returned to near pre-infection levels, yet their reactive strength and initial phase force generation capability remained significantly impaired.
LINK

 

[Sean]

...yet their reactive strength and initial phase force generation capability remained significantly impaired.

That is interesting.

 

[bobbler]

That is interesting.

it is interesting because that reactive is about absorbing the prior movement then initiating the next. I can almost see the overlap to the 2 day CPET vs the one day one. On the basis of it being about recovery for repetition - in the athletic sense rather than the illness sense.

But I guess also somewhat about that illness form, because between 1-4wks after infection the other forms did recover to pre-infection levels, we just don't know whether this one takes longer (because they didn't test beyond 4 weeks) or ever returns to what it is in all. And then of course at that point it mightn't be about averages if it is just one or two who have lingering but significant effects and others not.

When I read this abstract one question I thought I needed to look up when feeling up to it was what order the tasks were being done in. Because if the ones that weren't improving always happened to be at the end of the battery then it could have other factors than just the difference between the individual tasks involved of course.

 

[bobbler]

That is interesting.

If it turns out it is a repeatable finding... I've been trying to look up particularly the second of the two and ended up coming across the following, I've no idea whether I'm going a bit off-piste


Force Generation - an overview | ScienceDirect Topics scroll to the bottom of this page - it is the last one, I would have clicked through to the abstract and posted that link but it isn't the same thing that is on this page which has a much longer amount of text. Seems worth a read. It's from
Internal force generation
Andrew Horwood, Nachiappan Chockalingam, in Clinical Biomechanics in Human Locomotion, 2023


Here is one quote:

Active force generation involves metabolism for energy-producing movements of the myofilaments along one another through actin–myosin cross-bridge cycles. Passive forces are generated by the structural mechanical properties of the muscle fibres and associated connective tissue under tension and do not involve energy production through metabolism. Passive forces operate mostly near to a sarcomere’s maximum fibre length. Both muscle cellular wall collagen and internal cellular titin play fundamental roles in passive force, with titin playing the larger part in normal ranges of motion. Titin, through its linkage to actin and myosin, is also involved in active force generation.