For sport coaches reference and only an n=1, so please take it for what it is.
An athlete I’m working with had a great 6 weeks of racing from the start of Jan until mid-Feb, culminating in lifetime legal PBs of 10.47 (+1.5), 29-Jan, and 21.17 (-0.6), 15-Jan, plus some fantastic performances in the Adelaide Track Classic Tour Meet (see below) on Feb 12th.
Unfortunately, he and his partner, who I also coach, tested positive for COVID-19 on the 18th of Feb, which hit them pretty hard and due to local South Australian laws, were to isolate 10 days. After the initial nauseous and lethargy, they attempted to do some training with what they had, i.ie bike intervals, gym sessions etc, until they could leave the house. He started training again on the 28th of Feb and I could see he had lost a step or two, plus visually appears to have lost muscle mass. With Nationals at the end of the month, he needed to start racing again so ran a 200m on the 12th of March, 21.44 (0.0), really battling to the line for the final 50m, and then today on the 19th of March ran a 100m in 10.66, -0.4. All in all they are not back results but still very frustrating considering we thought he was on the verge of running sub 21 in the 200 and potentially pushing his 100 down into the low 10.4s. This trend after COVID-19 also occurred with another athlete who runs 200/400 we are close with, showing the impact the virus has on the physiological and neuromuscular systems, at least in the short term. Several distance coaches contacted me after I posted on Twitter, stating that many of their athletes shut their season down early as the performance implications were too much to overcome before Nationals.