Charlotte Kalla tested positive for covid-19 in November and has also suffered from back problems.
It has contributed to swaying results and she was questioned before the World Cup.
But the 33-year-old gave a message of strength in the World Cup skiathlon.
"I have been hot on small things"
Charlotte Kalla finished fifth in the race after a strong effort.
She lost fourth place in a sprint with Teresa Stadlober.
- It was great fun to compete.
I enjoyed having good skis in classic and skate, says Kalla to SVT Sport.
- It has felt good at the end.
I have been able to laugh at it, how I have heated up on small things.
I have been tagged and eager to get started.
Therese Johaug won World Cup gold.
Frida Karlsson took silver and Ebba Andersson got the bronze.
- They have felt incredibly strong and have been in a good mood since we left on the World Cup trip.
I had a feeling that they could go really fast today, says Kalla.
"So much fun"
- The World Cup has just started, it's so much fun that the dikes have met with the skis, and that we have met with the form.
Now she would like to run more races in the WC in Oberstdorf.
- I would like to continue competing during the World Cup.
Being this zone will lift me for every day.
I need to be here and be in pain, says Kalla.