I got home last night and DH, who'd just had his chemo infusion late morning, was spinning on his home trainer with the chemo pump hanging off the handlebars
Exercising has been a huge help to him, both physically and mentally; just like you, he says that he feels better afterwards, even if it's sometimes really hard to get motivated to start (when he feels like crap and just laying in bed).
I know an oncologist in France who started his own "exercise club" for his cancer patients, after noticing over and over how much better people who exercised fared, both in terms of well-being during treatment and in terms of treatment efficacy.
Wife of Dx 04/18 (51 yo). MSS, KRAS G12A
No primary (involuted?)
Lytic tumor L4 vertebrae, EBRT 04/18, SBRT 02/19
Resect small intestine 05/18 (no cancer - Crohn's)
Failed adjuvant Xelox
Folfiri + Avastin 03/19 to 01/20
6.7 cm left adrenal mass 03/19, successful resection 02/20
CEA since 03/19: low 3.2, now 81.1
Scan 03/19: Multiple small lung nodules, now gone/calcified
PET 04/20 uptake by L4
L3-L4-L5 fusion surgery and partial corpectomy 05/20
Scan 06/17/2021: stable