The goal of this clinical trial is to to compare the structure of the intestinal microbiome between children shortly after treatment for acute lymphoblastic leukemia (1-3 years after cancer treatment) and healthy controls. And then to provoke a positive shift of bacterial diversity by physical activity and probiotics in cured pediatric oncology patients with persistent gut microbiome disruptions.

The main question[s] it aims to answer are:

• Are differences in bacterial richness between healthy controls and pediatric oncology patients ≥12 months after cancer treatment apparent?
• Has the combination of physical exercise and probiotics had a positive influence on the structure of the gut microbiome in childhood cancer survivors in remission? Two times per week of physical activity and daily dairy consumption with probiotics will be required of participants for eight weeks.

Inclusion Criteria:

- children previously diagnosed and treated for acute lymphoblastic leukemia in remission between 1 and 3 years

Exclusion Criteria:

• acute respiratory infection during intervention
• more than 20% skipped exercise training sessions