I don't think this is saying 1 minute of high-intensity sprints is better than all other exercise, if you're doing multiple 40+ km bike rides per week you're pr

I don't think this is saying 1 minute of high-intensity sprints is better than all other exercise, if you're doing multiple 40+ km bike rides per week you're probably not the intended audience for this type of exercise. However, I do think it is fair to use the word "fitness" as short-hand for what they were measuring because the below (from the "Results" in the Abstract linked) is a bit of a mouthful and doesn't neatly fit in the title: " Peak oxygen uptake increased after training by 19% in both groups (SIT: 32±7 to 38±8; MICT: 34±6 to 40±8ml/kg/min; p<0.001 for both). Insulin sensitivity index (CSI), determined by intravenous glucose tolerance tests performed before and 72 hours after training, increased similarly after SIT (4.9±2.5 to 7.5±4.7, p = 0.002) and MICT (5.0±3.3 to 6.7±5.0 x 10-4 min-1 [μU/mL]-1, p = 0.013) (p<0.05). Skeletal muscle mitochondrial content also increased similarly after SIT and MICT, as primarily reflected by the maximal activity of citrate synthase (CS; P<0.001). The corresponding changes in the control group were small for VO2peak (p = 0.99), CSI (p = 0.63) and CS (p = 0.97). "