The effects of intensified training in combination with a reduced training volume on muscle ion kinetics, transporters and work capacity were examined. Eight well-trained cyclists replaced their regular training with speed-endurance training (12x30-s sprints) 2-3 times per wk and aerobic high-intensity training (4-5x3-4min at 90-100% of maximal heart rate) 1-2 times per wk for 7 wks, and reduced training volume by 70% (intervention period; IP). The duration of an intense exhaustive cycling bout (EX2; 356±6 W), performed 2.5min after a 2-min intense cycle bout (EX1), was longer (p