Read the passage carefully and answer questions strictly as per the passage below:

In a space flight emergency, maximal explosive power may be critical for survival. Antonutto and coworkers measured maximal explosive power (single maximal contractions with both legs) with a dynamometer after as long as 180 days of flight. The maximal explosive power was reduced by 30% after 1 month and by 45% after 6 months.

In the Skylab program, as the duration of each mission increased from 28 to 56 to 84 days, in-flight exercise was increased from 30 to 60 to 90 min/day, respectively. Submaximal cycle exercise tests were performed before flight, every 5 to 6 days during flight and 2 days after flight. When the in-flight exercise responses were maintained, exercise responses after flight (including decreased cardiac output, stroke volume, and oxygen pulse, and elevated heart rate and ventilation) significantly decreased. The decrement after flight did not worsen with increasing flight duration, which led the investigators to conclude that the inflight exercise was useful for shortening the recovery period after flight.

The effects of in-flight dynamic exercise during shuttle missions on improving exercise responses after flight was evaluated on 30 shuttle crew members who performed various levels of in-flight exercise. The investigators evaluated exercise responses after flight by measuring the change in heart rate during a graded cycle exercise test. Even moderate volumes of in-flight dynamic exercise (cycle or treadmill exercise performed three times per week for 20 minutes per session) reduced the exercise heart rate response after flight.

Q) Even moderate volumes of which exercise reduced the exercise heart rate response after flight?