Final answer:
Marco should proceed to the next stage of increased workload in the YMCA Cycle protocol as his HR of 145 bpm is below the estimated maximum for his age, assuming no contraindications are present.
Step-by-step explanation:
Marco, a 22-year-old individual who weighs 185 pounds and is 5 feet 10.5 inches tall, has a resting heart rate (HR) of 56 bpm and finished his first stage of the YMCA Cycle protocol with an HR of 79 bpm. According to the exercise physiology, in healthy young individuals,
HR may increase to 150 bpm during exercise, and maximum HRs are normally in the range of 200-220 bpm, decreasing with age. Since Marco's HR after the second stage is 145 bpm, and assuming he is showing no signs of distress or exceeding his maximum HR (which can be estimated as 220 - age, giving 198 bpm for Marco), the protocol can typically be advanced to the next stage of increased workload, unless contraindications are present. In contrast, if Marco's HR were to approach his estimated maximum, it would be safer to end the test.