John Power: I am 6ft, 12 1/2st, 40 years old. I run and concept row regularly and would consider myself reasonably fit (p.b.t's rower 2000 <8min 5000 <21min). I would like to use the concept for muscle/weight gain and whereas I assume this will entail sprints at high settings I can find no guide to base this sort of exercise on. Also I have a heart monitor and find that if I stay within the heart rate recommendations for my age I do not feel as if I have had a good work out. Perhaps you could advise?Terry O'Neill: To be honest the Indoor Rower is not the most efficient way to increase muscle mass. To increase muscle mass you need to train in the region of 85-90% of your maximum muscle strength. The Indoor Rower develops power and endurance and, by varying the training, you can bias towards the power end or the endurance end. If you check out the Concept 2 Training Guide [http://www.therowingcompany.com/v4/training_prog.htm] you'll find some exercises to develop power in the section on training for a marathon. In order to better deal with the question of muscle and weight gain, we are in the process of developing the Concept 2 DYNO. This provides dynamic strength training on the leg press, bench press and bench pull all on the one machine that is no bigger than a rower. It works on the same principle as the rower in that the resistance is air but it has a wide load range of up to 1000lbs. A few months on this machine and you'll have muscles on your muscles. The DYNO will be released at the end of February.As far as the heart rate training is concerned the figures in the guide are ballpark and will err on the safe side. You can determine your own max. heart rate on the machine by simply thoroughly warming up and then row 45sec. absolutely flat out pulling as hard as you can. You may find your heart rate will continue to rise after you actually finish the 45sec. but the highest you will see will be near enough your max.