On average Men age 17-25 should burn around 143 calories in a 20 minute period and Men 25-35 a theoretical 129 calories over 20 minutes. Women in the 17-21 age range, on average burn 136 calories with Women 25-35 burning 122.
Over 35s Men over 35 should burn around 114 calories in a 20 minutes period and Women over 35 around 109 over 20 minutes.
Over 60s Men over 60 should burn 100 calories in 20 minutes with Women over 60 burning 95.
What is Average? Everyone is different. More accuracy can be found by referring to your weight below. Calorie burn generally declines as we get older but not always. People who stay active will often keep the higher burn rate as they age.
Calories Burned based on Time and Weight.
Calories Burned in 15 minutes

Weight 100lb:71
Weight 120lb:86
Weight 125lb:89
Weight 150lb:107
Weight 175lb:125
Weight 200lb:143
Weight 250lb:179
Weight 300lb:214
Calories Burned in 40 minutes

Weight 100lb:191
Weight 120lb:229
Weight 125lb:238
Weight 150lb:286
Weight 175lb:333
Weight 200lb:381
Weight 250lb:476
Weight 300lb:572
Calories Burned in 45 minutes

Weight 100lb:214
Weight 120lb:257
Weight 125lb:268
Weight 150lb:321
Weight 175lb:375
Weight 200lb:429
Weight 250lb:536
Weight 300lb:643
Calories Burned in 1 hour 15 mins

Weight 100lb:357
Weight 120lb:429
Weight 125lb:447
Weight 150lb:536
Weight 175lb:625
Weight 200lb:714
Weight 250lb:893
Weight 300lb:1072
Calories Burned in 1 hour 30 mins

Weight 100lb:429
Weight 120lb:514
Weight 125lb:536
Weight 150lb:643
Weight 175lb:750
Weight 200lb:857
Weight 250lb:1072
Weight 300lb:1286
Calories Burned in 2 hours

Weight 100lb:572
Weight 120lb:686
Weight 125lb:714
Weight 150lb:857
Weight 175lb:1000
Weight 200lb:1143
Weight 250lb:1429
Weight 300lb:1715