Joined: Oct 2018
Posts: 2,182
Likes: 1,055
From: Columbus, OH
Bikes: Pake C'Mute Touring/Commuter Build, 1989 Kona Cinder Cone, 1995 Trek 5200, 1973 Raleigh Super Course FG, 1969 Raleigh Superbe, 1986 Miyata Nine : 1960/61 Montgomery Ward Hawthorne "thrift" 3 speed, by Hercules (sold), 1966 Schwinn Deluxe Racer (sold)
The hip sled isolates your quads and glutes from the minor groups that contribute to functional strength. You're right that the 45° angle reduces the total weight you're actually moving. Ballpark suggests that it's greater than 50% of the weight, but less than actually squatting 300. It's probably complicated since you need to figure friction, but it's solvable with vectors and trig.