Drive the pad down by pushing your heels into it; don’t just aim for 90*, get it right back. Imagine you’re trying to kick yourself under the seat.
The benefits are in the negative phase on this lift, so resist the urge to let the weight pop up. Instead, control it and raise it slowly to the start position.
TIP: This machine won’t allow as much range of motion as a Lying Leg Curl, but this means you’ll likely be able to lift more weight here. Also, you’ll be able to perform this movement without stretching your calves (common issue on the lying variation).