Lunge with Bicep Curl
As you lunge forward with one leg, perform a bicep curl with the opposite arm. Bring arm to your side as you return to standing. Switch legs with each repetition.
Some general tips for lunging: keep the front knee in line with the ankle, try not to let your knee jut in front of the ankle or too much to either side, and put your weight into the front heel to propel yourself back to standing.