I keep a regular workout routine, and due to living constraints I have tried to use bodyweight workouts as much as possible, with as little equipment as possible. So far I have been able to find exercises for almost every muscle group using no equipment, however I have not been able to find an equipment-free workout for biceps. Is there a bicep exercise I can do with absolutely no equipment (this includes bars, resistance bands and the like). Ideally I'd like something that I can do using only my body and a floor or wall if need be. Thanks!
There are also possible biceps workouts with a towel or rope: Towel biceps curls like: https://www.youtube.com/watch?v=Ir4lG8xKD1Q or http://www.healthylivingart.com/strength-training/home-grown-arms.html
or using a partner: http://kalimuscle.com/kalis-blog/biceps-curl-using-plastic-bag-or-towel/
Also, you could perform pullups on a door, which is essentially also minimal equipment :)
Due to the anatomy of the upper arm, I think you’ll need to concentrate on trying to perform exercises that allow you to “curl” your arm while also providing some level of resistance. With that in mind, you might consider:
Door way row with one arm.
Inverted rows with an underhand grip if you can adapt a table or some other structure to support your weight.
Front Double Biceps pose (Front flex) - while not a mass builder, is a form of isometric contraction that can help shape and define the arms. That’s why body builders spend countless hours practicing poses.
A useful resource when looking for targeted exercises is ExRx.net. It isn't comprehensive but it is close. It also shows the mechanics of many exercises which shows why you have a problem.
To work the biceps you need to be contracting the arm from the extended position to having your hands approach your shoulder. Without lifting objects or pulling your body towards a bar, I cannot imagine how to achieve this.
As mentioned above, "towel curls" are typically the go-to action, using items you have in your house. Similar exercises involve placing your hands on a fixed counter or bar and straining against the fixed object (although I would warn you to pick something firmly moored. It's surprisingly easy to uproot a kitchen counter or porch railing because they're built to resist forces from the other drections). Lastly, if you're allowing fixed objects, there's always the option of grabbing a fixed rail (or edge of a table), resting your heels on a smooth surface (such as a kitchen floor), and pulling your bodyweight back and forth under the area you're grabbing.
Theoretically, you could do isometrics, either providing resistance by flexing your triceps or by using your other hand to push down. I'm personally skeptical of isometrics, finding that they don't seem to have much positive exercise benefit, but I've known people who swear by them.