Collision detection for individual objects(sensors) in LibGDX, box3d java game

I'm currently developing an Endless Runner in LibGDX. I have 4 sensors (upper-far, upper-close, lower-far, lower-close, will be used for machine learning later). I need to detect collisions between each sensor and object called Enemy. Right now it detects collisions between object of type Sensor and Enemy and that's correct but I don't know which individual Sensor is actually triggered. Here's the code responsible for collision detecting (in GameStage method):

@Override
public void beginContact(Contact contact) {

    Body a = contact.getFixtureA().getBody();
    Body b = contact.getFixtureB().getBody();

    if ((BodyUtils.bodyIsRunner(a) && BodyUtils.bodyIsEnemy(b)) ||
            (BodyUtils.bodyIsEnemy(a) && BodyUtils.bodyIsRunner(b))) {
        runner.hit();
    }else if ((BodyUtils.bodyIsEnemy(a) && BodyUtils.bodyIsSensor(b)) ||
            (BodyUtils.bodyIsSensor(a) && BodyUtils.bodyIsEnemy(b))) {

    } else if ((BodyUtils.bodyIsRunner(a) && BodyUtils.bodyIsGround(b)) ||
    (BodyUtils.bodyIsGround(a) && BodyUtils.bodyIsRunner(b))) {
        runner.landed();
    }
}

BodyUtils: public class BodyUtils {

public static boolean bodyInBounds(Body body) {
    UserData userData = (UserData) body.getUserData();

    switch (userData.getUserDataType()) {
        case RUNNER:
        case ENEMY:
            return body.getPosition().x + userData.getWidth() / 2 > 0;
    }

    return true;
}

public static boolean bodyIsEnemy(Body body) {
    UserData userData = (UserData) body.getUserData();

    return userData != null && userData.getUserDataType() == UserDataType.ENEMY;
}

public static boolean bodyIsRunner(Body body) {
    UserData userData = (UserData) body.getUserData();

    return userData != null && userData.getUserDataType() == UserDataType.RUNNER;
}

public static boolean bodyIsGround(Body body) {
    UserData userData = (UserData) body.getUserData();

    return userData != null && userData.getUserDataType() == UserDataType.GROUND;
}

public static boolean bodyIsSensor(Body body) {
    UserData userData = (UserData) body.getUserData();
    return userData != null && userData.getUserDataType() == UserDataType.SENSOR;
}

}

and here is the whole code (most important part about userData in box2 package): https://github.com/SzymonGalazka/Machine-Learning-Runner/tree/master/core/src/com/pl/runner