We calculate the average energy transfer and its straggling for a projectile colliding with inner shell electrons. The summation over allowed final states is performed explicitly, without using mean excitation energies or partial sum rules. We discuss the validity of the assumption of distant collisions and the dipole approximation, and apply them to the stopping power and straggling increase per unit path length for protons channeled in Si. A comparison is made with previous theoretical models and with experimental results, showing that the contribution obtained for inner shell electrons improves the agreement of the calculated stopping power with measured values over a wide range of collision velocities. It is also shown that the straggling due to inner shell electrons can be neglected.