Figure 1.

Light micrograph showing a mouse tibialis anterior (TA) muscle prepared for second harmonic generation (SHG) imaging of in vivo sarcomeres. A small portion of the implanted tendon force transducer can be seen at the distal end. The mid-belly of the TA, marked by the red circle, displaced ~375 μm proximally when going from the relaxed (A) to the activated (B) state. Two fluorescent markers that were separated by 1 mm were applied at the mid-belly of the TA (in proximity to the red circle) and observed under fluorescent light to measure the local displacement of the muscle caused by activation.