Wire hang test

Muscle strength and neuromuscular function: Hanging bar

Ref.: Bellantuono I, de Cabo R, Ehninger D, Di Germanio C, Lawrie A, Miller J, Mitchell SJ, Navas-Enamorado I, Potter PK, Tchkonia T, Trejo JL, Lamming DW. A toolbox for the longitudinal assessment of healthspan in aging mice. Nat Protoc. 2020 Feb;15(2):540-574. doi: 10.1038/s41596-019-0256-1. Epub 2020 Jan 8. PMID: 31915391; PMCID: PMC7002283.

Hanging bar

· Hanging bar apparatus - A 50 cm wide, 2 mm thick metallic wire tightly secured between 2 vertical stands approximately 37-50 cm above a layer of bedding.

CRITICAL: Wire hang is also known as wire suspension latency test, wire hang, hang test or body suspension in the literature.

1. Acclimatize animals by placing them on the wire of the hanging bar apparatus for several minutes watching that they don’t use their back legs or tail to climb on the wire. Sometimes, the mice are difficult to position such that they use only the front limbs. This is a matter of patiently training the mice by gently repositioning it on the wire in the correct way until they learn. They may need to be repositioned several times because they tend to use only their hind limbs.

CRITICAL: In longitudinal studies young mice that have not been previously tested need to be trained and acclimatized by placing on the wire each day for 5 days. Old mice (24 months and older) usually are not so active, and do not jump on the wire or run on it, and thus can be trained only once prior to testing. The reliability of the results will depend on how well they are trained.

2. On the day of the test, bring all mice to the procedure room 30 min prior to the test to allow animals to acclimatize to local environmental cues.

3. Carefully take mouse at the base of its tail and bring it in proximity to the wire.

4. Let the mouse grasp the wire with the two forepaws only, and slowly lower the hind limbs in such a way that the mouse hangs on the wire only supported by its forepaws.

5. Start the timer as soon as the mouse is released.

6. When a mouse shows improper behavior (like balancing on or deliberately jumping off the wire, grabs the wire with four paws, or reaches the end of the wire) reposition the mouse on the wire without stopping the timer.

7. If mouse falls before 10 seconds have elapsed, remember what time they fell and quickly repeat the test. If on the 3rd try the mouse still falls before 10 seconds, record the best latency out of 3 attempts.

8. When a mouse falls off the wire, stop the timer and record the hanging time. When mice are able to hang for 5mins take them off the wire and return them to the cage.

9. Record hanging time.

10. Once one trial is completed for all the mice, complete a second trial by repeating steps 3-9. There should be an approximately 30 minutes break between trials for each mouse. Repeat steps 3-9 again so each mouse has done a total of 3 trials.

11. Take the best time out of the 3 trials for analysis and normalize results to lean mass or body weight or perform ANCOVA using weight or lean mass as covariant. In young mice and mice up to 18 months old, test every 6 months. After that, we recommend testing mice monthly.