Do I need to warm up?
Yes, and it takes five minutes: a few light sets of the lift you are about to do, not a stretching routine.
A warm-up does two things: it raises muscle temperature, and it lets you rehearse the movement with the weight you are about to use. Both are handled by the same approach, which is to do the lift itself with less weight.
For a working set of 100 kg, something like the empty bar, then 40, 60 and 80 kg for a few reps each. For running, five minutes easy before you pick up the pace. Save the long stretching for after, or for a separate session.
Compare
Sources
2
- Fradkin, A.J. et al. (2010). Effects of warming-up on physical performance: a systematic review with meta-analysis. J Strength Cond Res 24(1). 32 high quality studies: performance improved in 79% of the measures tested, and warming up rarely hurt.
- Behm, D.G. et al. (2016). Acute effects of muscle stretching on physical performance, range of motion, and injury incidence in healthy active individuals: a systematic review. Appl Physiol Nutr Metab 41(1). Long static holds before training cost a few percent of force; short holds followed by dynamic work do not.