Mixed
Performing static hamstring stretching immediately before sets of the barbell back squat acutely increases biceps femoris muscle thickness without impairing total training volume or exercise performance.
If you want to target your hamstrings during squats, add a 40-second static hamstring stretch right before each squat set. Sit with legs extended, hinge forward until you feel a strong stretch (pain rating >7/10), hold for 40 seconds, then immediately perform your squat set. This will increase blood flow and muscle thickness in the hamstrings without hurting your performance or total volume.
Stretching the hamstrings immediately before each set of the back squat can be used to acutely increase biceps femoris thickness without impairing squat performance.
Why this rating
Randomized crossover design with resistance-trained subjects, but limited to acute effects (one session) and small sample size (n=14).
Source
Pre-stretching of the Hamstrings Before Squatting Acutely Increases Biceps Femoris Thickness Without Impairing Exercise Performance
Thiago Barbosa Trindade et al. · Frontiers in Physiology · 2020
This is one finding among thousands. Every one is graded and traced to its source, so you can see what the evidence actually supports. Browse the research →