All of human movement can be broadly classified into six categories: pulling, pushing, squatting, hinging, lunging and carrying. Of all these, the hinge is the one pattern that people tend to exhibit faulty movement the most. While we all know about the difference between bending at the waist and at the hip, it is the knee that is next in line for being the culprit behind horrible hinges.
A common mistake is for people to keep their knees locked while hingeing. They’re not completely extended; an example of this would be someone hinging with absoultely zero knee flexion altogether. While the resulting stretch you feel in your hamstrings may convince you that you’re nailing te beejezus out of your hip hinge, the truth is that you’re compromising your hip complex and shortchanging your ability to hinge properly.
This isn’t exactly all that surprising: functional fitness has done a heck of a job hammering home the difference between a hinge and a squat, so much so that an inexperienced individual tends to associate any amount of knee flexion with squatting. The truth is that a certain amount of knee flexion is required for the hip to properly hinge.
Restricting knee movement in the hinge automatically limits your range of motion as well as strength (think of the time your knees reached full extension before your hips during a deadlift). Force feeding this pattern often results in some compensation in the lumbar spine, which puts it at risk of being injured when subjected to moderate and heavy loads.
A slightly bent knee allows the glutes to lengthen and contribute to the movement. If you’re doing any variation of the deadlift, you should be able to feel your glutes working furiously, especially during the eccentric portion. In fact, a high volume deadlift workout should leave you feeling a pump in your glutes more than anywhere else!
So how much knee flexion is appropriate in a hinge? The exact amount differs between individuals on account of variances in hamstring length. However, a good cue to keep in mind is for the shins to remain completely vertical. A shin angle that is obtuse can be indicative of a hyperextended knee, while an acute angle means that the knees are travelling too far forward (unless you starting your pull from the ground with your hips low; some forward knee travel is to be expected then.). Think “soft knees” as you hinge. Don’t fight to keep them staight, but allow them to bend naturally without losing tension in the hamstrings.
My favourite method for practising this proper sequence is the single-leg Romanian deadlift (SLRDL). Starting out slow with just bodyweight allows you to focus squarely on positioning while building unilateral stability. If balance is an issue however, a regular bodyweight Romanian deadlift will do just fine. You can gradually progress to doing SLRDLs with weights to build strength and confidence. Master this and watch your health and performance grow (along with your backside)!