Ask FitnessMash

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Q. I have worked out regularly for several years and know the importance of warming up before my lifting session. I usually do about 10 minutes of light jogging or biking to elevate my heart rate and get the blood flowing, but I’m not sure this is correct. I hear the terms “dynamic warm-up” and “activation” tossed around a lot lately, but I don’t really know what they mean. Should I be warming up differently before I lift? – Alice Crowley, London, England

A. Good question, Alice. You are right in that you should warm up to increase circulation, but there’s a lot more to it than that. Properly preparing your body for a workout also involves taking your joints through a full range motion and waking up your central nervous system. A dynamic warm-up is a better choice than low-intensity cardio because it gets blood to the working muscles while also enhancing the movement quality of your subsequent lifts by improving mobility and motor patterns beforehand. For example, if your primary lift for the day is a squat, your warm-up might include leg swings (to increase mobility in the hip and allow for greater depth) and bodyweight squats (to wake up the CNS and groove the movement pattern before adding load). Activation is simply a technique used during a dynamic warm-up to “turn on” certain muscles so that they fire appropriately. In keeping with the squat example, you might include a set of hip bridges in your warm-up to activate your glutes so that you use them properly when you squat. Hope this helps!

Q. A trainer recently told me I should stop doing crunches because they are bad for the low back. I’ve heard this before, but is it actually true? - Andrew James, Los Angeles, CA

A. Unfortunately, Andrew, it is. The problem, however, lies not with the exercise itself, but with the issue of lumbar flexion. Low back specialist Dr. Stuart McGill has shown through his laboratory research that a sit-up places approximately 3500 Newtons (386 lbs.) of pressure on the lumbar spine, and that repeated cycles of lumbar flexion and extension cause damage to intervertebral discs. Over time, the disc breaks down until you have a full blown herniation. The act of crunching also shortens the rectus abdominis and reinforces bad posture, while EMG studies show more muscle activation occurs with core stabilization exercises than crunches anyway. So, why not get the most bang for your buck while minimizing risk?