Improving your athletic form

My husband and my iPhone did not agree about my running form. My husband, eyeing me critically as I ran back and forth in our backyard while he filmed me, told me that I needed to keep my head up and stop flailing my arms like Jerry Lewis in The Nutty Professor.

My new iPhone app told me that my running form was "superb."

This disagreement tells you a great deal about the state of today's most ambitious smartphone coaching apps, especially since one of those assessments was more accurate than the other, and it was not the one on my phone.

Many of us who participate in sports worry about our form. Good form is desirable, since it's generally accepted that someone with good form, which is also known as good technique, is likely to perform better at his or her chosen sport and be less prone to injury.

But improving your form isn't easy. Well-heeled athletes often employ a retinue of coaches and biomechanics consultants to regularly critique and fine-tune their form.

Most of us don't have such resources and, in the past, generally relied on advice from training partners or spouses. More recently, many of us have turned to simple smartphone apps that provide recorded videos or animations showing us what the app's developers consider to be good form for our sport, whether that sport happens to be tennis, golf, baseball, weight training, basketball, soccer, swimming, running or virtually any other activity.

But now a new generation of apps are going a step farther and providing a personalised assessment of form, together with suggestions for how to better it. These apps, with names like RunForm, BarSense, and Hudl Technique, generally require you to film yourself while you serve, squat, swing, throw, lift, run or otherwise work out.

You then upload that video to the app, and it allows you to view yourself in super slow motion, frame by frame, with accompanying commentary; overlay your swing or serve above that of a professional athlete performing the same move; or have the app use complicated geometry and algorithms to draw lines and circles across your body, assessing how you move, compared to an ideal version of that movement.

Essentially, it compares your golf swing, tennis serve or stride with a presumably perfect one and tells you how you've strayed from that model.

In general, these apps base their portrayals of good form on what the developers personally consider to be established coaching practices in the sport in question.

BarSense, for instance, an app aimed at weight trainers, mixes "judgment, experience, studies and just plain old physics" in its assessments of how users should be lifting and squatting, said Martin Drashkov, a software engineer and weight trainer who developed the app. (It is currently available only for Android phones.)

Similarly, the RunForm app was developed based on "hours of studying running technique," according to its website. The developers then determined idealised "ratios and spaces among different parts of the body and the surface you are running on," which, if adhered to, should yield better, faster strides.

In my case, RunForm, which is in beta release at the moment, drew a red bubble around my foot on one frame of my video and informed me that I land near the front of my foot, which earned me five stars from the app.

"First point of contact when landing should be your midfoot or forefoot," the accompanying text informed me.

My stride length was a bit less laudatory, the app felt, bordering on overstriding. "Avoid landing with your ankle in front of your knee," it wrote. But, over all, the app felt that my form was unimpeachable.

Unfortunately, from a scientific standpoint, the perfect form for almost any sporting technique remains elusive.

"The ideal biomechanics of a variety of human movements is a holy grail that may never be obtained," said Justin Keogh, a professor of exercise sciences at Bond University in Australia, who has extensively studied and written about skills learning and biomechanics in golf and other sports.

The problem with establishing one best way to move, Keogh said, is that if you look at successful professionals, many of them have very idiosyncratic techniques.

In golf, for instance, he said, "the most important aspect of biomechanics is that the club head must make contact with the ball in the exact way the player wishes contact to occur." Backswing, downswing and club head speed all must be in service of creating that perfect, desired meeting of club and ball, he said.

© 2015 The New York Times