Side and front cameras, three checkable markers and an honest limit: what a phone video reveals about your delivery — and what only instruments can.
Three features measurably separate elite from sub-elite curlers, and two of them are visible on a phone video: greater ankle dorsiflexion, a larger contact area of the sliding foot on the ice, and a positive rather than negative moment of the centre of mass [1]. Elite controls speed and balance in the delivery markedly better — and the mechanism behind it is banal enough to check in a still frame: more ankle flexion extends the toe joint further, the slider lies flatter, the slide gets calmer [1].
Just as important is the other half of this guide: what a video cannot do. The study on knee loading worked with in-shoe pressure distribution measurement plus sagittal video [3]; the work on muscle coordination in the delivery used kinetics and muscle activity [2]. Joint forces, moments and synergy patterns are not video quantities. Anyone reading them off a clip is hallucinating.
And the frame around it: curling research has been systematically reviewed — it exists, it is growing, and it is small [4]. There is no published norm table to compare your angle against. What exists are directions. So you work with directions — and with yourself as the reference.
From the side you see ankle angle, back line and the position of the hips relative to the knee. That is exactly the plane used alongside pressure measurement in the knee-loading study [3]. Set the camera at slider height, roughly level with the near hog line, and leave it there — identical week after week.
Freeze the frame once the slide is stable. Does the top of the foot pull towards the shin, or is the ankle stiff? Greater dorsiflexion is one of the two elite markers [1]. You are not measuring a degree value against a norm here — you are comparing today's still frame with your best of the last few weeks.
The second elite marker, derived directly from the first: a larger contact area of the sliding foot on the ice [1]. In the side-on video you spot it in the sole line — is it flat, or is it tipping onto the ball or the outer edge? Flat is calm. Tipping is a correction still to come.
In the still frame, draw a vertical through the sliding leg's knee. If the hips sit in front of it, the moment arm of the ground reaction force gets longer — and knee joint force correlates strongly with exactly that [3]. In the toe slide it is more than double that of flat sliding [3]. At the same time check that the back stays long: back loading arises above all from a back that is not straight in the deep position and in the delivery [6].
From the front you see what the side conceals: hip abduction and whether shoulder and pelvic axes point at the skip's broom. The delivery relies on coordinated activation for hip abduction, knee flexion and extension and external rotation [2] — whether that chain is cleanly aligned is visible front-on, not sagittally.
A clip without a time is an opinion. Note the hog-to-hog time for every video; a draw typically runs 13.0 to 14.5 seconds, and 0.1 seconds of difference equals about six feet of running distance [5]. That is how you separate technique errors from weight errors — otherwise you discuss both at once and solve neither.
Video analysis tempts you into technique experiments under fatigue, because you want it "clean one more time". That is exactly when risk rises: the traditional delivery technique markedly increases peak hip abduction, knee flexion and the associated joint moments [2], and in the toe slide knee joint force is more than doubled [3]. Ten analysis stones are enough; the eleventh is statistics without benefit.
Watch the back line explicitly in the video, not just the legs. Back loading arises above all from a back that is not straight in the deep lunge and in the delivery [6] — and that error is instantly visible in a still frame while being practically invisible from the inside.
And the honest limit: video self-assessment replaces neither coaching, nor performance testing, nor medical assessment. It gives you observations — the judgment belongs to experienced eyes.
Build yourself a three-tick card: for each of the ten stones you make three ticks or crosses — dorsiflexion visible (yes/no), sole flat (yes/no), hips behind the knee (yes/no) [1][3]. No angles, no grades, just three binary answers.
After ten stones you have a number between 0 and 30. After four sessions you have a curve. And the curve answers the only question that matters: do the three features survive when you get tired? If they fall apart from stone seven onwards, your problem is not technique but endurance in the position — and you train that somewhere else.
Mainly three: ankle dorsiflexion, the contact area of the sliding foot and the position of the hips relative to the knee [1][3]. The first two are the published markers separating elite from sub-elite [1]. Not assessable are joint forces, moments and muscle activation — those need instrumentation [2][3].
Main camera side-on at slider height, roughly level with the near hog line — the plane in which knee loading was also studied [3]. Second camera front-on behind the house for hip abduction and alignment [2]. Both positions stay identical across weeks, otherwise no comparison is possible.
Usually too little sole contact. Elite curlers show greater dorsiflexion and therefore a larger contact area of the sliding foot; their centre-of-mass moment is positive, in sub-elite curlers negative [1]. In the side-on video you see it in the sole line — flat or on the edge.
No. Curling research has been systematically reviewed and remains small [4]; what is published are directional findings such as "elite shows more dorsiflexion and more contact area" [1], not norm tables for recreational players. Your reference is your own best still frame — plus the hog-to-hog time as an objective second channel [5].
Sweeping at Performance Level: Force, Frequency, Ice Friction and the Physics of the Last Centimetre