Toe slide or flat? The biomechanics are clear: more than double the knee joint force on the toes. How to make and train that decision properly.
Sliding on the ball of the foot — the toe slide — produces more than double the knee joint force of sliding flat on the whole sole [1]. This is not a matter of taste and not a matter of style. It is the clearest number curling biomechanics has to say about your technique.
It was measured with in-shoe pressure sensors and video from the side: knee joint force correlates strongly with the moment arm of the ground reaction force — that is, how far in front of your knee your load sits [1]. The toe slide pushes hips and torso forward over the knee, the position becomes less stable, and the load rises [1].
Does that match what curlers actually feel? Almost exactly. In the only larger survey among competitive curlers, 79 per cent reported musculoskeletal complaints — knee 54 per cent, back 33, shoulder 20 — and the delivery was among the most frequent triggers [4]. Curling still counts as a relatively safe winter sport [4]; the problem is not the accident, it is the repetition.
Plain talk: what you decide here is not about looks, it is about the bill your knee pays over a season.
In the flatfoot slide the sliding foot lies on the ice with its whole sole, the ankle is flexed, the hips sit behind the knee. In the toe slide the foot rolls onto the ball, the sole tilts, the weight moves forward. Coaching treats flatfoot as the safe entry variant [5] — and the biomechanics supply the reason: more than double the knee joint force in the toe slide [1].
This is exactly where elite and sub-elite part ways: elite curlers show greater ankle dorsiflexion — more flexion, toes towards the shin — and therefore a larger contact area of the sliding foot on the ice; the moment of their centre of mass is positive, in sub-elite curlers negative [3]. More sole on the ice means more calm. Balance is trainable technique, not talent [3].
Film yourself from the side and look at a single line: are your hips behind or in front of the sliding leg's knee? The further in front, the longer the moment arm, the higher the knee joint force [1]. That one line is the whole difference — and it takes five seconds to judge in a still frame.
The delivery relies on coordinated activation for hip abduction, knee flexion and extension and external rotation, and the traditional technique markedly increases peak hip abduction, knee flexion and the associated joint moments [2]. In plain terms: abducting the hip carries the position. If your hip cannot do that, the knee takes over — and that is the road into the 54 per cent [4].
Not a ban, a bill. Anyone running the more aggressive variant needs targeted strength and stability training for hips and knees [2] plus honest volume management: fewer stones per session, more rest between blocks. And the slider then belongs at the thin end, not the fast one — thinner is slower and more stable [6].
Choose one variant, repeat it over weeks, do not jump according to daily form. Twenty draws per session, five of them on video, and the verdict comes from the still-frame line in step 3 — not from feel. Feel rewards precisely the position your knee punishes.
This is the one decision in curling for which a hard load figure exists — more than double the knee joint force in the toe slide [1] — and it does not act over one stone but over thousands. Anyone who already has knee problems settles the technique question with physiotherapy or sports medicine, not with an article.
Build the change progressively. A new slide variant loads hips and knees in an unfamiliar pattern [2]; three sessions at half volume are cheaper than six weeks off. And warm up before the first deep lunge.
The frame still holds: curling is a relatively safe winter sport, and the typical complaints are overuse, not trauma [4]. Which is exactly why the technique decision pays — overuse is the injury type you genuinely influence with technique. Even so, no guide replaces a coach's eye watching you live from the side.
Run the still-frame test over ten stones: side-on video, and on every stone freeze precisely the moment the stone reaches the near hog line. Draw a mental vertical through the sliding leg's knee and note only one thing: hips in front or behind?
Ten stones, ten yes-or-no answers. If you count "in front" five times, you do not have a balance problem, you have a technique decision you never consciously made — and by measurement that one costs you a factor of two at the knee [1].
For the vast majority of players: flat. In the toe slide the knee joint force is more than double that of flat sliding, and it rises with the moment arm of the ground reaction force [1]. Coaching therefore treats flatfoot as the safe variant [5]. Anyone running the toe slide needs targeted hip and knee strength work alongside it [2].
Usually too little sole on the ice. Elite curlers show more ankle dorsiflexion and therefore a larger contact area of the sliding foot; their centre of mass works with them rather than against them [3]. A thinner, slower slider also helps — 1/16 or 3/32 inch instead of competition material [6].
Because knees are the sport's most common complaint zone: 54 per cent of the competitive curlers surveyed reported knee problems, and the delivery was among the most frequent triggers [4]. The slide variant is the single biggest lever on that [1], hip strength the second [2].
Count in weeks, not sessions. The slide variant changes joint loading and muscle coordination across the whole delivery [2], so it belongs built up over several sessions at reduced volume. Track progress on the side-on video, not on feel [1][3].
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