I’ve been wondering about this since stuff like sled work involves resisting the friction generated by the ground and stuff like that.
It makes me wonder, would doing movements that involve some friction help to emphasize the concentric resistance and deemphasize the eccentric resistance? It wouldn’t be concentric-only but it seems like it would shift things in a favourable direction.
For example, for the elbow flexors, doing drag curls. The resistance from dragging the bar against your torso would make it harder to lift the weight (probably necessitating training with a lighter one) and similarly, on the way down, the friction would help to lessen the eccentric load your muscles need to take, almost like it was rolling down your body.
Another example is closed-door pull-ups, for people who have doorway mounted pull-up bars, their legs swing forward into the door and your thighs and knees rub against it on the way up and down. This makes it harder to lift up, but easier to lower down.
Another example is ab wheel rollouts against a high-friction surface, or for people who do those heavy barbell rollouts, they use heavy plates to generate more friciton too I think. The wheel does not roll out as easily due to the friction, requiring more relaxation of the lats and stuff to let it roll out, contracting more antagonist muscles for recipricol inhibition. Similarly, with higher friction it is harder to roll it in, maybe even giving a harder workout on your knees than on your toes with enough of it.
Another example might by say, pushing and pulling weights across a carpet while lying prone to use your upper and lower traps. The friction would make the muscles work harder in whatever direction they are going.
Another example would be something like lunges. Rather than the lunges where you lift the moving leg off the ground, you drag it along the ground generating some amount of friction, like those valslide things. That friction allows you to keep weight on the leg and decrease the muscular lowering work by the main working leg. The friction also resists getting back up into position. This seems valuable for stuff like stretching too since so much of strength stretching is eccentric or isometric contractions so the isometric contraction might be good if soreness is inhibiting people from stretching regularly.