A phrase thrown around so frequently, but to understand its relevance, you need an understanding of what is happening internally.
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Our body is made up of a system of pivots and levers. These are pulled and stabilised by various muscles in order to move us and various mass forms against the draws of gravity.
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Where the centre of the mass sits relative to the application of force (and vector of it) and the pivots being levered drastically affects the force required by the muscles internally in order to create movement.
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Muscles produce force.
Muscles grow to produce more force as an adaptation to the stimulus of being taken near their limits of being able to produce force.
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If the goal of your exercise is to move as much of a certain mass as possible through a set of rules then yes, you’re a powerlifter or crossfitter etc, and I guess progressive overload to you is all external. There’s nothing wrong with that, I salute and stand in awe of those capable of doing so with staggering amounts of weight through their hard work, consistency and beautiful segmental proportions + muscle insertions. Focus on external loads is sport though.
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If the goal is progressively increased internal force requirement from a muscle group, then we need progressively increased torque requirement at a joint. This MAY come from more mass, or, depending on how the increased mass affects the movement and resulting moment arm, it may not. Equally, the torque requirement can be manipulated, increased (and often improved, if we consider the accompanying joint strain) just by changing the influence of other joints or better aligning the intended muscle fibres... or THE RANGE moved through.
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Range is so much more than just range of external motion or even moment arms. It’s range of contractile lengths available to a muscle, that will almost always face increasing mechanical disadvantage past a certain point (think bone angle) - often drastically increasing the torque due to a reduced relevance of the internal force vector to the momentary direction of movement.
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Yes, it’s semantics. A ramble. Is it a relevant one? I don’t know - do you get paid to think about exercise at the highest level?
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