Well, for players in a standing position, the weight of the arm just pulls the hand down toward the floor.
The truth is that in lower positions (closer to the nut), you can try to use the large muscles of your upper back and shoulder to pull the strig back against the fingerboard, but that's limited, otherwise the top of the thing waves around and if you persist the tip of the end pin will gradually skate away from you. In higher positions, the pull from those big muscles is countered by the upper bout of the bass against your abdomen, so using them makes perfect sense.
The key is not to "use no squeezing action" - if you draw a free body diagram of the forces involved in half position, you'll quickly see that's impossible - but to use ONLY as much force as you need and NO more. Yes, those big muscles will be engaged, but especially in low positions, so will be the thumb - but ONLY to the extent needed and NO more.
People always rabbit on about "play without tension" - but of course, if you played with ZERO tension, your knees would collapse, you'd fall to the floor, the bass would fall on the floor, breaking off the neck, and then where would you be? No, the correct formulation is "play with ONLY as much tension as needed and no more, and ONLY where you need it."
The fact that OP is finding himself holding his breath while playing is, right there, a clear indication that there's just way too much muscle tension in the whole body and in the whole way of addressing the bass.
My recommendation would be LONG TONES. Just focus on playing ONE NOTE, downbow, upbow, downbow, upbow, and experiment within yourself to find where you've got excess tension and where you're applying excessive force. Everything should feel "alert but relaxed", not tight. Shoulders, arms, back, fingers - just exert exactly the minimum force needed to prevent falling down or the bass falling down or dropping the bow.
The truth is that in lower positions (closer to the nut), you can try to use the large muscles of your upper back and shoulder to pull the strig back against the fingerboard, but that's limited, otherwise the top of the thing waves around and if you persist the tip of the end pin will gradually skate away from you. In higher positions, the pull from those big muscles is countered by the upper bout of the bass against your abdomen, so using them makes perfect sense.
The key is not to "use no squeezing action" - if you draw a free body diagram of the forces involved in half position, you'll quickly see that's impossible - but to use ONLY as much force as you need and NO more. Yes, those big muscles will be engaged, but especially in low positions, so will be the thumb - but ONLY to the extent needed and NO more.
People always rabbit on about "play without tension" - but of course, if you played with ZERO tension, your knees would collapse, you'd fall to the floor, the bass would fall on the floor, breaking off the neck, and then where would you be? No, the correct formulation is "play with ONLY as much tension as needed and no more, and ONLY where you need it."
The fact that OP is finding himself holding his breath while playing is, right there, a clear indication that there's just way too much muscle tension in the whole body and in the whole way of addressing the bass.
My recommendation would be LONG TONES. Just focus on playing ONE NOTE, downbow, upbow, downbow, upbow, and experiment within yourself to find where you've got excess tension and where you're applying excessive force. Everything should feel "alert but relaxed", not tight. Shoulders, arms, back, fingers - just exert exactly the minimum force needed to prevent falling down or the bass falling down or dropping the bow.
