Decided to split this post off as a new thread. It was originally intended to be a reply to another where there was discussion about how hard it is to tread water for 10min, whether some people are inately negatively buoyant, etc. My position in that thread was two-fold:
After my morning swim of 3,000m (so I was good and tired) I swam out to the deep end and tried to float. Laying on my back with a normal, full breath my feet sank under me. As I settled in to a vertical position I was able to float with my head tilted back so that my chin, mouth, nose, and ears were out of the water. By controlling my breathing I was able to float this way for 10min without any sculling/kicking at all - arms crossed at my chest, legs crossed at my ankles. This was at 6am this morning. I could easily still be there floating motionless now if I wanted to be.
Next I tried to manage keeping my head above water in this same position with my lungs empty. I wanted to see how much effort was required to make up for not having the benefit of the buoyancy of the air in my lungs. From a motionless vertical position I exhaled completely and, as one would expect, I sank to the bottom. I came back to the surface and attempted to stay there with lungs mostly empty by managing my breathing the OPPOSITE as when I was floating motionless - inhaling/exhaling quickly and holding my breath OUT. As I was negatively buoyant at this point, it was going to be necessary to move my arms and/or legs to stay at the surface. However, I didn't need to do very much. I was able to keep my entire head above the surface with VERY little effort. I kept my ankles crossed and merely sculled my hands/arms slowly, every few seconds. I did this for 10min with no problem at all... could have done it for an hour or more.
So I found that a person with little body fat with full lungs needed ZERO effort to remain at the surface, and with empty lungs needed very little effort to do so. However, this next exercise was the interesting part...
For my final try, I attempted to keep my head above the surface by kicking my feet and sculling with my hands and arms. I didn't utilize my breathing to control my buoyancy, but simply breathed as needed to support the level of physical activity in which I was engaged. I didn't do this in "frantic mode" but did try to move with the same level of vigor with which we see the typical OW student conduct their tread. I was completly surprised at how very strenuous - and largely innefective - this approach was in keeping my head above water. And, it got worse as time went on. As I started to get fatigued my breathing became labored, my kicking and sculling became less effective, and I had to work harder at keeping my head above water and/or hold my breath briefly as my mouth/nose ocassionaly dipped under the surface. It was a vicious cycle. Completing the task was not impossible, but I was genuinely glad when the 10min was up. This approach was not only much harder than either of the other two, and not only far less effective at keeping my head abover water... it actually seemed to pull me UNDER the water as much as it kept me above the water.
So, it occurs to me that it's unfortunate that we ask students to do their tread at the BEGINNING of the course... long before we ever give them any information about how to control their buoyancy with their lungs or convey the importance/efficiency of economy of movement.
Does anyone actually demonstrate this "skill" prior to asking students to do it? I know I'm going to start doing so!
Ray
- It's nearly impossible for a human with air in their lungs to be negatively bouyant, certainly not SIGNIFICANTLY so
- Ultimately, anyone can float/tread for 10min with no problem at all
After my morning swim of 3,000m (so I was good and tired) I swam out to the deep end and tried to float. Laying on my back with a normal, full breath my feet sank under me. As I settled in to a vertical position I was able to float with my head tilted back so that my chin, mouth, nose, and ears were out of the water. By controlling my breathing I was able to float this way for 10min without any sculling/kicking at all - arms crossed at my chest, legs crossed at my ankles. This was at 6am this morning. I could easily still be there floating motionless now if I wanted to be.
Next I tried to manage keeping my head above water in this same position with my lungs empty. I wanted to see how much effort was required to make up for not having the benefit of the buoyancy of the air in my lungs. From a motionless vertical position I exhaled completely and, as one would expect, I sank to the bottom. I came back to the surface and attempted to stay there with lungs mostly empty by managing my breathing the OPPOSITE as when I was floating motionless - inhaling/exhaling quickly and holding my breath OUT. As I was negatively buoyant at this point, it was going to be necessary to move my arms and/or legs to stay at the surface. However, I didn't need to do very much. I was able to keep my entire head above the surface with VERY little effort. I kept my ankles crossed and merely sculled my hands/arms slowly, every few seconds. I did this for 10min with no problem at all... could have done it for an hour or more.
So I found that a person with little body fat with full lungs needed ZERO effort to remain at the surface, and with empty lungs needed very little effort to do so. However, this next exercise was the interesting part...
For my final try, I attempted to keep my head above the surface by kicking my feet and sculling with my hands and arms. I didn't utilize my breathing to control my buoyancy, but simply breathed as needed to support the level of physical activity in which I was engaged. I didn't do this in "frantic mode" but did try to move with the same level of vigor with which we see the typical OW student conduct their tread. I was completly surprised at how very strenuous - and largely innefective - this approach was in keeping my head above water. And, it got worse as time went on. As I started to get fatigued my breathing became labored, my kicking and sculling became less effective, and I had to work harder at keeping my head above water and/or hold my breath briefly as my mouth/nose ocassionaly dipped under the surface. It was a vicious cycle. Completing the task was not impossible, but I was genuinely glad when the 10min was up. This approach was not only much harder than either of the other two, and not only far less effective at keeping my head abover water... it actually seemed to pull me UNDER the water as much as it kept me above the water.
So, it occurs to me that it's unfortunate that we ask students to do their tread at the BEGINNING of the course... long before we ever give them any information about how to control their buoyancy with their lungs or convey the importance/efficiency of economy of movement.
Does anyone actually demonstrate this "skill" prior to asking students to do it? I know I'm going to start doing so!
Ray