So ironic, the people who need vibrational G forces the most are buying machine that start out at such high levels that they don't get the G forces they want because they have to bend their knees which reduces the ballistic impact of the plate hitting your feet. Locking the knees brings the linear vibration up to the spine. Many people have bad backs and don't get the beneficial G force they need because of this.
Most people are acidic that have bad backs and if using a vibration machine that gave enough G force at 5 to 6 hertz or below, they wouldn't need to lock their knees and would get the flushing G forces that open up the "one way valves" in their lymphatic vessels that people ask about that is probably the root of the problem that is causing the bad knees. Most people that have bad knees from and injury is another thing but having a body that leaches minerals from the bone, even the best machines may not help if the problem causing the bone density problems are first addressed. Again, most people who have knee pain are so ignorant and are buying the wrong machine. Like I said earlier, I have never talked to a salesperson selling a vibration machine who ever said, "buy someone elses machine, mine is not right for you".
Some machines vibrate at low speeds and others at high speeds over 20 hertz (not 20 speed settings) that helps build bone density. If someone needs to flush the toxins out and also wants to build bone density, the range should be from 5 hertz to 6 hertz on the lymphatic range to flush and over 20 hertz for enough G force to help for bone density issues.
It is a very easy to get the machine that can give you benefits if someone already has knee problems or a knee replacement, even.
If buying a machine that starts out over 5 to 6 hertz, bending the knees makes the vibration go to the muscles instead of the bones.
Knee Pain & Vibration Machines in a NutShell
The people who need vibrational G forces the most may end up with a machine that is too fast to realize the main benefit: lymphatic drainage. To allow the lymph to travel through the one-way locks and channels, you need to go slow enough for them to open and close. When you buffer the ballistic impact of the plate pushing your feet by bending your knees, you are losing the benefit of lymphatic circulation. Locking the knees brings the linear vibration up to the spine. If you get back pain, the solution is to slow the vibration down, way down, to 5 cycles per second. Most people with knee and back pain are not going to hear the salesperson say "buy a different brand, mine is not right for you" - they will likely end up not receiving the main benefit - lymphatic circulation.