Choosing the right frequency type
If trying to build bone then anything over 20 hertz speeds up the process although machines under 14 hertz can still help but just takes longer. The amplitude is the 2nd most important thing to look at after deciding if you need a machine that goes over 14 hertz. For high acceleration strength training it is very hard to get the 10 minute workout if the machine stays under 14 hertz.
Repetition is more important than amplitude when it comes to bone density but amplitude is more important when trying to drain lymph. If the amplitude is too high it can be hard to stand with your legs less bent so the body can absorb the G forces up the legs and into the spine. Most people don't stand on the tippy edge anyway
Note: Two machines can have the same G force and the same size plate but the "sine wave" motion, or the milking motion can be different between machines. Some machines have the G force spread out through the entire range of upward displacement and others give most of the G force at the first 10% of the upward movement of the plate.
When the speed of the plate is higher, a higher amplitude takes more metal to stabilize the plate. I look for vibration plate that run smooth at high amplitudes and high speeds. The Hypervibe Performance and Vivovibe 460 are examples of machines that can handle top speeds.
Choosing the right displacement with frequency
When a lower displacement (peak to peak measurement of plate movement) machine is needed and when it is not
If leaning on heels for a great lymphatic and bone density effect, most people on most machines naturally gravitate to positioning their feet a few inches in from the edges of the plate. By bringing the foot position inward this reduces the magnitude of the acceleration because of the reduced displacement the person experiences. In fact I tracked a couple classes of people who were using 20 vibration machines and I noticed that very few people stand on the edges. The ones who were generally I could tell were better trained and were in a deeper performance squat in order to handle the Gforce and challenge to core stability.
The issue those with using most brands of machines is that their Gforce is pretty low to begin with somewhere in the range of .5 - 5.4Gs on 95% of machine re-brands. So moving the feet position inwards cuts that magnitude quite substantially so most people are not getting very significant acceleration on the body. I have interviewed customers and individuals who frequent vibration studios and the consensus is that they don’t like big displacement during really high frequency and GForce sessions. It’s challenging! So while it would be good to challenge the body most people let comfort ultimately guide their workout routine and thus affect the potential health goals they can reach.
I think the new design of the Hypervibe G17 was smart in reducing the displacement to 7mm. Granted at such high Gforce and Speeds up to 35hZ (validated and proven spec) trying to stand on a plate at 11-12mm at that intensity would be something very few people could do. By reducing the amplitude and displacement it allows a person to more feasibly work their way up to more intense usage in terms of the Gforce they expose their bodies to. Standing on the G17 at 20hZ for example was a lot easier then the Hypervibe performance at the same speed. Now granted easier does not always mean better but if I wanted to push myself to go beyond that speed and to higher Gforce the G17 could make that more achievable.
So there are some real technical advantages to having less displacement but only if the machine can really supply mega acceleration power behind it. For most machines they need larger displacement to make up for weaker motors and turntable mechanisms and slower frequency ranges.
The G10 and Hypervibe Performance (original model) are exceptions to that however as those machines have standard displacement and also can pull the higher speeds and high Gforce combinations.
With those models, which are most popular for home users, a person can still find that super comfortable stance a few inches inside of the edges of the plate and get that 7mm but still get plenty of Gforce effect. The G17 is really designed for overweight individuals, serious athletes or commercial settings with a big volume of users. The way I look at it as a home user seeking to get specific health benefits one either has the choice between low Gforce machines where most people feel comfortable around the 7-8mm foot position, or use a higher Gforce machine where one can get more health benefit potency and still be comfortable in the same foot position.