In our announcement of PULSE, we famous that we made updates to a number of the metrics which might be calculated by the sensor. These modifications had been:
- Extra correct weighted ball elbow torque
- Eradicating shoulder rotation from the app
On this submit, we’ll go into how we made the modifications and what it means for you as a consumer.
Elbow Torque and Weighted Balls
In ASMI’s published paper evaluating the biomechanics of throwing with totally different weighted balls, they discovered that as ball weight elevated, elbow varus torque decreased.
We had related findings in our own pre-print on the identical topic. However after we appeared on the impact of various ball weights on elbow torque in Motus, we discovered the alternative — that as ball weight elevated, so did elbow torque.
To substantiate the findings, we collected paired movement seize and Motus information throughout all totally different ball weights, from 3 oz. as much as 2.2 lbs., to see what the precise distinction was. Our lab confirmed the findings above — as ball weight elevated, torque decreased.
In Motus, nevertheless, the torques elevated.
To appropriate for this, we modified the physics engine in PULSE to calculate elbow torque extra precisely when throwing weighted balls. Now if you throw with a non-competition ball weight tagged in dwell mode, elbow torque is appropriately measured.
How does this have an effect on you?
Extra correct elbow torque information means extra correct workload information.
Workload estimates are based mostly on the torque measurement of every throw. If the torque measurement is overestimated, then the workload estimate is over-exaggerated. If workload is over-exaggerated for heavy balls, we’d counsel an improper quantity of workload within the following days.
For instance, if a 6-foot, 200-pound pitcher threw 20 blue plyo balls (450g) and chosen the ball weight, his at some point workload can be one full unit greater than it ought to have been.
It’s necessary to notice that the modifications we made solely matter if ball weights are chosen for each throw you make.
This begs the query: what for those who don’t ever modify the ball weight? Will your workloads and A:C Ratios be affected?
The reply is sure, however not meaningfully so.
By not tagging the ball weight, you’ll get an underestimated workload for throws with heavy balls, and an overestimated workload for throws with mild balls.
In a throwing program that comes with each heavy and light-weight balls, nevertheless, the errors usually cancel one another out.
Once we ran our personal inside checks on numerous throwing exercises, we discovered a ~6 % error in workload of untagged vs. tagged classes.
For any individual with who’s on-ramped, a 6 % improve or lower would have lower than a 0.01 improve or lower in A:C Ratio.That’s nothing.
So is tagging ball weight going to lead to extra correct workloads? Technically, sure. However the distinction in doing so simply isn’t price it — particularly for those who’re a coach making an attempt to implement PULSE with a staff.
The juice isn’t definitely worth the squeeze.
In case you’re doing analysis with PULSE nevertheless, you possibly can relaxation assured that the elbow torque metrics are lab correct for weighted balls.
Shoulder rotation in Motus was a measure of most exterior rotation — or the quantity of layback — that an athlete skilled throughout the throw.
When validating this metric in opposition to our movement seize lab, nevertheless, it simply wasn’t legitimate or dependable. Throughout athletes (inter-subject), it was a dependable metric; we noticed a correlation coefficient of 0.34.
Inside athletes although (intra-subject), the correlation coefficient dropped to 0.03, indicating little to no reliability. Be aware the inter-subject black trendline in Determine 2 under.
We’re not going to deceive you. This metric isn’t correct. It isn’t dependable. And we’re not going to feed you one thing through which we aren’t assured. Due to this fact, we’ve eliminated shoulder rotation from the app.
At Driveline, we at all times purpose to provide the most correct and highest-leverage info. We’re not afraid to confess that one thing was improper, and, by golly, we’re going to repair it. With these modifications, we’re taking a step in that path.
Whereas these updates had been geared toward bettering the worldwide accuracy of the sensor and its workload measures, we’ve our sights set on the subsequent enchancment: evaluating your mechanics with PULSE.
Written by Joe Marsh