[Matt Jordan]

Hi Ryan

Sorry for the delay on my response. PASCO plates have been shown to be both reliable and valid. The one issue is that they aren’t overly durable and they can start to drift if someone makes a hard landing on one of the corners that houses the load cell. The load cells can be swapped out (apparently) or you can purchase another plate for cheap ($500).

The one issue with PASCO is that they don’t come with any software to analyze the jumps. This means that you have to either: (a) figure out how to do that yourself; (b) buy software like Force Decks that can acquire PASCO data and run the numbers for you. By the time you buy the software, you are probably getting close to the price of the Hawkins plates.

I have never worked with Hawkins myself but lots of my friends use their hardware and software, and they speak very highly of it. I have worked a bit with Force Decks and have even compared our analyses. They are (and should be) quite similar.

The whole thing with the analysis is that once you determine the start of the jump and the system force of the athlete (I say system because if you are doing a loaded jump, this would include the external load) the rest of the calculations are pretty straightforward (time integration and picking either phases of interest from the velocity of the body centre of mass or discrete time points of interest like the force at V0).

The things that really make the difference in my opinion are: (a) the accuracy, precision and range of the force plate – for example, suppose you have a force plate that can measure up to 20,000 N – the tradeoff here will be that the precision in lower force ranges like the ones we measure in jumping may not be sufficient; (b) durability – as described above, this is a big limitation with PASCO – in the Lesson on Integrating Force Plates into the Daily Training Environment I detail the issues of not detecting a malfunctioning force plate; (c) any sort of signal filtering that may occur.

We will be organizing another online discussion forum in the next few weeks so we can talk more about this if you want.

[Matt Jordan]

Hi Kohei

Thanks for the question. At our institute, we managed to find an old Cybex dynamometer that a sports medicine clinic was getting rid of. We instrumented it with a commercial load cell so that we can do isometric strength testing (including rapid force production ability – RFD). This allows us to assess the knee flexor strength curve and the explosive strength curve (RFD-joint angle relationship). I understand that not all strength coaches will have access to this so good alternatives are: (1) as you described, use a Pasco force plate on a box with a bar over the hips, and have the athlete push down into the plate at different knee joint angles; (2) use a handheld dynamometer.

You may see this as not worth the time but lots of research suggests that our strength capacity at our joints shapes complex movement strategies. This is also evidenced by observations of differences in vertical jump force-time asymmetries between patients receiving a bone patellar tendon bone autograft and those receiving a hamstring tendon. The relative loss of either knee flexor or extensor strength results in different lower limb loading patterns.

Taken together, I think this is a key thing to pinpoint during rehab.

My go-to would be the Pasco force plate on a box if I didn’t have a dynamometer like a Cybex.

Matt

[Matt Jordan]

Hi Juan

I think you probably saw the email but the online discussion is now posted on our course along with all of the discussions and think tanks from previous courses.

[Matt Jordan]

Hi James

Thanks for the question! To the best of my knowledge, I am not aware of any studies that have looked at monitoring using a loaded jump protocol. But, speaking from experience, we have done this! The main findings from this project are: (a) there is a divergence between the effects of performance fatigability on load versus unloaded jumping – the unloaded conditions tend to decrease more with fatigue than the loaded conditions, especially when the loaded condition gets to within 100% of body mass; (b) the recovery of unloaded vertical jumps is slower after a training block.

If I had to guess, I would think that the underpinning mechanism would be prolonged low frequency force depression or low frequency fatigue (LFF). LFF tends to impair rapid force production (RFD) and maximal muscle power whereas maximal muscle strength is generally less impaired by LFF.

I do think this approach makes sense, especially with athletes who need to express force across a range of movement velocities (slow to fast). Because time is often of the essence though, unloaded jumping is probably the most efficient.

Surprisingly, there is next to no scientific studies linking performance fatigability to injury. The best we can do is observe that movement strategies, muscle activity (intermuscular coordination), and RFD tend to become impaired with fatigue. And, movement strategies and muscle activity patterns associated with potential injury mechanisms tend to arise in a fatigued state.

There is a recent systematic review on the topic:

Verschueren J, Tassignon B, De Pauw K, Proost M, Teugels A, Van Cutsem J, et al. Does Acute Fatigue Negatively Affect Intrinsic Risk Factors of the Lower Extremity Injury Risk Profile? A Systematic and Critical Review. Sport Med [Internet]. 2020;50(4):767–84. Available from: https://doi.org/10.1007/s40279-019-01235-1

Thanks for posting the question. Interested to hear what others have to say.

mjj

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