Wednesday, December 27, 2006

Fixed vs. Dynamic Ergs

As I mentioned in my last post, Ivan Hooper, Sports Medicine/Sports Science coordinator for Rowing

Australia and Sports Physiotherapist at the Australian Institute of Sport, wrote a review of some studies in June of this year that looked at erg use. This review prompted several emails to Hooper on the merits of static vs. dynamic ergs. Hooper then wrote a follow-on piece in response.

In his response, Hooper states that:

- If you sit at front-stops on an erg and then push your legs down you move backwards relative to room by an amount equal to your leg length

- If you sit at front-stops in a single and then push your legs down (oars out of the water) you only move backwards relative to the bank by an amount ~20% of your leg length - the rest of the motion is taken by the boat moving away from you.

He goes on to note that:

The weight of the Rowperfect mobile power head is approximately 19kg, which is not that dissimilar to the weight of a single scull. This is the weight that an athlete’s leg drive is moving every stroke. Hence the manufacturer’s claims that the mechanics of the Rowperfect and on water rowing are similar.

Hooper says that the weight of a Concept II erg with sliders is about 35kg, heavier than a single and heavier than a Rowperfect. This leads him to believe that "sliders probably go a long way to replicating the mechanics of on water rowing, but still involve forces nearly double that of the Rowperfect." He makes several other points when discussing a static erg:

This kinetic energy, and / or inertia, has to decrease to zero for a change in direction to occur, thus something has to exert or absorb forces. Coming forward this force is absorbed by passive tissue structures of the knees resulting in an 8-10% increased leg compression (Kleshnev, 2005). It is reasonable to assume that the lumbar spine also absorbs some of this kinetic energy, creating an increase in lumbar flexion. Holt et al (2003) supported this when studying the effects of prolonged ergometer rowing. Over a 60 minute piece there were significant increases in the lumbar spine range of motion at the catch and total lumbar spine range of motion.

At the finish it is the large hip flexors that act to decrease and reverse the kinetic energy of the trunk (Rekers, 2006). This places very high loads on the lumbar spine, equivalent to doing prolonged sit ups. This places large sheer forces across the structures of the lumbar spine, potentially contributing to injury (Stallard, 1994).

When he discusses Kleshnev's findings that the legs work in a slower, static motion on a stationary erg, he says that

This may be an aspect that coaches wish to utilise if they are looking to enhance leg training, but I question the value of this when the load and contraction speeds are significantly different to on water rowing. The other issue is that once the legs fatigue, the trunk then becomes a greater contributor to total work performed. As mentioned above, this leads to a fatigue of the trunk muscles, placing lumbar spine structures at higher risk of injury.

In conclusion, the information that is currently available supports the idea that ergometer use is a risk factor for lumbar spine injury. It also suggests that the Rowperfect places much lower detrimental forces on the rower than the Concept II. It seems that placing the Concept II on sliders is also a way of reducing these detrimental forces, but this is probably not as effective as the Rowperfect.

Hooper concludes by making several interesting recommendations, beginning with a reduction in volume of work done on stationary Concept IIs. I'm surprised that research findings like these aren't more widely discussed. There is a huge amount of inertia in the rowing community working against any sort of wholesale change to a new type of ergometer starting with USRowing's testing procedure that makes exclusive use of the Concept II. It would seem, however, that when an alternative training machine exists, that better simulates on-water rowing while easing the stress on rowers' bodies, it would be given some serious consideration.

I'd immediately switch some of my training over to a Rowperfect if only I could find one of the darn things!

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1 comment:

Anonymous said...

There is a delicate balance between power and technique in rowing, and this needs to take place even on ergs. Some coaches may not stress the technique on ergs as much because they want their rowers to have fast times. These fast times can be achieved quicker if technique is thrown out the window, but this also leads to more injuries. This is only shown more when the practices are longer pieces because it aggitates the injuries more. So it may not be so much from the actual machine that a person is using as it is the technique and coaching that they are recieiving. The erg time is not the end goal in rowing, it should merely be used as a training device to produce fast boats.