Interesting research paper and discussion on indoor rowing

[xeno]

using static rowing and dynamic rowing, slides versus no slides etc



Friday, September 15, 2006
Training on Static Rowing Machine Discussion, from Ivan Hooper 14/06/2006

A Discussion of Rowing Ergometer Use

Following on from my recent email regarding injury and illness statistics, I would like to raise some comments and considerations regarding the use of ergometers for training. I have noticed that there seems to be a trend towards increasing use of the ergometer in training, particularly doing low rate work down to ratings as low as 12. I understand the benefits that this type of work can produce, but I would like to make you aware that this form of training is not without risk of injury.

In some of his regular newsletters, Valery Kleshnev highlighted the fact that the kinetics and kinematics of ergometer rowing are different from that of on water rowing. On an ergometer, the handle force has a higher peak and develops later, the stroke length tends to be 3-5% longer and the curve of foot stretcher force is considerably moved towards the beginning of the stroke. An important point is that the legs:trunk:arms proportions of power development on an ergometer are 37%:41%:22% compared to 45%:37%:18% for on water rowing. This means that the trunk is doing a larger proportion of the work on an ergometer. I believe all of these factors lead to an increased load applied to the structures of the trunk, and particularly the spine. Greater work done by the trunk could produce earlier fatigue of the trunk muscles, placing the spine at risk.

Holt et al (2003) studied the effects of prolonged ergometer rowing. Over a 60 minute piece there were significant changes in the way the athletes moved. Lumbar spine range of motion at the catch and total lumbar spine range of motion increased during the piece. The gradient of force production decreased, and the ratio of drive to recovery time increased, over the piece. The authors attributed these changes to fatigue of the trunk muscles during the piece, reinforcing that fatigued trunk muscles may lead to low back injury.

Teitz et al (2002) conducted a retrospective study of 1632 US intercollegiate rowers. By the use of detailed questionnaires they established that 32% of these athletes had experienced back pain of at least one week's duration during their rowing careers. The use of rowing ergometers for greater than 30 minutes per session and free weights were the variables most consistently associated with back pain.

In my experience, I feel that athletes often pay little attention to their rowing technique when on an ergometer. The level of coaching supervision is often limited as well. The result is that athletes spend time on the ergometer under greater trunk load than when on the water, with poor technique and poor postural positions. The end result is an increased load on the spine which can increase the risk of injury.

It is very common for athletes to report that they feel that the ergometer was highly related to their back pain. And those athletes with current back pain regularly report that ergometer rowing aggravates their pain more than on water rowing. When this feedback occurs over a significant number of athletes over a number of years it is difficult to dismiss.

Unfortunately I believe that we are seeing an increase in the number of low back injuries amongst rowers. The three month injury and illness statistics that I recently sent to you highlighted the fact that back injuries are having a significant effect on team preparation, both at an individual and crew level. Even though I am sure that there are many causes of this increase in back pain, evidence and experience suggests that ergometer use is a significant one.

While I am the first to acknowledge that the ergometer is a powerful training tool, I ask coaches and athletes to give due consideration to the risks involved. Please consider the time spent on the ergometer, the rates that training is done at, the supervision provided and how diligently athletes concentrate on their technique.

I hope that we can all work towards a reduction in low back injury rates. For every back injury that we avoid, that is an extra 30 days (on average) that the athlete can spend training properly! Any feedback regarding this subject would be most welcome.

References:

Holt P J E et al. Kinematics of spinal motion during prolonged rowing. International Journal of Sports Medicine 2003; 24: 597-602.

Kleshnev V. Rowing Biomechanics Newsletter; www.biorow.com :April 2001.

Kleshnev V. Rowing Biomechanics Newsletter; www.biorow.com :October 2003.

Kleshnev V. Rowing Biomechanics Newsletter; www.biorow.com :January 2005.

Teitz C C et al. Back pain in intercollegiate rowers. The American Journal of Sports Medicine 2002; 30 (5): 674-679.

posted by XENO @ 7:46 PM 0 comments

Dynamic rowing machines versus static rowing machines from Ivan Hooper 15/09/2006

A Discussion of Fixed vs Dynamic Ergometers
Since I sent out some comments regarding ergometer use, I have had quite a few emails back regarding the use of the Row Perfect ergometer, or putting the Concept II ergometer on sliders. I am aware that there is some work underway investigating this issue, but currently there are not a lot of papers that have been published.
In working through some of the literature I came across a website that goes some way towards explaining the physics of ergometer rowing (Dudhia, 1999). It discusses that a fundamental difference between the linear mechanics of a ‘static’ ergometer (such as a Concept II) and a boat can be illustrated by the following test:
• 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.
This is a result of the action-reaction principle (Newton's 3rd Law). The force applied by your legs to the stretcher acts equally on you and the stretcher. In the static case (ergometer), the stretcher is effectively attached to the whole planet so doesn't move - you do all the moving. In the dynamic case (boat), the mass of the single scull is much lighter (typically 10-20%) than you, so it moves further than you do.
This is not just a matter of the frame of reference: in the static case (ergometer) you are actually performing more work accelerating your whole body weight up and down the slides, thereby creating high levels of kinetic energy. In the dynamic case (boat) your body weight is relatively stationary, creating much lower levels of kinetic energy and thus requiring less work to be done to reverse this kinetic energy. It results in an athlete needing to put in six times more energy just accelerating and decelerating their own body weight, compared to on water rowing.
A ‘dynamic’ ergometer, such as the Row Perfect, attempts to simulate the mechanics of on water rowing by having the stretcher/flywheel also mounted on a rail. Attempts have been made to simulate the same effect by mounting the Concept II on sliders.
Most of the literature that I have read was performed examining the Row Perfect ergometer in a mobile and fixed state. The weight of the Row Perfect 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 Row Perfect and on water rowing are similar.
The weight of a Concept II is nearly 28kg. When you include the mobile component of the sliders, the weight is around 35kg. If you consider the mechanics discussed earlier, when a Concept II is mounted on sliders there would be more motion of the rower and less motion of the ergometer when compared to the Row Perfect. Hence, my thinking is that sliders probably go a long way to replicating the mechanics of on water rowing, but still involve forces nearly double that of the Row Perfect.
There are two recent papers that have both described the mechanics of static versus dynamic ergometers, using the Row Perfect in both a dynamic and fixed state. Bernstein et al (2002) found that average stroke length on the static ergometer was 53mm longer. They discussed that this is due to the higher kinetic energy associated with moving the whole body mass, as was discussed earlier. Colloud et al (2006) also discussed the higher inertial forces generated during the transition between the recovery and propulsive phases, especially at the catch.

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).

Both Bernstein et al (2002) and Colloud et al (2006) found higher maximum stroke forces and power when using the static compared to the dynamic ergometer. They suggest that the passive structures of the rower’s joints could be loaded more at the catch on the static ergometer when the lower limb joints and trunk are fully flexed. They both propose that these higher forces, imposed over a longer stroke, may be associated with injury.

Undoubtedly, higher forces applied over a longer distance means more work done by the body’s muscles. More work done means earlier fatigue. Fatigued lumbar spine muscles may allow even more lumbar flexion, transferring higher forces to the passive tissues of the spine. The combination of lumbar flexion and muscular fatigue has long been identified as a cause of lumbar spine injury amongst rowers (Reid & McNair, 2000).

After repetitive motion, protective muscle activity has been shown to be reduced, often for a number of hours after the exercise is completed (Gedalia et al, 1999) The ramification for rowers is that, during this period, the athlete may be more vulnerable to injury, even when they may not be experiencing high loading on the spine (Reid & McNair, 2000). Ergometer use and weight training are two modalities that are likely to load the trunk muscles more than on water rowing. Based on the findings mentioned above, placing these two training modalities in close proximity is likely to increase injury risk.

In discussing ergometer versus on water rowing, Kleshnev (2005) noted several differences. He stated that the legs execute more work on a stationary ergo, but in a slower static motion. On the water the legs work much faster at the catch, when the force is not very high and therefore execute less power. In this aspect a dynamic ergometer stands somewhere between a stationary ergometer and on water rowing.

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 Row Perfect 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 Row Perfect.

At this point in time, the Concept II is the standard for conducting physiological testing of the elite rower. I do not propose that this change immediately, but I do think that what machine we test on in the future needs further examination and evaluation. Issues such as injury risk and physiological specificity need to be considered when selecting the most appropriate way to test our athletes.

In summarising the information that is currently available regarding ergometer use and its effects on injury, I would like to make the following recommendations:

• Reduce the volume of work done on Concept II ergometers in the stationary setting.

• Keep the maximum length of a piece on an ergometer less than 30 minutes. If more than 30 minutes is to be done in a session, make sure that the session is broken up into shorter pieces with appropriate rest and stretching in between the pieces.

• Where appropriate, use either the Row Perfect or Concept II ergometer on sliders.

• Where appropriate, use other forms of cross training. Consider using cross training in conjunction with ergometer training in order to achieve the necessary training volume.

• Endeavour to place ergometer sessions and weights sessions on separate training days, or at least several hours apart.

• Provide good supervision of technique while athletes train on an ergometer. The level of attention to technical detail on an ergometer should be no different to when training on water.

• Ensure that athletes understand that the need for good technique while training on an ergometer is as important as when on water.

• Be aware that some people will never have problems on an ergometer, while others may have significant problems. Coaches should be prepared to individualise training programs to suit each athlete.

The recommendations made in this article are based on a balance between possible injury risks, and the acknowledged benefits of ergometer training. Ideally these recommendations are designed to stimulate thought when devising training programs. I would encourage coaches to consider both the potential benefits and the potential risks of all forms of training.

Finally I would like to remind everyone that coaches have a duty to make their crews as fast as possible, without causing damage to the people for whom they are responsible (Stallard, 1994). An ongoing challenge for all coaches is to minimise the potentially detrimental aspects of their training programs.



References

Bernstein I A et al (2002) An ergonomic comparison of rowing machine designs: possible implications for safety. British Journal of Sports Med; 36:108-112

Colloud F et al (2006) Fixed versus free floating stretcher mechanism in rowing ergometers: Mechanical aspects. Journal of Sports Sciences; 24: 1-15

Dudhia, A (1999) The physics of rowing: dynamic versus static ergometers. http://www.atm.ox.ac.uk/rowing/physics/index.html

Gedalia U et al (1999) Biomechanics of increased exposure to lumbar injury caused by cyclic loading. Part 2. Recovery of reflexive muscular stability with rest. Spine; 24: 2461-7

Holt P J E et al (2003) Kinematics of spinal motion during prolonged rowing. International Journal of Sports Medicine; 24: 597-602.

Kleshnev V (2005) Rowing Biomechanics Newsletter; Vol 5: No 1

Reid D A & McNair P J (2000) Factors contributing to low back pain in rowers. British Journal of Sports Med; 34:321-325

Rekers, C (2006) Personal Correspondence.

Stallard, M (1994) Regatta; 66, p22.

[Bob S.]

Thanks, Xeno. Excellent articles. It looks like I had better get my erg back on the slides and make a better effort to get used to using them.

Bob S.

[PaulS]

As indicated by the authors, this was a review of previous research. Though it was nice to go through it all (again) in an assembled fashion.

While the comparison between the weight of a Shell, RP flywheel assembly, C2 on Slides, and Grounded Erg (attached to the earth), always ends up with the authors declaration of the Shell and RP being "most similar", which IMO, is quite wrong, and here's why.

We don't row anywhere without first placing the blades in the water, i.e. connecting the shell to the Earth!, albeit perhaps not quite as firm a connection as the grounded C2 may have. The Mass of the Flywheel assembly is simply inconsequential, and an equilibrium state will be reached even if the mass of the RP flywheel assembly increased, say by adding weight plates to it, with no net effect on the pace displayed.

Conclusion:
If you are sitting on the Erg, not holding the handle and merely going through the motions of the stroke, indeed this is most like sitting in a shell with the blades flat on the water going thorugh simiar motions.

However, if we decide to square and bury those blades prior to executing a drive, we will no longer have that boat being moved in the direction of the stern, but advancing, and once a bit of speed has built up, the body is going to be displaced much further than merely the length of ones legs during the drive, a reasonable argument for a type of "super connection to the earth" (hydrodynamic lift) could quite easily be made. Now which situations are most similar?

The advantage to the "dynamic erg" in training people for better performance in boats is that it forces the athlete to use opposing muscle groups during the recovery to make it into the proper catch position, rather than letting momentum carry them there, exacly what needs to be done in a boat (the blades are out of the water and the hull is no longer connected very well to the earth during the recovery), since the hull is literally being dragged along under the rower by their feet attachment to the stretcher.

An excellent bit of feedback when on a "dynamic erg" is the amount of seat movement relative to the ground, and there are a couple of things to look for.
1) Minimal overall movement that would not exceed the ratio of Body Mass to Moveable Erg Mass.
2) Seat and foot stretchers should be moving away from each other, or toward each other during a stroke cycle. There may be a very brief moment they move in the same direction at the finish, but any movement in the same direction at the catch indicates a serious technical flaw that will kill boat speed.

As for the final recommendations, I see nothing unreasonable there other than the seemingly patronising tone, as if coaches haven't had exactly those thoughts and concerns in mind for many years. I've only been around Rowing for 24 years, but recall seeing my coaches taking the risks into concern even then, and while it might have been revolutionary, from reading the coaching notes of Steve Fairbairn it seems that the revolution happened well over a century ago.

[LJWagner]

Good articles, and follow up.

I will continue to spare my low back with my slight pivot prior to the catch, so I have a bit of lean to the bow on the drive, with good tall posture. Erging, and OTW should that ever happen again.

A slightly accelerated slide to the stern, if timed right, adds to boat speed up to the catch. Granted, execution is difficult to accomplish without stern check, but that is what practice is all about, isn't it ? Don't practice what is easy. Practice what can make you better.

Gus knows I love this topic.