Hello Coaches,
Rowing at lower stroke rates will require your athletes to generate a higher average force to achieve a target pace.
At training venues, boathouses and gyms all over the world right now, athletes are dutifully logging kilometers at low stroke ratings of 18-24 spm. While there are benefits to this practice, Concept2 has some concern over the impact of low stroke rate/high force work done during long training sessions. Coaches and athletes need to understand the effect of stroke rate on the average force required to achieve a desired power output or pace. At low stroke rate the average force will be significantly higher for a given pace. Account for this reality by targeting a slower pace during low stroke rate work. High volume, low stroke rate work at high power output has the potential for causing overuse injury.
Recently we rigged up a DYNO monitor in parallel with the normal Performance Monitor on an erg. This enabled us to get a reading on the average force generated during the drive portion of a stroke. We tested the effect of stroke rate on the force required to achieve various paces, and here is what we found:
| Drag | Pace | SPM | Average Force
in lbs. (kgs.)
during drive | Average Force
in lbs. (kgs.)
during drive
--erg on a slide |
|
120
|
2:00
|
18
|
127 (58)
|
127 (58)
|
|
120
|
2:00
|
24
|
105 (48)
|
97 (44)
|
|
120
|
2:00
|
30
|
84 (38)
|
83 (38)
|
|
120
|
2:00
|
34
|
83 (38)
|
78 (35)
|
|
120
|
1:45
|
18
|
174 (79)
|
177 (80)
|
|
120
|
1:45
|
24
|
143 (65)
|
142 (65)
|
|
120
|
1:45
|
30
|
115 (52)
|
111 (50)
|
|
120
|
1:45
|
34
|
110 (50)
|
108 (49)
|
What does this chart tell us?
- Rowing a 2:00 pace at 18 spm requires higher average force than rowing a 1:45 pace at either 30 or 34 spm.
- Rowing a 2:00 pace at 18 spm requires ~ 50% more force than rowing a 2:00 pace at 30 spm.
- Rowing a 1:45 pace at 18 spm requires 58% more force than rowing a 1:45 pace at 34 spm.
- Rowing with the Concept2 Slides had an insignificant effect on average force during the drive. It should be noted that rowing on the slide is usually done at higher spm, and as shown above, it is spm that has a large effect on force required to achieve a given pace.
During winter training, athletes are asked to row many more kilometers generating high average force at low stroke ratings, while the volume of work done at race intensities is low and intermittent. Consider this scenario as another way to look at the practice: if you squat 100lbs. (45 kgs.) @ a rate of 30 reps/minute for 7 minutes (7X30 = 210reps), you’ll move the weight every 2 seconds and your legs and back will be tired. If you squat 100lbs. (45 kgs.) @ a rate of 18 reps/minute for 40 minutes (40X18 = 720reps), you’ll move the weight every 3.3 seconds and your legs and back will be toast. Perhaps you want a training benefit from the 40 minutes of squats, but to effectively complete the training without damaging yourself, it makes sense to lower the weight being moved.
There are a few reasons why low stroke rate work might be an appealing option: a novice rower who is not able to coordinate the rowing motion comfortably; having more time to do so allows her to be effective; athletes who need to work on fundamental technique have an easier time doing so when the cadence is low; and, it is easier for less experienced athletes to maintain the ratio of low cadence rowing by feeling more resistance.
Basics:
Force applied over a distance = work. Work over time = power (which translates to pace on the erg). Often force is confused with power, and while related, they are very different. At 18 spm, stroke work is produced in 3.3 seconds. At 30 spm, stroke work is produced in 2 seconds. If we try for equal power, the equations look like this:
W is work at 18 spm.
w is work at 30 spm.
F is force at 18 spm.
f is force at 30 spm.
d is distance of the stroke and assumed equal at 18 or 30.
P is power and assumed equal at 18 or 30.
P = W/3.3 = w/2 W = F*d w=f*d
F*d/3.3 = f*d/2
F/3.3 = f/2
F = f*3.3/2 = f* 1.65
Force at 18 spm = force at 30 spm times 1.65 (the ratio of stroke duration time).
This relationship is in the ball park of our recent experimental findings!
Another factor:
This is what happens on the erg. As force is applied, the athlete is accelerating the mass of the flywheel and working against the resistance of the spinning fan. On the recovery, air resistance slows the flywheel down. The more time you devote to the recovery at low stroke ratings, the more the flywheel will slow down. At the slower flywheel speeds the athlete will be able to generate higher forces with slower body movements, in effect making it easier to generate a high force at low cadence. Note that this applies when rowing at low cadence on the water as well—a subject for another newsletter.
Sincerely,
Chris Wilson
chrisw@concept2.com
