To Erg or Not to Erg Landis Walsh

To Erg or Not to Erg Landis Walsh Biology 438 3. 31. 16

What is Erging • Cross-Fit tool • Training tool for rowers • Terminology • Drive vs. Recovery • Catch vs. Finish

Amateur Example

Why Should You Care? From a training perspective Reduced force generation limits power output Reduces training benefit One trains the wrong muscles From a safety perspective Improper form can put unwanted stress on other muscles For Example: eccentric force/load

Questions How does proper form affect force output on the erg? Will force output change? Do the biomechanics change?

How does the erg calculate watts? Watts=2. 8/pace 3 Pace determined from physics principles Machine measures rate of acceleration of flywheel during stroke and its deceleration Using this and known Moment of Inertia, can calculate speed, power, distance, energy usage Pace is time is takes to move 500 meters Physics: I=mr 2 T= (radius)(F)=(mαx radius)(radius)=Iα

Methods Filmed at 240 frames/second Frequency of stroke and recovery approximately set to 30 strokes/minute Analysis of Drive only Logger Pro- one out of every 10 frames were analyzed Adjusted Origin- Plane was uneven on both Assumptions: Point at which drive began and ended, participants were approximately same height and weight, same total frequency, generalizations about average power produced Calculations through Excel

Data: Videos

Analysis: Logger Pro

Analysis: The Handle Why the handle? Where generation of force is measured by the erg: Novice: • Total Horizontal Distance=2. 23 m • Total Time/Stroke =0. 917 seconds • Average power produced during stroke =250 watts • Average Force generation= 105 Newtons Experienced: • Total Horizontal Distance=2. 24 m • Total Time/Stroke =0. 792 seconds • Average power produced during stroke = 435 watts • Average Force generation= 156 Newtons

Data: The Handle Experienced: Handle Velocity vs. Time 3. 5 Velocity (m/s) 3 2. 5 2 1. 5 1 0. 5 0 0 0. 1 0. 2 0. 3 0. 4 0. 5 Time (seconds) 0. 6 0. 7 0. 8 0. 9 1 Velocity (m/s) Novice: Horizontal Handle Velocity vs. Time 4 3. 5 3 2. 5 2 1. 5 1 0. 5 0 0 0. 1 0. 2 0. 3 0. 4 0. 5 0. 6 Time (Seconds) 0. 7 0. 8

Conclusions: The Handle Experienced generates more force: 156 N vs. 105 N Experienced rower reaches max velocity earlier Max Velocity only slightly greater for novice (3. 37 vs. 3. 33 m/s) Smaller decrease in velocity towards end of drive 2. 20 vs. 2. 64 m/s Holding speed for longer period of time Note less time spent on drive for experienced (0. 792 vs. 0. 917 s) Almost 15% less time spent on drive While total frequency remains approximately the same (3031 spm) More time spent relaxing for experienced

What is Happening? Clearly, novice rower cannot match all of the physical parameters of experienced rower But why? Two biomechanical parameters that were measured: Hips Shoulders

Analysis: Hips Novice: • Total Horizontal Motion= 0. 827 m Experienced: • Total Horizontal Motion= 0. 560 m • Vertical Motion • Up- 0. 010 m • Down- 0. 042 m • Vertical Motion • Down- 0. 082 m • Max velocity= 1. 88 m/s • Max velocity= 1. 33 m/s • Max decelerating velocity= 0. 066 m/s • Max decelerating velocity= -0. 002 m/s

Velocity (m/s) Data: Hips 2 1. 8 1. 6 1. 4 1. 2 1 0. 8 0. 6 0. 4 0. 2 0 -0. 2 0 Experienced: Horizontal Hip Velocity vs. Time 0. 1 0. 2 0. 3 0. 4 0. 5 Time (Seconds) 0. 6 0. 7 0. 8 0. 9 1 Novice: Horizontal Hip Velocity vs. Time 2 Velocity (m/s) 1. 5 1 0. 5 0 0 -0. 5 0. 1 0. 2 0. 3 0. 4 0. 5 Time (Seconds) 0. 6 0. 7 0. 8 0. 9 1

Conclusions: Hips Experienced rower reaches maximum velocity faster 0. 209 seconds vs. 0. 375 seconds Novice Rower decelerates towards end of stroke more than experienced rower -0. 066 vs. -0. 002 m/s Novice rower wastes more energy on vertical displacement Up and down motion More horizontal motion (0. 827 vs. 0. 563 m) Due to more upright position at catch

Analysis: Shoulders Novice: • Horizontal Distance traveled=1. 59 m Experienced: • Horizontal Distance traveled=1. 60 m • Vertical Motion • Up- 0. 013 m • Down- 0. 296 m • Vertical Motion • Up- 0. 063 m • Down- 0. 314 m • Max Velocity=2. 75 m/s • Max Velocity=2. 76 m/s • Lull in velocity from 0. 333 -0. 417 seconds • No observed lull in velocity

Data: Shoulders Experienced: Horizontal Shoulder Velocity vs. Time 3 Velocity (m/s) 2. 5 2 1. 5 1 0. 5 0 0 0. 1 0. 2 0. 3 0. 4 0. 5 Time (Seconds) 0. 6 0. 7 0. 8 0. 9 1 Novice: Horizontal Shoulder Velocity vs. Time 3 Velocity (m/s) 2. 5 2 1. 5 1 0. 5 0 0 0. 1 0. 2 0. 3 0. 4 0. 5 Time (Seconds) 0. 6 0. 7 0. 8

Conclusion: Shoulders Novice “throws” the shoulders Suggested by decrease and then increase in velocity Both rowers have similar shoulder ”stroke” length 1. 60 vs. 1. 59 m Both exhibit pendulum motion Max Velocity very similar 2. 75 vs. 2. 76 m/s

Quick Recap Experienced Rower generated about 1. 5 x as much average force/stroke But why? Handle: Experienced rower spends 15% less time on drive Holds max velocity for a greater period of time Shoulders: Novice rower generates force by throwing shoulders Hips: Novice rower wastes more energy in vertical displacement Decelerates more at finish and more upright at catch

Future Directions Add force plates to the Erg Analyzing generation of force over time more accurately Instantaneous watts Analyzing force generation with respect to position in drive Analyze Angular Back displacement Does setting your back position at different angles help?

Acknowledgements Dr. Berner, Dr. Rome, and Dr. Nelson Penn Multimedia Department

Data: Videos

Data: Videos

Analysis: Logger Pro