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1

How to improve your technique

with biomechanics

Dr. Valery Kleshnev

Rowing Science Consultant

BioRow Ltd.

www.BioRow.com

kleval@btinternet.com

Joy of Sculling 21st Annual Conference

Saratoga, December 12-15th, 2013

www.thejoyofsculling.com

2

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Basic chart of Rowing Biomechanics

Medal

Work capacity

(Physiology)

Technique

(Biomechanics)

Motivation

(Psychology)

Life Style

(Management)

Efficiency = Pout / PinputEffectiveness = Pmax - Wmin

Rowing Style /

Rower’s Efficiency

Blade

Efficiency

Dynamics of

the system

Boat

EfficiencyRowing

Power

Segments’

Velocities RiggingForce

Curve

Boat Velocity

& Acceleration

Standards(Stroke Rate,

Length, Force)

Performance Level

Analysis Level

Measurement Level

Vertical Oar

Angle

From: Kleshnev V. Rowing Biomechanics Newsletter 2011/10 &

2011. Rowing Biomechanics. In: Rowing Faster, the 2nd ed., ed. Nolte V. Human

Kinetics

4

How we define rowing technique efficiency?

The three main parts of rowing as a process of

energy transformation

Propulsive PowerBlade

Propulsive

Efficiency

Minimal required Power

Boat Velocity

Efficiency

Mechanical Power

Internal

(muscle)

Efficiency

5

Efficiencies of the components of energy

transformation process during rowing

Internal Muscle

Efficiency 24±4%

O2

Handle power

Blade Propulsive

Efficiency 82±5%

Handle power

Propulsive power

Boat Velocity

Efficiency 94.5±1%

Boat Velocity

Drag Power

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Efficiency (%)

6

The highest amount of energy 93% is lost in the

rower’s body.

The Rower is the main area to improve rowing

efficiency.

1667

Total energy

consuming

400

Handle Power

328

Propulsive

Power

310

Minimal

Required Power

93.4%

5.3% 1.3%

Internal LossesBlade Shift Losses

Velocity Fluctuation Losses0

400

800

1200

1600

2000

Power (W)

Amounts and Losses of

energy in rowing

(example values)

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How can we increase the rower’s efficiency

and effectiveness?

Using of the most powerful muscle groups;

Optimisation muscles contraction velocities;

No energy absorption, single-motion movement;

Decreasing of muscles-antagonists activity;

Muscles relaxation during recovery phase.

8

What are Rowing Biomechanics “Gold Standards”?

Pprop = DF * V3

P = Pprop / Eblade

L = Inb. * A

WPS = P * (60 / Rate)

Fav = 0.83 * WPS / L

EventG.St.

TimeP (W) Inb. (m) Rate (1/min)

Angle

(deg)Fav (N) Fmax (N)

W1x 07:11.5 400 0.89 33.0 110 371 713

W2x 06:39.5 400 0.88 35.0 110 354 680

W4x 06:08.5 400 0.87 37.0 110 339 651

W2- 06:52.9 400 1.16 37.0 90 334 641

W8+ 05:53.1 400 1.15 39.0 92 313 601

M1x 06:32.5 550 0.89 35.0 114 464 892

M2x 06:02.1 550 0.88 37.0 114 444 854

M4x 05:33.2 550 0.87 39.0 114 426 820

M2- 06:08.5 550 1.16 38.0 90 447 859

M4- 05:41.0 550 1.15 40.0 92 419 806

M8+ 05:18.6 550 1.14 40.0 94 414 797

LW2x 06:47.0 330 0.88 35.0 106 303 583

LM2x 06:07.2 470 0.88 37.0 110 393 756

LM4- 05:46.2 470 1.15 40.0 90 366 704

Category W (kg) P (W) Erg Score (m:s)

Open Women 85 400 6:23

Open Men 95 550 5:44

LW Women 60 330 6:48

LW Men 70 470 6:03

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Input of body segments into rowing power

Legs produce nearly half of

rowing power;

Trunk produces nearly one

third of rowing power;

Arms produce about one

fifth of rowing power;

Arms, 22.70%

Trunk, 30.90%

Legs, 46.40%

15%

20%

25%

30%

35%

40%

45%

50%

20 25 30 35 40

Legs

Trunk

Arms

Power Shares (%)

Stroke Rate (str/min)

Legs increase their

percentage of power with

increasing stroke rate;

Arms’ power share

decreases, when the

stroke rate increases.

10

This tells us that the largest

capacity for increasing

rowing power can be found

from utilization of the trunk

work-capacity.

Utilisation of work-capacity of the body

segments Legs use up to 95% of their

power.

Trunk muscles utilize only

about 55%;

Arms’ utilization is about

75%;

(Kleshnev V. 1991)

Legs,

95%Trunk,

55%

Arms,

75%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Utilisation (%)

11

Velocity-Force dependence for isolated

muscle (Hill principle)

Hyperbolic relationship between velocity and force was discovered in the 1920s by Archibald Vivian Hill from a study of frog muscles.

A number of recent researches confirmed that it can be valid for complex multi-joint movements.

The highest power can be achieved at 1/3 of max. static force and 1/3 of max. voluntary velocity.

0%

50%

100%

150%

-40% -20% 0% 20% 40% 60% 80% 100%

0%

25%

50%

75%

100%

F

P

Force (%)

Velocity(%)

Power (%)

F = b1 / (b0 + V)

P = F VMax.

Power

Lengthening<->Shortening

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Utilisation of the Hill principle in rowing

Negative power is the most inefficient unless it happens during very short

time.

Too heavy or too light gearing can affect the force/velocity relationship and

thus efficiency.

An optimal body sequence, (i.e. rowing style) matched to the rower’s

characteristics and boat speed plays the most significant role in

rowing efficiency.

-2

-1

0

1

2

3

-60 -45 -30 -15 0 15 30 45

Total

Legs

Trunck

Arms

V (m/s)

-2

-1

0

1

2

3

-60 -45 -30 -15 0 15 30 45

Total

Legs

Trunck

Arms

V (m/s)

13

How we measure velocities of body segments?

Cable position transducers are attached to the seat and top of the trunk (at the level L7-Th1 vertebra or sternum-clavicle joints);

Arms velocity is calculated as a difference between handle velocity (derived from oar angle and inboard) and trunk velocity.

14

What effective dynamics means?

Front-loaded drive, trampoline effect;

Quick acceleration of the rower’s mass first, then

taking the load;

Emphasis on the stretcher push, “catch through

the stretcher”;

Smooth “fat” force curve, control through

suspension from the seat;

Using rower’s inertia for propulsion at finish, “finish

through the handle”.

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How the front-loaded drive looks like? It is important to

increase force

quickly up to 70% of

maximum;

“Trampolining”

effect?

1. Front-loaded 1. Middle-loaded

1

2

Drive

Force/Body mass (N/kg)

R3-D1 D2 D3 D41

2

Boat

Acceleration

1

2

Boat Velocity

16

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Why the front loaded-drive is more effective?

Front-loaded drive (F1):

Gives 47% higher average

velocity and distance

travelled during the drive;

Creates much more even

distribution of the power;

Provide better utilization of

the most powerful muscle

groups

Hydro-lift force on the blade

can be used better.

0

2

4

6 F1F2F3

Force (N)

0

5

10

15

V1

V2

V3

Velocity (m/s)

0

20

40

60

80P1P2P3

Power (W)

0

20

40

60 P1P2P3

Distance

travelled (m)

FA

17

How can we analyse the Force Curve?

Catch gradient defines how quickly the force increases;

Position of the Peak Force defines emphasis of force

application;

Finish gradient defines how long the force maintained.

0%

20%

40%

60%

80%

100%

0% 20% 40% 60% 80% 100%

Norm.Oar Angle (% to total)

Normalized Force (% of Max.)

70% of Max.

Catch

Gradient Finish

Gradient

Position of

Peak Force

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How the Target Force Curve looks like?

Solid, front-loaded, full, no “humps” or glitches.

Catch gradient 10% of the Total Angle (11 deg in sculling, 9 deg in rowing);

Position of the Peak Force 33% of Total Angle (down to 30% in 8+ and 4x, up to 38% in 1x);

Finish gradient 32% (up to 36% in big boats, down to 26% in small boats).

0%

20%

40%

60%

80%

100%

0% 20% 40% 60% 80% 100%

Norm.Oar Angle (deg)

Normalized Force (% of Max.)

70% of Max.Force

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How can we present the Force Curve?

Force vs. time (s) is good for

synchronisation with other

variables, but difficult to

compare at various stroke

rates;

Force vs. time (% of stroke

cycle) is another option;

Force vs. Oar Angle allows

easy comparison at various

stroke rates and useful for

defining position of specific

points (peaks, gaps).

-100

0

100

200

300

400

500

600

700

800

0.0 0.5 1.0 1.5 2.0 2.5

212529333739

Time (s)

Handle Force (N) Stroke Rate (1/min)

-100

0

100

200

300

400

500

600

700

800

0% 20% 40% 60% 80% 100%

212529333739

Time (% of cycle)

Handle Force (N) Stroke Rate (1/min)

-100

0

100

200

300

400

500

600

700

800

-75 -50 -25 0 25 50

21

25

29

33

37

39

Oar Angle (deg)

Handle Force (N) Stroke Rate (1/min)

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Why the stretcher force is positive?

1. Drive phase must be emphasised, because

the system velocity increases only during the

drive;

2. During the drive, acceleration of the rower’s

mass must be emphasised, because it is the

main “accumulator” of the kinetic energy;

3. The stretcher force must be emphasised,

because this is the only force, which

accelerated the rower’s centre of mass;

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Why accelerate the rower’s mass during the drive?

Kinetic energy of the system

increases ONLY during the

drive phase;

Kinetic energy of the system

decreases during the recovery

phase and we can not change

it;

Amount of kinetic energy, which

the system gained during the

drive phase, determines

average velocity of the system;

Rower’s mass is the main

“accumulator” of the kinetic

energy;

0

500

1000

1500

2000

2500

3000

Rowers

Boat

System

Drive

Kinetic Energy (J)

T (s)

D boat

D rowers

Ek = (m v2) / 2

Steve Fairbairn (1930):

“Find out how to use your

weight and you will have

solved the problem of how

to move the boat”

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Power transfer though the stretcher

In rowing the power is transferred through BOTH

handle and stretcher in the proportion about

60/40%

Squat: power transfer through upper body only

Legs press: power transfer through the foot-stretcher only

P = F * v

23Analogy with canoeing makes it easier to

understand why the stretcher force is important

Action Forces

Reaction Forces

Centre

of Mass

Force

Transfer

1. Athlete apply

action forces

2. Action forces

create opposite

reaction forces

3. Reaction forces

move centres of mass

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How blade propulsive efficiency is defined?

Propulsive Power

P propulsive = F V mass centre

F

Vm.c.Vm.c.

F

Eblade = P propulsive / P total = (P - P waste) / P

Waste Power

F

V

P waste = F V

F V

25

Handle

Pin

Blade

DriveRecoveryRecovery

Oar Track during stroke cycle

26

What we need to know about blade efficiency?

Hydro-lift force works at sharp angles of attack and contributes 56% of the blade propulsive force;

Drag force works at the middle of the drive and contributes 44% of the blade propulsive force.

How can we increase the blade propulsive efficiency?

Use bigger blade area;

Use heavier gearing;

Utilise hydro-lift effect -> apply more

force at sharp oar angles at catch;

Place the blade at the optimal depth

under the water (4-6 deg).70%

80%

90%

100%

-75 -50 -25 0 25 50

Blade

Efficiency (%)

Oar Angle (deg)

50

100

150

Flift

Fdrag

Fblade total

Force (N)

30

60

90

Angle of attack (deg)

1

2

3

4

5

Vblade

Vboat

Velocity (m/s)

27

Oar blade as a jet engine? At the start of runway, the

efficiency of a jet plane is zero, because its velocity is zero, but the thrust and specific impulse are maximal.

As the plane accelerates, its efficiency increases, and became 100%, if the plane speed is equal to the speed of exhaust gasesExhaust Speed

Propulsion

Isp = (Vg – V) m / t

E= 2 / (1 + Vg / V)

28Specific Impulse as a measure of the blade

performance?

The specific impulse can be used together with blade efficiency for evaluation of the blade work.

A higher specific impulse is generated at a lighter gearing ratio, but at a lower handle velocity at the same time.

This could be achieved either by using bigger blade area, or by more effective thrust production using a better shape and/or utilisation of hydro lift effect.

Power (W)

0

500

1000

1500

0

100

200

300

Thrust

Force (N)

Oar Angle

(deg)

0.1

0.2

-75 -50 -25 0 50

Blade specific impulse

Isp (s/m)

25

1

2

3

-1

1

2

-5

0

5

10Handle

Velocity

Vert.angle

Isp = Ftrust / Prow

Isp = (Lin / Lout) cos(α) / Vh

29

How we analyze rower’s blade work?

Two-dimensional (2D) sensor measures oar angles horizontal and vertical planes, which allows to define a path of the blade relative to water.

Criterion -3 deg was chosen to indicate full immersion of the blade into the water.

- 6

0

3

- 50 - 25

Vertical Angle (deg)

Catch Slip

Release Slip

Water Level

Recovery

Effective Angle

Catch Finish

3

Drive

Target Curve

Horizontal Angle (deg)

30

Rotational motions of the oar.

Rotational motions of the oar were measured with BioRow 7Dwireless sensor;

The most understandable and informative measured variable appeared to be the roll Gx, which is clearly related to the squaring-feathering of the oar.

Angular

Velocities

+ -

Roll

Pitch

+-

Yaw

+

Gx

Gy

Gz+Ay

+Ax

+Az

Accelerations

-10

-5

0

5

Ax

Ay

Az

Oar Accelerations (m/s2)

Catch

Finish

-200

0

200

400

600

0.0 0.5 1.0 1.5 2.0

Gx

Gy

Gz

Oar Rotations

(deg/s)

Drive0

100

200

300

0.0 0.5 1.0 1.5

-5

0

5

Force

Vertical AngleForce (N)

Time (s)

2

1

3

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When the blade squared – feathered?

The squaring takes 0.25-

0.35s and completed at the

catch, when the oar change

direction, but the blade is still

in the air.

The feathering began, when

the centre of the blade

crosses the water level and

completed in about 0.15-

0.25s – faster than squaring;

The higher the stroke rate,

the longer distance of

recovery is required to square

the blade.

-400

-200

0

200

400

600

-75 -50 -25 0 25 50

20.430.0

35.037.0

Oar Roll Velocity Gx (deg/s)

Stroke

Rate

Catch Finish

Drive

Recovery

0

20

40

60

80

-75 -50 -25 0 50Oar Angle (deg)

Oar Roll

Angle

(deg)

SquaringFeathering

-0.5

0.5

-2.0 -1.0 0.0 1.0

Horizontal Position (m)

Vertical

Position (m)Water level

Catch slipFinish slip

Squaring

With BioRowTel system, the oar roll

data in conjunction with horizontal and

vertical oar angles allows a full

reconstruction of the oar movements

relative to the water level.

32

Determination of “Boat velocity efficiency”

The main reasons for energy losses are:

•boat velocity fluctuation;

•non-linear dependence of drug power on velocity

Pdrag = k V3

Propulsive power

Drag Power

Boat Velocity

Drag Power

V

F

P = kV3

F = kV2

33

Boat speed during recovery The hull speed increases

through recovery at higher stroke rates.

The higher the rate, the closer the peak speed to the catch.

The reason for this is in interaction of the rower’s and the boat masses.

The transmission of the kinetic energy from the rower’s mass is to the hull occurs during recovery by means of pull through the foot-stretcher.

At the higher rating the pull force exceeds 200N and overcomes the drag force ≈100N at the hull.

-1.5

-1.0

-0.5

0.0

0.5

1.0

20

26

30

35

37

Angle

Hull velocity rel. average (m/s)

CatchDrive

Release

Recovery

-400

-200

0

200

400

600

800

1000

20

26

30

35

37

Foot-stretcher Force (N)

ReleaseCatch

Drive

Recovery

Angle

-2

-1

0

1

HullRower CMSystem CM

Velocity rel. Average (m/s) Rate 37

Release

Catch

Drive

RecoveryRecovery

34Variations of the boat velocity is NOT the

main reason of the energy losses in rowingThere are two main reasons

of the variation of the boat velocity:

Periodical production of the propulsive force;

Movement of the rower’s mass relative to the boat shell.

We can not change these factors without changing the nature of rowing

Increase of the boat velocity during recovery caused by transfer of KINETIC ENERGY from the rower’s mass to the boat.

-6

-4

-2

0

2

4

RowerBoatSystem

Accelerations (m/sTime

0

200

400

600

Force (N)

Catch Release

Recovery Drive Recovery

-2

-1

0

1

BoatRower CMSystem CM

Velocity rel. Average (m/s)

Release

Catch

Drive

RecoveryRecovery

Time

Time

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How can we help to optimize rigging?

Rigging Calculator www.biorow.com/RigChart.aspx

www.biorow.com

35

Thanks to Ian Wilson of Concept2 UK for the idea and

Dick & Peter Dreissigacker of Concept 2 for support.

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What we can measure in rigging?Why rigging is important?

Oar dimensions define

gearing, which determines

force/velocity ratio of

rower’s muscles

contraction;

Stretcher position is

related to ratio of

catch/finish angles;

Gate height and blade

pitch defines vertical oar

angles;

Stretcher angle and

height defines lift force and

kinetics of the drive.www.biorow.com

36

Spread (sweep)

Gate Height

Height from water

Heels Depth

Span (sculling)

Overlap (sculling)

Overlap (Sweep)

Stretcher

Angle

Work through

Pitch

Seat Travel

Gate Height

Stretcher position

SlidesAngle

37

What is correct definition of the Gearing?

The standard definition of the

gearing is the ratio of

velocities (or displacements,

travels) of output to input;

In rowing, velocity of the

output is defined by actual

outboard, input – by actual

inboard;

The span/spread does NOT

affect gearing;

Blade efficiency or “slippage”

DOES affect Gearing.

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37

Gearing = Actual Outboard / Actual Inboard

= (Out.-SL/2- SW/2) / (Inb.-Hnd/2+SW/2)

Blade Travel

Handle Travel

Oar LengthInboard

PinActual Inboard

Oar LengthInboard

Actual OutboardPin

38

Is gearing constant during the drive?

At sharp oar angles only part of

blade velocity is parallel to the

boat velocity;

Effect of the oar angle is small

until 45deg;

Gearing ratio became twice

heavier at the oar angle 60deg;

Gearing ratio became three

times heavier at the oar angle

70deg;

Gearing ratio became six times

heavier at the oar angle 80deg;

The most common catch angles

are between 55deg (sweep)

and 70deg (sculling).

0

1

2

3

4

5

6

7

8

9

10

11

12

0 10 20 30 40 50 60 70 80

Dynamic Gearing Ratio

(Outboard/Inboard)

Oar Angle (deg)

G(a) = G/cos(a)

Handle Velocity

Blade Velocity

Boat Velocity

39

1987

1988

1992

2001

2011

Our history force measurements in rowing

1998

Instrumented gates

Oar bend sensors

Handle

Oar Shaft Insert

Strain Gauges

“+” “-“

2002

2005

Stretcher

Force

sensors

2001

2005

Seat Force

sensor 2002

2005

2012

2011 Wireless

40

What is measured with force transducers?

Handle Force gives the most accurate power measures, but require calibration of every oar.

Gate force require inboard for power calculation, which could vary during the drive ±5%;

Pin Force is affected by oar angle and axial force, so power could me measured with ±20% accuracy.

Peach Inn. Ltd.

Our gates,

WEBA gate

Handle

Force

Our sensors, FES sensor

Pin Force Gate

Force

Axial Force

41

What Biomechanical Tools we use? BioRowTel v4.5 telemetry system

was created by rowing scientist

for research purposes. It is

accurate, flexible, scalable, based

on “screening” concept, quick to

setup, light;

Scalable design: one “Master”

unit + up to 8 “Slaves”;

Master unit contains:

GPS and impeller input for boat

speed;

3D accelerometer, 3D gyro;

Wind speed & direction input;

Sampling frequency 25-100 Hz;

Resolution 14 bit;

Works >8 hours;

Weight 300g.www.biorow.com

41

“Master” unit “Slave” unit

42

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42

Thank you for attention

Dr. Valery Kleshnev

Rowing Scientist

e-mail: kleval@btinternet.com

Rowing Biomechanics Newsletter www.biorow.com

www.biorow.org