Biomechanics Of Rowing

Biomechanics Of Rowing

(Written by Sam Evans)
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Introduction

The role of biomechanics in sport can never be underestimated as an essential tool for analysing and improving the techniques used by the athlete. By breaking down the movement into segments and analysing these parts separately. Each component of the movement and the technique required can be identified and analysed.

Faults can be identified and corrected, however a coach must have a working knowledge of the forces around the joints involved in kinetic motion. Additionally they need to be aware of extrinsic factors that can contribute to impaired performance, friction caused by air or water for instance.

The aim of this assignment is to analyse rowing and in particular the stroke of an oar during the drive phase. With the objective of understanding the biomechanical requirements of executing the skill efficiently and reducing injury risk.

External Biomechanical Factors of Rowing

Propulsion

To move the boat force must be applied. A boat is moved by the action/reaction principle of Newton’s 3rd Law. The oar moves the water one way and the boat moves in the opposite way. The momentum (=mass x velocity) put into the water will be equal and opposite to that acquired by the boat.  This is shown in the diagram below.

Diagram taken from www-atm.atm.ox.ac.uk/rowing/physics.html/basics.html

Resistance

There are various resistive forces that affect the movement of the boat, these are known as drag and there are various types of drag.

  • Skin Drag- is the friction between the rowing shell and the water.
  • Form Drag- is the turbulence of the hull cutting through the water and is determined by the shape of the hull.
  • Wake drag- is the force needed to create the wake as the boat is propelled forward.

www-atm.atm.ox.ac.uk/rowing/physics.html/basics.html and classnotes.

Skin drag is proportional to the texture of the surface of the boat, if a boat for instance was not smooth and had many protrusions the skin drag would be more significant than a smooth polished surface.

Form drag is affected by the shape of the boat, the bow is pointed to give a more streamlined hydrodynamic shape, which will cut through the water. The stern is also tapered to reduce drag.

This shape will not only reduce form drag but will also minimise wake drag as it reduces the water being pushed forward, the length and width of the boat is also a factor within this, the longer and thinner the boat the less wake drag.  Class Notes

Rowers and coaches alike will benefit from understanding drag. Skin and form drag is also affected by the velocity of the boat. If a boats velocity doubles the skin and form drag increase to the square of a boats velocity thus as velocity doubles the skin and form drag quadruples. Dudhia (2008) explains this with more accuracy:

“Racing shells are unusual in that Skin Drag is the major source of resistance (about 80%). For most other craft Wave Drag dominates. Air also contributes to the total drag in similar ways (air is just another fluid). While the contribution from still air is only a few % of the water resistance, air velocity is much more variable, so the contribution can rise to 10s of % in strong head winds.

Skin Drag is proportional to the square of the velocity, so assuming that the Skin Drag dominates, the total resistance R can be written as

(2.1) R = a.v2

where v2 is the square of the velocity and a is some constant depending on the wetted surface area and hull shape (i.e. remains the same for a given boat and crew).

To maintain a constant velocity, the force applied must equal the resistance so there is no net acceleration or deceleration (Newton’s 1st Law, actually, just to complete the set). Hence the average power P required (=force x velocity) is

(2.2) P = a.v3

This means that to double the boat speed, you need to supply 23 = 8 times more power. Put another way, if you double the power, you only go 1.26 (=21/3) times as fast.”

Dudhia (2008) www-atm.atm.ox.ac.uk/rowing/physics.html/basics.html

Diagram taken from British Journal of Sports Medicine 2002;36:396-402

The above diagram shows the drag forces that affect the boat.

Forces that Affect the Oar

The oar is a fundamental part of rowing in that it transmits the force applied by the rower into moving the boat; this is explained by Baudouin and Hawkins (2002) below:

 “The oar plays an important role in the rowing system by transmitting the force developed by the rower to the blade. Joint moments generated by the rower result in movement of the rower with respect to the shell. This causes a corresponding movement of the oar handle that is resisted by the interaction of the blade and the water. The motion of the oar is partially constrained by the oarlock, restraining the oar from sliding axially.” Baudouin and Hawkins (2002) pg 396

An oar is classed as a second class lever in that the force is applied on the same side. The diagram below shows the forces acting on the oar in a horizontal plane.

Diagram taken from British Journal of Sports Medicine 2002;36:396-402

As this diagram demonstrates Fh and Fb are on both sides of the blade with the pivot point being F0.  Garr G (1997) explains this as:

“in rowing when a blade of an oar catches the water the water acts as a temporary shifting axis and the resistance occurs at the oarlocks”  Gar (1997)

There are many other factors that need to be considered with oar choice and set up, i.e. what length of oar, how much inboard/outboard and blade type should all be considered but for the purposes of this assignment they being ignored.

It should be noted that these are not all the extrinsic biomechanical factors that need to be considered, but for simplicity of this assignment factors such as centre of mass, speed variation, momentum, gearing, balance, foot stretcher positioning and buoyancy are to be ignored.

The Stroke

 The diagram below shows the parts of the stroke as it drives through the water. The intrinsic factors required to execute this stroke will be analysed.

Diagram taken from British Journal of Sports Medicine 2002;36:396-402

The muscle requirements have been analyzed by Dr. Thomas Mazzone (1988). The rowing action has been divided into the following sequence:

  1. The Catch
  2. The Drive
    • Leg emphasis
    • Body swing emphasis
    • Arm pull through emphasis
  3. The Finish
  4. The Recovery

Mazzone (1988)

  

The Catch

Joint Movement Muscles
Knee Flexion Hamstings gastrocnemius, and quads although should be noted rectus femoris is allowing hip flexion.
Hip Flexion Psoas major and minor, iliacus.Rectus femoris contributes to this
Ankles Dorsi flexion       Tibialis anterior
Elbow Extention Triceps Brachii
Shoulder Stabilization Deltoid and trapezius

Mazzone (1988)

It should be noted that in long boat rowing the knees are not as flexed during the catch part of the stroke, nor are the ankles as dorsiflexed but the back is more flexed in this position.

The Drive (leg emphasis)

Joint Movement Muscles
Knee Extends Quadriceps
Hip Extends Hamstrings and gluteus
Feet Planter flexion Soleus and gastrocnemius
Back Stabilization Erecter spinae
Shoulder Contraction Deltoid, supra and ifraspinatus, subscapularis, teres major and minor, biceps brachii
Scapula Stabilization Serratus anterior and trapezius

Mazzone (1988)

The Drive (Body Swing Emphasis)

Joint Movement Muscles
Knee Extension Quadriceps
Hip Extension Hamstrings and gluteus
Back Extension Erecter spinae
Elbow Extension Biceps, barachialis and brachioracialis
Scapula Stabilization Serratus anterior and trapezius

Mazzone (1988)

The Drive (Arm Pull Through Emphasis)

Joint Movement Muscles
Knee  Maximal Extension Quadriceps
Hip Extension Hamstrings and gluteus
Ankles Planter flexion Soleus and gastrocnemius
Back Extension Erecter spinae
Shoulder Full force contraction Deltoid, supra and ifraspinatus, subscapularis, teres major and minor, biceps brachii
Upper arm Rotation Latissimus dorsi, pertoralis major.
Elbow Flexion Elbow flexors
Forearm Stabilization and adduction Flexer and extensor muscles
Scapula Rotated downwards Petoralis minor
Scapula Drawn backwards Trapezius and rhomboid.

Mazzone (1988)

The finish

Joint Movement Muscles
Knee  Maximal Extension Quadriceps
Hip Extension Hamstrings and gluteus
Ankles Planter flexion Soleus and gastrocnemius
Back Extension Erecter spinae
Shoulder Contraction Deltoid, supra and ifraspinatus, subscapularis, teres major and minor, biceps brachii
Upper arm Internal Rotation Latissimus dorsi, pertoralis major.
Elbow Extension Triceps
Forearm Stabilization and adduction Flexer and extensor muscles
Scapula Rotated downwards Petoralis minor
Scapula Drawn backwards Trapezius and rhomboid.

Mazzone (1988)

All diagrams of rower taken from www.concept2.com

Task 2

A Deterministic Biomechanical Model of Rowing Performance taken from  Sports Medicine:Volume 34(12)2004pp 825-848

As Soper and Hume (2004) demonstrate with their deterministic biomechanical model of rowing performance above there are many biomechanical factors that will affect performance.

For the purposes of this assignment stoke length and power application within the stroke will be evaluated briefly with focus on the catch as this has been determined as a cause of lower back pain in rowers due to the hyperflexion of the spine. Rumbell et all (2005)

Stroke Rate versus Stroke Length

Higher stroke rates and longer strokes will increase boat velocity, however it is difficult to achieve both simultaneously. The subject of whether increased stroke rate or longer strokes produces better performance is much debated throughout the rowing world from the very top elite athletes and coaches to local amateur clubs. There is evidence to support both arguments and it is generally down to coaching preference that the decision is made. Due to the physiological demands of a faster stroke rate, a longer stroke length is usually favoured by longboat rowers.

To coach this longer stroke length the rowers are instructed to reach over their toes with extended arms to produce hyperflexion in the trunk and increase the angle of the oar as it enters the water. At the finish of the stroke rowers are to extend the back to a “2 o clock” position with arms flexed at the elbow. This should produce the longest stroke possible.

Force Application

If a robot was used to row a boat it could apply pressure consistently from the start to finish of the stroke. The hypothetical model of the perfect stroke would look like this:

Picture taken from www.home.hia.no/~stephens/ppstroke.htm

This is obviously not possible in rowing and there are many variations on what is coached within rowing, the main three are: the jumping catch, the big finish and the fat middle. The placement of power within these is shown in the graphs below:

Picture taken from www.home.hia.no/~stephens/ppstroke.htm

Picture taken from www.home.hia.no/~stephens/ppstroke.htm

Force application and where it should be applied throughout the stroke is another widely debated topic, and has been widely studied. Schwanitz (1991) researched boat speed according to power application throughout the stoke supported power emphasis at the beginning of the drive (jumping catch).

“The position of the body in the early part of the drive is similar to that of a weightlifter at the beginning of a lift. Schwanitz interprets this position as allowing for a more synchronous whole-body effort incorporating leg, back and arm muscles.  Emphasis on power at the middle or end of the drive would emphasize more isolated and smaller muscles.”  Cornett (2008) pg 172

Although it is argued by various other biomechanical studies that the oar is not in it most productive angle at the beginning of the stroke. The most productive time to apply force is in the middle of the stroke when the oar is in a 90º angle to the boat (fat middle).  Sanderson (1986)

Kleshnev (1999) argues that if consideration is given to the hydrodynamic drag and associated benefits of maintaining boat velocity then rapid force should applied at the catch and finish, with a longer stroke. (the big finish)

To maintain power at the catch, middle and finish of the stroke consistently would be difficult due to lactic acid accumulation and energy production. Thus a compromise must be made.

The Catch

During their study of rowing injuries Rumball et al (2005) found that little research had been done into this area. They also found that, lower back problems, due to hyperflexion of the catch position, were the most frequent injury suffered by rowers.

These injuries have been researched and numerous factors have been identified; tight hamstrings, incorrect breathing, incorrect positioning, the forces the back is exposed to during the catch and poor core stability are a few.

If a rower has tight hamstrings this may impede their ability to hyperflex correctly.  As Rumball (2005) states:

“It is very possible that if an athlete is unable to move into the proper start position due to tight muscles, something else will compensate, and that may be the location of the resulting pain. For example, tight hamstrings prevent the necessary hip flexion in order to achieve the proper position at the catch. This may result in an increased kyphosis in the spine, likely at the thoracic level, as a compensatory mechanism.” Rumball (2005) pg 538

 In the catch position hyperflexion and twisting forces are at their greatest, the lower back muscles are relaxed in this position, then the oar is placed in the water which puts a huge amount of stress on the spine. Rumball (2005) states that in this position:

“compressive force generated at the lumbar spine has of been estimated to be 4.6-fold the rower’s body mass”. Rumball 2005 pg 539.

 

Several researches have found evidence that breathing pattern play a role in the development of lower back problems. This is explained below;

“Manning et al investigated the effects of inspiring versus expiring during the drive phase of rowing. They found that expiring during the drive results in an increased intra-abdominal pressure (IAP), which might help offset the high levels of shear force and compression observed in the lumbar spine during this phase. IAP may have a protective effect on the spine from the tremendous levels of shear and compression at mid-drive. The compressed position of the rower at the catch prevents maximal IAP by inspiration as contraction of the diaphragm is inhibited. Expiration during the drive allows the lungs to be full at the catch and the IAP to peak”.  Rumball (2005) pg 539

As mentioned above, breathing correctly will help to support the lumbar stability during the catch and drive sections of the stroke. It will also help with overall fitness.

Rumball (2005) and other researchers into this area found that rowers who had a “slumped” position at the catch tended to have higher incidences of back pain and injuries. It is suggested that the back be kept strong and straight throughout the execution of the stroke as with weightlifters. This is difficult with long boat rowing as the hyperextension at the catch is more severe than in sliding seat rowing, thus making a strong straight back extremely difficult to maintain. This can be helped by moving the foot rest further away from the rower allowing more space to flex with a straight back.

Caldwell et al  (2003) conducted a study into the effects of  the repetitive motion on the lumbar flexion and the erector spinae muscle during rowing, their findings concluded that rowers need to achieve a more anterior rotation of the pelvis at the catch position. By rotating the spine anteriorly the amount of lumbar flexion is reduced. Strong hip flexor muscles are required to achieve this as is hamstring flexibility.

Caldwell et al (2003) also advise the strengthening of the deep abdominal stabilisers to prevent the compensatory muscles of the erector spinae, hip flexors and quadratus lumborum from being overused.

All of these studies above still promote the need of being hyperflexed at the point of the catch, although in my humble opinion if force production at the angle of the beginning of the catch is not at its greatest and indeed does not contribute a great amount at all to the overall stroke. Is it possible that a less hyperflexed position with a shorter length of stroke but with a higher stoke rate be an option? It is understood that this may possibly increase problems due to the fact that the back is in the hyperflexed position more frequently. No research evidence can be found to back this up, possibly this is an area for future study.

In conclusion a coach needs to apply the evidence within the current research articles to coaching, not only correct technique during the catch phase of the stroke, due to forces the body is under at this time, but a focus must be placed on training out of the boat factors such as flexibility particularly the hip flexors, core strength training and even correct breathing techniques to keep the back strong and healthy.

Conclusion

It is to be noted that there are many biomechanical factors to be considered in rowing. This assignment only scratches the surface of some of these. The forces that act on the boat can be affected by numerous factors such as mass of rowers, boat design, centre of mass and friction to name a few. My understanding of these has been greatly increased through the research conducted for this assignment.

The biomechanical necessities of executing correct technique to improve performance and reduce injury risk have also been greatly highlighted as has the necessity of flexibility and core stability training, and will in future be utilized within my future coaching of rowing.

Bibliography

Books

 Carr G, Mechanics of Sport, 1997 Human Kinetics USA

Journals

 Baudouin A, Hawkins D, A Biomechanical Review of Factors Affecting Rowing Performance British Journal of Sports Medicine 2002;36:396–402

Caldwell JS, McNair PJ, Williams M. The effects of repetitive motion on lumbar flexion and erector spinae muscle activity in rowers. Journal of  Clinical Biomechanics 2003; 18: 704-11

Cornett J, Bush P, Cummings N, An 8-factor model for evaluating crew race performance International Journal of Sports Science and Engineering

Vol. 02 (2008) No. 03, pp. 169-184

Mazzone T  Kinesiology of the rowing stroke, National Strength and Conditioning Association Journal, Volume 10, Number 2, 1988

Rumball J,Constance M. Lebrun D,Stephen R,Ciacca Di, Orlando K Rowing Injuries.  Journal of Sports Medicine 2005; 35 (6): 537-555 Soper C and Hume P, Towards an Ideal Rowing Technique for PerformanceThe Contributions from Biomechanics,Journal of  Sports Med 2004; 34 (12): 825-848

Websites

www.-atm.atm.ox.ac.uk/rowing/physics.html/basics.html    06/05/09 07.30

www.concept2.com                                                                    06/05/09  09.20

www.home.hia.no/~stephens/ppstroke.htm                          09/05/09  10.00

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