Presentation on theme: "150 Years of Rowing Faster! Stephen Seiler PhD FACSM"— Presentation transcript:
1 150 Years of Rowing Faster! Stephen Seiler PhD FACSM Faculty of Health and SportAgder University CollegeKristiansand, NorwayGood afternoon.The nice thing about giving a talk on a narrow topic like this during the afternoon session is that you can be fairly certain who your audience is. So, welcome ACSM rowers!With a title like this, there are a number of different paths one can take. I have chosen to follow this one:
2 Oxford-Cambridge Boat Race Winning Times 1845-2005 This talk will focus on the evolution of rowing performance that isdepicted in the next two slides. Here we see the Oxford Yale boat race results since 1845, when the distance became standardized.
3 FISA Men’s championship 1x Winning Times 1894-2004 At the other end of the rowing boat type spectrum, here is data from the men’s 1x, where world championships have been contested under the organization of the International Rowing Federation FISA, since 1893.Unfortunately, similar data over such a long time frame are not available for women’s rowing, so I apologize for the gender bias in this talk. However, every conclusion I will draw is applicable to both males and females.
4 in average velocity over 150 years of competitive rowing 25-30% increasein average velocity over 150 yearsof competitive rowingWhat are the performance variables andhow have they changed?Two points emerge from the figures I just showed you:Performance improvements have been essentially continuous for 150 years andThe rate of improvement in rowing performance is approximately 2% per decade for men.So, with that historical reference frame, what are the performance variables and how have they changed?How will future improvementsbe achieved?
5 Increase Propulsive Power Decrease Power Losses Decrease Drag Forces on BoatAerobicCapacityImprovedTrainingIncreasedPhysicalDimensionsAnaerobicCapacityIncrease PropulsiveEfficiencyof oar/bladeThe rower wishing to improve his or her velocity over 2000m must 1) increase propulsive power and/or 2) decrease power losses.On the left side of the equation, increasing propulsive power may involve increasing aerobic capacity, increasing anaerobic capacity, or possibly increasing muscular strength. In turn, changes in these characteristics over time in the elite rowing population might be attributable to changes in the physical dimensions of the athletes, and/or changes in training.On the power loss side of the equation, I have chosen to organize power losses in terms of three basic sources of inefficiency in converting mechanical power to boat velocity: 1) drag forces on the boat, 2) inefficiencies at the oar/water connection associated with hydrodynamics and oar design, and 3) ”technical efficiency” which we might summarize as being all those aspects of rowing performance that rowing on an ergometer tells one little, or nothing about.MaximalStrengthImproveTechnicalEfficiency
6 ”Evolutionary Constraints” Race duration ~ 6-8 minutesWeight supported activityOar geometry dictates relatively low cycle frequency and favors large stroke distance to accelerate boatHigh water resistance decelerates boat rapidly between force impulsesLet’s set the stage by establishing the ”evolutionary constraints” if you will that might influence athlete selection.
7 These constraints result in: High selection pressure for height and arm lengthHigh selection pressure for absolute (weight independent) aerobic capacitySignificant selection pressure for muscularstrength and anaerobic capacityThese constraints result in selection pressure for a specific type of athlete:
8 Ned Hanlan ca 1880 173cm 71kg Biglin Brothers ca 1865 180cm? 75-80kg? Here are a number of rowing champions of the period 1860s to 1880s.Ned Halan, the Canadian world champion, was a bit small even for rowers of the day at 173cm and 71 kg. The champion crews the Biglin brothers and Ward Brothers were somewhat larger and probably above average in height for the era, but it seems safe to guess that they were not larger than cm and kgNed Hanlan ca 1880173cm71kgBiglin Brothers ca 1865180cm? 75-80kg?Ward Brothers ca 1865185cm?80+kg?
9 ”Since the 19th century there have been clearly documented secular trends to increasing adult height in most European countries with current rates of 10-30mm/decade.”Since that time, the populations of all ”rowing nations” have become taller and heavier. Cole summarizes a large number of studies and concludes that adult height has increased by 1 to 3 cm per decade for over a century.Cole, T.J. Secular Trends in Growth. Proceedingsof the Nurition Society. 59, , 2000.
10 97th percentile for height in Dutch 21 year-olds And, as these data indicate, the most important thing about a rightward shift in the normal distribution for height from the coach’s perspective is that there will be more unusually tall males and females walking around waiting to be directed to the nearest boathouse.Redrawn after data from Fredriks et al, in Cole, T.J. Secular Trends in Growth.Proceedings of the Nutrition Society. 59, , 2000.
11 Taller Population= Taller Elite Rowers Oxford Crew-2005Average Height: 197cmAverage bodyweight98.3 kgSo our 175 to 185 cm tall champions of the late 19th century have evolved into the 190 to 2m tall elite oarsmen of today. The 19th century champion Ned Hanlan would likely have been confused with the coxwain in this crowd.
12 Scaling problems- Geometry or fractal filling volumes? Based on Geometric scaling:Strength and VO2max will increase in proportion to mass 2/3.BUT, Metabolic rates of organisms scale with mass3/4.See: West, G.B et al A general model for theorigin of allometric scaling laws in biology.Science , 1997.But it is not height that propels the boat, but physical capacity and power.Does physical capacity scale directly with an increase in physical dimensions?Biologists will quickly tell us that it does not. But what is the correct scaling factor?
13 VO2 body mass scaling in elite rowers Relationship between maximaloxygen uptake and body mass for117 Danish rowers(national team candidates)r =A key finding of this study was that VO2 scaled with body massraised to the =.73 power, or close to the 0.75 value predictedby metabolic scalingJensen et al recently put allometric scaling laws to the test in 117 national class rowers from Denmark. The top panel shows absolute VO2 max in liters/min as a function of body mass. The middle panel shows how VO2 max per kg body weight actually goes down with increasing body mass. Finally, the lower panel shows VO2 max scaled with body mass to the 0.73 power in these athletes.These data support the concept of a ¾ power scaling law for the body mass to aerobic capacity relationshipFrom: Jensen, K., Johansen, L, Secher, N.H.Influence of body mass on maximal oxygenuptake: effect of sample size. Eur. J. Appl. Physiol.84: , 2001.
14 Measuring Rowing Specific Physical Capacity Today, we have valid reliable ergometers that allow measurement of physical capacity that is reasonably rowing specific. However, training and measuring rowing capacity off the water is not a recent development.Photo courtesy of Mathijs Hofmijster, Faculty of HumanMovement Sciences, Free University Amsterdam, Netherlands
15 220.127.116.11.Already by 1870 a rowing machine design was presented and numerous rowing simulators and ergometers have appeared over time. However, up until the 60s, no production rowing ergometer was designed to accurately quantify work rate, or power.Because accurate ergometry was lacking, and on water experiments were impractical without telemetry, few studies of rowers and their physical capacity exist prior to the 60s.photos 1-4 from Miller, B. ”The development of rowing equipment”5.
16 The Maximum of Human Power and its Fuel From Observations on the Yale University Crew, Winner of the Olympic Championship, Paris, 1924Crew average:Height: 185 cmWeight: 82 kgI would encourage all of you rowing physiologists out there to buy this classic article from the American Physiological Society. Henderson and Haggard investigated a group of world class performers of the day and highlighted a number of challenges associated with testing high performance athletes that resonate still today.They also described, over 85 years ago, essentially all the rowing performance variables that remain in focus today.This undefeated and quite dominant team averaged 186 cm and 82kg by the way.Henderson, Y and Haggard, H.W. American J. Physiology. 72, , 1925
17 Estimated external work required at racing speed based on: 1. Boat pulling measurements2. Work output on a rowingmachine3. Rowing ergometer VO2measurements (but did not go to max)Estimated an external work requirement of ~6 Calories/min or (assuming 20% efficiency)30 Calories/min energy expenditure.Equals ~ 6 Liter/min O2 costAssumed 4 L/min VO2 max and 2 L/min anaerobic contribution during 6 min race.Henderson and Haggard attacked both sides of the energy balance equation, measuring both drag forces on a loaded boat pulled at racing speeds, and mechanical and metabolic power associated with rowing on a rowing ergometer of their own design that allowed them to quantify work output. It was probably an adaptation of the ergometer shown here, which could not be used to quantify work output. Unfortunately, for a number of reasons, both technical and practical , they did not perform MAXIMAL tests on these athletes and were probably influenced by prevailing views of the day that the maximum oxygen consumption for humans was 4 liters /min.Based on the 6 liter min equivalent oxygen cost they arrived at, and a more reasonable anaerobic contribution of 15% of energy cost, these athletes might have averaged closer to 5 L/min VO2 max.The ergometer of the day had to be redesigned toallow a quantification of work and power.
18 1970s - VO2 max vs boat placement in international regatta Even if we assume 5 liter/min max for the dominant, champion 1924crew, they would have been at the bottom of the international rankings 50 years later, as this team boat VO2 max data compiled by Secher demonstrates.Even with modern equipment, their physical capacity would not have been sufficient for the 1924 gold medalists to number among the top 10 boats in an international final 50 years later, as these data compiled by Niels Secher demonstrate.From Secher NH. Rowing.Physiology of Sports(ed. Reilly et al)pp
19 Jackson, R.C. and N. H. Secher. The aerobic demands of rowing in If we jump forward about 50 years after Henderson and Haggard’s work to 1976, another study on the physical capacity of world class rowers deserves some specific mention.It is not uncommon for exercise physiologists to convince world class athletes to be tested in their laboratory. It IS uncommon when the exercise physiologists ARE the world class athletes being tested!Niels Secher was World Champion in 1970 and Roger Jackson Olympic Champion in Jackson went on to have a distinguished career at the University of Calgary while Professor Secher,coauthor of over nearly 300 research studies remains very active at The Copenhagen Muscle Research Center.This study provided on water oxygen consumption measurements collected at competition boat speeds.One observation made by the authors was that although peak VO2 was the same on the water as during bicycle testing,peak ventilation was lower during the rowing bouts.193 cm, 92 kg 6.23 L/min VO2 cycling. Subject reached 6.1 to 6.4 L/min during repeated testing in different boats.Jackson, R.C. and N. H. Secher.The aerobic demands of rowing intwo Olympic rowers. Med. Sci.Sports Exerc. 8(3): , 1976.This study was unique because 1) on water measurements were madeof champion rowers and, 2) the authors of the paper WERE theChampion rowers (Niels Secher, Denmark and Roger Jackson, Canada)who went on to very successful sport science careers.
20 Aerobic Capacity Developments ? X?■7+ L/minDr. Fred HagermanOhio University?Since 1970 a fair number of studies reporting the physical capacity of elite rowers have been reported. A number of these were performed by Dr. Fred Hagerman, now officially retired from Ohio University, who tested national team rowers for over 3 decades. Measurements before the late 1960s are very scarce. So, in the chart above, yellow points are measured results. The green dot is an attempt at correcting the underestimation of Henderson and Haggerd. And, red dots are educated guesses. What seems reasonable to conclude is that physical capacity of elite rowers has increased dramatically over 150 years due to both size increases AND major increase in training load, as we will soon see.Today elite rowers are characterized by an absolute max between 6 and 7 liters per minute. And, yes there are a few reliable measurements of rowerrs exceeding 7 liters per minute, including a recent world and Olympic champion in the 1x.There is just not muchdata available prior to thelate 60s, so the questionmarks emphasise thatthis is guessing. But thataerobic capacity hasincreased Is clear. Today,isolated 7 liter values VO2 maxvalues have been recorded inseveral good laboratories forchampion rowers.
21 7.5 L/min, 95kg, (do they exist?) 79 ml/kg/min, 270 ml/kg0.73/min ”Typical World Class”XC skiers7.5 L/min, 95kg, (do they exist?)79 ml/kg/min,270 ml/kg0.73/minAllometrically equivalent rower??Living in Scandinavia and being familiar with the testing results of a group of endurance athletes well known for their aerobic capacity, it is tempting to make some comparisons. If we scale up typical international class test results from XC skiers using the 0.73 power scaling factor quantified by Jensen and colleagues, we get an allometrically equivalent 95kg rower with a 7.5 liter VO2 max. While test results of 7 liters/min have been reported, a reputable value of 7.5 L/min has not been reported to my knowledge. Where are these athletes? Why are they so rare?
22 How much of performance improvement is attributable to increased physical dimensions? Based on W Cup resultsfrom Lucerne over:3 years3 boat types1st 3 places2%4%Here I use present day differences in boat velocity for world class lightweight and heavyweight crews to demonstrate that the massive scale up in body size has not resulted in a proportionalincrease in boat speed, due to increased power losses associated with greater boat drag. The difference between these two weight classes today is about the same as the increase in body size observed over 150 yearsIt is clear that we have witnessed a dramatic scale-up of physical dimensions and in turn physical capacity among the best rowers over time. However, how much has this increase in physical dimensions contributed to improved performance, independent of other factors, such as training? Comparing modern lightweight and heavy weight performers gives us a clue. Here I quantified the performance velocity difference for the top 3 finishers from 3 boat classes over 3 years from Lucerne, a venue with generally stable racing conditions. Athletes from these two groups differ in bodyweight and height by an amount quite similar to the difference between elite rowers before the turn of the century and today.
23 yards as fast as possible Rise at 7 a.m: Runyards as fast as possibleAbout 5:30: Start for the river and rowfor the starting post and backBut, of course, not only have physical dimension changed, but both lightweight and HWt rowers train differently today then 150 years ago. This book by British coach Archibald McClaren from 1866 gives us some clues to what state of the art training looked like in the mid to late 19th century.Reckoning a half an hour in rowing to andhalf an hour from the starting point, and aquarter of an hour for the morning run- in all,say, one and a quarter hours.
24 US National Team training during peak loading period Mon8:00Weights120 min10:00Row70 min Steady state in pairsHR4:00100 min Steady state in pairsHRTues2 x 5x5 min ON/1 min OFF in pairsHR10:30Erg12 kilometersHR 150100min Steady state in eightWedRun3 x 10 laps100min steady in eightThurs2 sets 12 x 20 power strokes in eight75 min (about 17500m)3 x 20 minFri15 km3:3090 min steady state in eightSat9:003:0090 min steady state in fourSun3 sets 4 x 4 min ON/1 min OFF in pairsUS National Team training during peak loading period3 sessions/day30+ hr/wkHere is a training description for US national team rowers preparing for the Olympics.From US Women’snational team 1996
25 Developments in training over last 3 decades 924 hrs.yr-1966 hrs.yr-11128 hr.yr-15.8 l.min-16.4 l.min-16.5 l.min-1If we zoom in on training developments over the last few decades, Fiskerstrand and I recently published a retrospective analysisof the training and physical characteristics of 28 international medal winning Norwegian rowers from the 70s, 80s, and 90s. Make note that the average VO2 maxof the athletes increased about half a liter/min form the 70s to the 80s. This was not attributable due to a size increase, as physical dimensions were unchanged.It also does not seem to be well explained by the small increase in training volume.Fiskerstrand A, Seiler KS Training and performance characteristics among Norwegian international rowers Scand J Med Sci Sports (5):
26 Developments in training over last 3 decades There was a significant change in training philosophy from the 1970s that seems to correspond with a better understanding of the energetics of rowing.Specifically, very high intensity training was decreased and more training at lower intensities was added. Notice that the change in training intensity distribution corresponds with the change in physicalcapacity of the rowers.Fiskerstrand A, Seiler KS Training and performance characteristics among Norwegian international rowers Scand J Med Sci Sports (5):
27 1860s - ”Athletes Heart” debate begins 1867- London surgeon F.C. Shey likened The Boat Race to cruelty to animals, warning that maximal effort for 20 minutes could lead to permanent injury.1873- John Morgan (physician and former Oxford crew captain) compared 251 former oarsmen with non-rowers -concluded that the rowers had lived 2 years longer!Myocardial hypertrophy was key topic of debate, but tools for measurement (besides at autopsy) were not yet available.Seen in the context of the training loads endured by modern elite rowers, it is difficult to imagine that the training and competition program described by Archibald McClaren In 1866 was once viewed as potentially hazardous to one’s health, but it was.See: Park, R.J. High Protein Diets, ”Damaged Hearts and Rowing Men: antecendents of Modern Sports Medicine and Exercise Science, Exercise and Sport Science Reviews, 25, , 1997.See also: Thompson P.D. Historical aspects of the Athletes Heart. MSSE 35(2),
28 Big-hearted Italian Rowers - 1980s Of 947 elite Italian athletes tested, 16 had ventricular wall thicknesses exceeding normal criteria for cardiomyopathy. 15 of these 16 were rowers or canoeists (all international medalists).Suggested that combination of pressure and volume loading on heart in rowing was unique,but adaptation was physiological and not pathological.Questions about the athletes heart and a potential connection to cardiomyopathy and sudden cardiac death have continued to the present day.In 1991, Pelicia publiched the results of cardiological screenings of almost 1000 elite Italian athletes. Among them only 16 were found to haveventricular wall thicknesses exceeding clinical standards for hypertrophic cardiomyopathy. Interestingly, most of these were rowers, often highly successful ones.from: Pelliccia A. et al. The upper limit of physiologic cardiac hypertrophyin highly trained elite athletes. New England J. Med. 324, , 1991.
29 elite rower untrained control These ultrasound images show thehypertrophied but geometrically similar heart of an elite Italian rower compared to the smaller heart of an untrained subject.untrained controlPelicia went on in subsequent studies to show that the myocardial remodeling induced by elite level training wasphysiological and not pathological. Here we see a elite rowers heart in the 2 panels above and the heart of an untrained control below.From: Pelliccia et al. Global left ventricular shape is not alteredas a consequence of physiologic remodellingin highly trained athletes. Am. J. Cardiol. 86(6), , 2000
30 Myocardial adaptation to heavy endurance training was shown to be reversed withdetraining.The functional andmorphological changesdescribed as the”Athlete’s Heart” areadaptive, not pathological.In this study, Pelicia showed that the extreme ventricular hypertrophy observed in some eltie endurance athletes wasreversed with long term detraining. More than any other research group, the Italian cardiologists lead by Pelicia have clarified the true nature of the “Athletes heart” first described almost 150 years ago.Pelliccia et al. Remodeling of Left VentricularHypertrophy in Elite Athletes After Long-TermDeconditioning Circulation. 105:944, 2002
31 Force production and strength in rowing Ishiko used strain gauge dynamometers mounted on the oars of the silver medal winning 8+ from Tokyo 1964 to measure peak dynamic forces.Values were of the magnitude N based on the figures shownPhoto from WEBA sport GMBHRowing is often viewed as a sport that bridges strength and endurance. Among endurance sports, rowing is probably the sport where the most attention has been given to the role of muscular strength as a limiting factor in performance.Attempts at measuring forces at the pin were already made at the turn of the century. However, the first useful data was provided by Ishiko collected on Olympic medalists form the 64 Tokyo Olympics.We will come back to another aspect of Ishiko’s force measurement work laterIshiko, T. Application of telemetry to sport activities. Biomechanics.1: , 1967.
32 How Strong do Rowers need to be? 1971 - Secher calculated power to row at winning speed in 1972championships = 450 watts (2749 kpm/min)”In accordance with the force-velocity relationship a minimal (isometric) rowing strength of 53 ÷ 0.4 = 133 kp (1300N) will be essential.”A few years after Ishiko’s work was published, Secher related the average force per stroke to the knownfeatures of the force velocity relationship and assumed that the rowing stroke was performed at about 0.4 times peakcontractile velocity during a race. From this he estimated an isometric strength requirement of 1300N for “Rowing Strength”From: Secher, N.H. Isometric rowing strength ofexperienced and inexperienced oarsmen.Med. Sci. Sports Exerc.7(4) , 1975.
33 Force production and rowing strength Measured isometric force in7 Olympic/world medalists,plus other rowers andnon-rowersAverage peak isometric force(mid-drive): 2000 Nin medalistsSecher than measured 7 Olympic and world medalists on a series of strength tests, including the one pictured which he called a rowing strength test.Lower level rowers and non-rowers were also measured.The 2 interesting findings were:1) The difference in rowing strength between the champion rowers and the club rowers and non rowers was not impressiveand 2) rowing strength was not correlated with strength measures for the different muscle groups involved when measured in isolation. This suggests that typical weight room exercises may transfer poorly to rowing.NO CORRELATIONbetween ”rowing strength”and leg extension, backextension, elbow flexion, etc.From: Secher, N.H. Isometric rowing strength ofexperienced and inexperienced oarsmen.Med. Sci. Sports Exerc.7(4) , 1975.
34 Increase Total Propulsive Power Decrease Power Losses Aerobic Capacity AnaerobicMaximalStrengthPhysicalDimensions?ImprovedTrainingDecreasePowerLossesDrag Forceson BoatIncrease PropulsiveEfficiencyof oar/bladeImproveTechnicalLe us now look to the other side of the power balance equation
35 Decrease Power Losses Decrease Drag Forces on Boat Increase Propulsive Efficiencyof oar/bladeWe begin with the issue of the drag forces acting on the boatImproveTechnicalEfficiency
36 Boat Velocity – Oxygen Demand Relationship This figure shows that achieving a 10% increase in average boat velocitywould require an impossibly large increase in aerobic capacity. Thismeans that any revolutionary boat velocity increases in the future must beachieved by decreasing power losses (boat drag for example).Boat velocityrange for Men’sand women’s 1xIt has long been established that the resistance on a rowing shell moving through the water increases exponentially with velocity. Haggerd and Henderson showed this for rowing shells in their boat pulling studies in 1925.While resistance increases with the square of velocity, power demands increase in proportion to the cube of the velocity change. If we express power demands in terms of oxygen demand the picture looks roughly like this.What we can quickly concede is that any large increase in boat velocity from present levels, say 10%, would require what I would call a “genetically prohibitive” increase in physical capacity of the rowers, using today’s boats.
37 Drag Forces on the Boat and Rower Boat Surface Drag - 80% of hydrodynamic drag (depends on boat shape and total wetted surface area)Wave drag contribution small - <10%of hydrodynamic dragAir resistance – normally <10% of total drag, depends on cross-sectional area of rowers plus shellThere is general agreement that skin drag, or the drag associated with water being dragged along by the surface of the boat as it passes through, represents the major source of drag on rowing shells. Normally wave drag is the largest source of resistance on water craft, but rowing shells have such a large length to beam ratio that wave drag only accounts for about 7% of total drag.Air resistance can be meaningful, but normally only accounts for 10% of total drag. Plus there is just not much that can be won in terms of improving the aerodynamics of the rowing movement or the large rowers performing them.Some have tried.
38 typical of those used in racing prior to 1830 In-rigged wherrytypical of those used in racingprior to 1830Here was the racing standard boat of the day in 1830, an inrigged boat with keel and a “rough” hull construction. The beam of the boat was about 1.1 metersfigures from Miller, B. ”The development of rowing equipment”
39 All radical boat form improvements completed by 1856. Outrigger tried byBrown and Emmet, and perfectedby Harry ClasperKeel-less hull developed by William Pocock and Harry ClasperThin-skin applied to keel-less frameby Matt TaylorOver a 25 year period, rowing boats underwent a metamorphosis, immediately shedding half a meter of width thanks to the invention of the outrigger, lengthening to achieve the present extreme length to beam ratio, removing the keel, and covering an internal frame with a smooth wooden skin.By 1856, the metamorphosis was essentially complete.Small refinements have continued to the present day, but as this picture shows, the 4 man shell built by Matt Taylor in 1855 would be hard to distinguish from a wooden boat 100 years later.From the 1850s there were probably no radical improvements in boat hull design until 1972, when the transition to epoxy and carbon fiber materials resulted in a dramatic reduction in boat weight. For example, the weight of an 8+ went down by 40kg.Transition to epoxy and carbon fiberboats came in Boat weight of8+ reduced by 40kgphoto and timeline from Miller, B. ”The development of rowing equipment”
40 Effect of reduction in Boat Weight on boat velocity ΔV/V = -(1/6) Δ M/MtotalExample: Reducing boat+oar weight from32 to 16kg = 2.4% speed increase for 80 kg19th century rower.This equation derived by Oxford physicist Alex Dudhia is one of several that deal with the impact of dead weight in boat velocity.V= boat velocityM = MassΔV= Change in VelocityΔM= Change in MassFrom: Dudhia, A Physics of Rowing.
41 To achieve a radical reduction in drag forces on current boats, they would haveto be lifted out of the water!So, since the radical changes in boat characteristics already happened 150 years ago, and boat weight has been reduced to a standardized level, the only way to achieve a radical improvement in boat velocity might well be to lift it completely out of the water. Former international kayak paddler and hobby physicist Erling Rasmussen has achieved this with flatwater kayaks. Two hydrofoil wings allow a sufficiently high lift to drag ratio to lift the entire boat out of the water under human power. He calculates that a foil kayak 1x could beat a rowing 8+ over 2000m due to the dramtatic reduction in drag.
42 To run this video, download it to the same directory from (7.4 MB)Video of a hydrofoil kayak with two submerged wings. See
43 Decrease Power Losses Decrease Drag Forces on Boat Increase Propulsive Efficiencyof oar/bladeNow we turn our attention to the link between rower power and boat movement, the oar and its propulsive efficiency.ImproveTechnicalEfficiency
44 Oar movement translates rower power to boat velocity TravelFigure from:Baudouin, A. & Hawkins D.A biomechanical review of factors affecting rowing performance. British J. Sports Med. 36:The distance over which the oar blade acts on the water is obviously a direct function of the distance the hands pull through. To achieve a long powerful stroke you have to be able compress and extend the entire body. A key development in rowing propulsion was therefore the development of the sliding seat. It has been suggested that the idea of the sliding seat happened during a rainy day race when some rowers realized that their reach was extended as they slid slightly on their fixed seat.
45 The first true sliding seat was developed by Babcock in 1857 The first true sliding seat was developed by Babcock in It had a limited run of maybe 30 cm. The proper length of the slide in 1870 was described as 4 to 6 inches, or perhaps 15 cm. The evolution of the sliding seat towards the modern version with ~80 cm run took time to achieve technologically. But, as Babcock himself describes, it also complicated the technique of rowing.
46 The slide properly used is a decided advantage and gain of speed, and only objection to its use is its complication and almost impracticable requirement of skill and unison in the crew, rather than any positive defect in its mechanical theory.J.C. Babcock 1870Clearly the gain in power output overweighed the increased technical demands, and the sliding seat and the mastery of a highly compressed catch and powerful whole body drive became a fundamental characteristic of fast rowing.1876 Centennial Regatta, Philadelphia,Pennsylvania. London Crew winning heat
47 Boat direction Photo from www.concept2.com From: Nolte, V. Die Effektivitat des ruderschlages. 1984in: Nolte, V ed. Rowing Faster. Human Kinetics, 2005So the sliding seat transformed rowing into a whole body endurance sport and lengthened the distance over which handle forces could be maintained. This also changed the behavour of the oar blade in the water.We often describe the catch and drive in rowing in terms of “locking on” to the water at the catch. This implies a solidity in the oar- water interface that is not really there.The oar blade moves through the water WITH the boat movement direction, which has lead to suggestions that hydrodynamic lift plays an important role in boat propulsion. AND, the oar slips backwards through the water. In other words energy is lost to moving water.Boat directionA common conception of the oar blade-water connection is that it issolid, but it is not. Water is moved by the blade. Energy is wasted inmoving water instead of moving the boat as the blade “slips”through the water. Much or oar development is related toimproving blade efficiency and decreasing this power loss. However,the improvement has been gradual, in part due to technologicallimitations in oar construction.Photo from
48 Oar hydrodynamic efficiency- propelling the boat but not the water E hydro = Power applied rower – Power loss moving waterPower applied rowerPower applied = Force Moment at the oar * oar angular velocityOar power loss = blade drag force * blade velocity (slip)The hydrodynamic efficiency can be measured in terms of power applied at the oar handle relative to power loss moving waterAffeld, K., Schichl, Ziemann, A. Assessment of rowing efficiency Int. J. Sports Med. 14 (suppl 1): S39-S41, 1993.
49 Oar Evolution Square loomed scull 1847 ”Coffin” blades 1906 ”Square” and”Coffin” blades1906Macon blade-woodenshaftMacon Blade-carbon fiber shaftCleaver blade –ultra light carbon fiber shaft1991-Much of the evolution of oar shape has been in an effort to reduce the slip of the oar through the water and improve hydrodynamic efficiency. Many of you in the audience are familiar with the transition from Macon blades to the current big blade or cleaver design that took the rowing world by storm in 1991.The idea of the big blade was already patented in the 1870s.
50 ? Big blades found to be 3% more hydrodynamically efficient compared to Macon blade?Subsequent studies quantified what rowers quickly recognized to be a meaningful increase in hydrodynamic efficiency and faster boat speed. It seems reasonable to conclude that oar efficiency has improved incrementally over the last 150 years as technology has permitted changes in blade surface area and shape.Affeld, K., Schichl, Ziemann, A. Assessment of rowing efficiencyInt. J. Sports Med. 14 (suppl 1): S39-S41, 1993.
51 Rower/tinkerer/scientists?- The Dreissigacker Brothers Oar developments continue today. The present focus seems to be centered around taking advantage of lift forces at the start and finish of the drive. Volker Nolte seems to have been the first to describe a role for lift in boat propulsion. However, it is oar manufactorers, particularly the Dreissigacker brothers from the US, who have applied an experimental approach to making better oars that continues today. I like these guys. Though not sport scientists, they have certainly applied science and an experimental mindset to the sport of rowing with great success.All pictures from inexchange for unsolicited and indirectendorsement!
52 Effect of Improved Oars on boat speed? Kleshnev (2002) used instrumented boats and measurement of 21 crews to estimate an 18% energy loss to moving water by bladeData suggests 2-3% gain in boat velocity possible with further optimization of oar efficiency (30-50% of the present ~ 6 % velocity loss to oar blade energy waste)Based on current measurements of oar efficiency, we might se a further gain in boat speed of 2-3% if current power losses to the water were cut by 30-50% with better oar design.
53 Rowing Technique: ”Ergs don’t float” This brings us to the final big variable, rowing technique!
54 Optimize/Synchronize DecreasePowerLossesDecreaseDrag Forceson BoatIncrease PropulsiveEfficiencyof oar/bladeGood rowing technique can be boiled down to 1) minimizing velocity fluctuations, 2) minimizing boat rotations, and 3) optimizing and/or synchronizing force curves.DecreasevelocityfluctuationsMinimizeBoatYaw, Pitch and RollOptimize/SynchronizeForceCurvesImproveTechnicalEfficiency
55 Decreasing Velocity Fluctuations SourcesPulsatile Force applicationReactions to body massacceleration in boatLarger fluctuations require greater propulsive power for same average velocityA rowing shell surges through the water. This is due to both the pulsatile nature of the force application, and the reactions of the boat to rowers’ body mass being accelerated in the boat.Larger fluctuations in boat speed require greater propulsive power for the same average velocity. We don’t want to reduce the peak velocity of the boat, but we try to minimize the rapid velocity reduction occurring during the recovery and early catch.Figure from Affeld et al. Int. J.Sports Med. 14: S39-S41, 1993
56 The Sliding Rigger 1954 Sliding Rigger developed by C.E. Poynter (UK) Idea patented in 1870sFunctional model built in 1950sFurther developed by Volker Nolte and Empacher in early 1980sKolbe won WCs in 1981 with sliding riggerTop 5 1x finalists used sliding rigger in 1982.Outlawed by FISA in 1983.We cant eliminate the power surges in the stroke, but we do try to reduce the negative impact on boat speed of the body sliding into the catch.What if we could essentially eliminate the problem of body movement altogether?1954 Sliding Rigger developedby C.E. Poynter (UK)The sliding rigger was outlawed on the basis of its high cost (an unfairadvantage). This argument would not be true today with modernconstruction methods.From: Miller, B. The development of Rowing Equipment.
57 How much speed could be gained by reducing velocity fluctuations by 50%? Estimated ~5% efficiency loss due to velocity fluctuations (see Sanderson and Martindale (1986) and Kleshnev (2002)Reducing this loss by 50% would result ina gain in boat velocity of ~ 1% or ~4seconds in a 7 minute race.Bringing the sliding rigger back would undoubtedly increase boat speed, perhaps as much as 2% if one includes the impact of decreasing the energy cost of rowing, and perhaps an improvement in boat stabilitySliding rigger effect probably bigger!due to decreased energy cost of rowing andincreased stability (an additional 1%+ ?)
58 Better Boat Balance? 0.3 to 0.5 degrees As Babcock noted already in 1870, moving 90kg body rapidly in very light, very narrow boats can make for a technical challenge. Setting up or balancing the boat plays a fundamental role in optimizing performance. So, the question is how much can this aspect of rowing be improved?Elite level rowers allow a boat roll of 0.3 to 2 degrees during rowing.0.3 to 0.5 degrees50% of variability attributableto differences in rower mass0.3 to 2.0 degrees.Highest variabilitybetween rowers here0.1 to 0.6 degrees.0.5 degrees = 2.5 cmbow movementSmith, R. Boat orientation and skill level in sculling boats. CoachesInformation Service
59 The Rowing Stroke Force Curve- A unique signature ”Oarsmen of a crew try to row in the same manner and they believe that they are doing so. But from the data it may be concluded that this is actually not true.”Finally, we come to the rowing stroke itself and its optimization. The work of Ishiko published in 1971 really laid the foundation for a debate which continues today. Ishiko showed that no two rowers have the same exact force profile, even when they came from an experienced crew. He wrote:From: Ishiko, T. Biomechanics of Rowing. Medicine and Sportvolume 6: Biomechanics II, , Karger, Basel 1971
60 ”A new crew with visible success” A ”Good Crew”Rowers 1 and 2 have very similar force curves, showing that thetiming of blade forces in the two rowers is well matched. Rowers 3 and 4 are quite different from 1 and 2, reaching peak force earlier in their stroke. They are similar to each other though, perhaps explaining their ”visible success”. Rowers 7 and 8 show markedly different stroke force profiles, with rower 7 reaching peak force late in the stroke.”A new crew with visible success”German investigators followed up in 1978 by comparing pairs of 2 rowers rowing together. They pointed out for example the similarity in force curves of the “good pair” on top. However, notice the pair on the bottom. They had been rowing together for a year, and yet their force curves were still fundamentally different. Are great crews “born” in the sense that we find rowers who fit together, or can they be made by reshaping individual force curves?2 juniors with ”only 1 year experiencein the same boat”From Schneider, E., Angst, F. Brandt, J.D. Biomechanicsof rowing. In: Asmussen and Jørgensen eds.Biomechanics VI-B Univ. Park Press, Baltimore, 1978.pp
61 Rowing Together: Synchronizing force curves Fatigue changes the amplitudeof the curve, but not its shape.Changing rowers in the boat did not change the force curves of the other rowers, at least not in the short term.Wing and Woodburn examine the force curves of the bow 4 of an 8 and showed thatthe force curves were stable with fatigue andswitching out a rower had no impact on the force curves of the other rowers in the short term. Other studies have showed some adaptability of the rowing force curve to other rowers, so this issue is debated.From: Wing, A.M. and Woodburn, C. The coordination and consistency of rowers in a racing eight. Journal of Sport Sciences. 13, , 1995
62 Is there an optimal force curve? For a 1x sculler: perhaps yes, one thatbalances hydrodynamic and physiological constraints to create a personal optimum.For a team boat: probably no single optimum exists due to interplay between biomechanical and physiological constraints at individual level.A current focus in rowing science is the optimization of the force curves of a crew. IS there an optimal force curve in rowing?see also: Roth, W et al. Force-time characteristics of the rowing stroke and correspondingphysiological muscle adaptations. Int. J. Sports Med. 14 (suppl 1): S32-S34, 1993
63 Contribution of rowing variables to increased velocity over 150 years Increased PhysicalDimensions - 10%Sliding Seat/Evolved RowingTechnique – 20%ImprovedTraining – 33%In conclusion, here is a best estimate of the relative contribution of different variables to the dramatic improvements in boat velocity we have seen over the first 150 years of modern rowing history.The question is, how much faster can they go?Improved hydrodynamicefficiency of oar – 25%Improved Boat Design/reduced dead weight – 12%This is my best estimate of the relative contribution of the different performance variablesaddressed to the development of boat velocity over 150 years. Future improvements are probably bestachieved by further developments in oar efficiency, and perhaps the return of the sliding rigger!
64 This is Oxford. They won.Thank You!This is Cambridge. They…didn’t.