Total Arc vs Effective Arc in rowing
Achieving optimal arc/stroke length is admirable but just how much of that arc is effective? Getting the right length of stroke is only half the battle. If you want the boat to move, then an effective arc is the main game.
In this video, Lachlan explores the concept of effective arc and how it can be applied to enhance your rowing. He also discusses the implications of effective arc when combining different athletes to form crews. 

Video Transcript
So today I'm going to have a look at total arc versus effective arc and what it really means for your rowing and how you can think about your rowing stroke a little bit differently when you're rowing along also a couple of things that can be useful when thinking about matching up taller and shorter athletes
So I've got an empower oar lock here and it's measuring the angle of my blade throughout the stroke and so let's have a look at the angle that it's measuring first so these numbers can make a bit more sense so basically got this is our zero degree mark as calculated by the gate and it's pretty common mark to use as zero degrees and so what it's doing is it's measuring the angle so line that up there line it up with the gate and it's measuring this angle out here so whatever angle that is so let's see it's about 61 degrees there 62
yeah let's say 61 degrees and it also measures my finish angle so if i come through to the finish of the stroke
so it measures the maximum angle the blade got to so it looks like it's just there so remember 61 i just clear that we'll do the same again straight line across here get our angle tool back to here back to the gate and the finish angle so say we're about 39 degrees well 40 degrees so 61 plus 40 is 101 degrees so the measurement it's taking here i haven't got the uh i haven't got the the total arc but i've got the effective arc and i've also got the wash which as you've seen in a previous video is this last little bit here with the power drops below 100 newtons catch slip which is at the catch here
the time it takes from the maximum arc until we get to 100 newtons of pressure on that gate
100 newtons of force on that gate should i say and so it's about that six degrees so if we add all of these up it's 6 plus 14 so that's 20 and 89 so it's 109 degrees from the calculations i had i got 101 degrees but it's still pretty close and as its average of the last couple of strokes it's pretty close to what it should be from this uh this stroke coach and orlock in power or lock combination just looking visually and drawing on this ipad which is you know not exactly accurate so i'd say that we're very close so essentially what we're looking at here is an arc of according to the the gear 109 degrees and that's that's one of the previous two strokes as well so it's quite feasible that we'd be a little bit out on this stroke because this is the current one and the stroke coach is the speed coach is showing the previous two average of the previous two strokes so that aside let's just assume that this is the the stroke it's measured the goal is really to try and get your total arc as close to your effective arc as possible so the total arc being the maximum point where the blade is at the catch through to the maximum point where the blade is at the finish and have it throughout that movement a time when it's above 100 newtons so as i said in previous videos the the rowing power on the gate looks kind of like this and this is our 100 newton line
and then this is our catch slip this area here before it reaches that line and this is our finish wash it's an arbitrary measure the 100 newtons but it's a useful tool for helping working out when the power comes on how quickly get the power on at the catch and how quickly how long you hold that power for before it drops off at the finish all right so let's have a look and see how close we get when we're just looking by eye from above calculating that effective length so let's see where i get connected i'd say i'm connected about there blades are in the water there's starting to be a small bend on the oar so let's measure that straight across
measure the angle from the gate try and work it out from the oar so
probably about there's a bit of a bend in the oar which is what you're after we'll say
about 55 degrees now let's have a look at the finish so connected by 55 degrees
and i reckon the power starts coming off about here just here before i start feathering and extracting the blade so we've got 55 degrees plus about there let's have a look and see what that is
straight across measure the angle
back to the gate 55 degrees plus
28 so 55 plus 28 is 83 degrees and so it's quite feasible this stroke was 83 degrees let's let's play it through and see if our effective length goes down closer to 83 degrees or if our visual calculation isn't quite where it should be
so yeah register is 86 degrees so that's actually pretty close to what the nk unit's showing just visually doing it quite roughly on an ipad so i'd say that nk unit is extremely useful for working out these metrics and it gives you a really good indication of of what you're doing and your effective length versus your uh total arc so one of the main things to remember when thinking about your total arc is if you imagine a shorter athlete having a stroke from say here to here just because they're not as tall as a taller athlete and if they've got the same power they're going to get through that time in the water much much quicker than a taller athlete who's taking a stroke from say here all the way through to here so when you're matching up people with crews it's important to remember that shorter athletes and taller athletes will actually end up doing less less or more work through the water depending on how large their total arc is and even if you've got athletes that are all the same height if someone's getting their catch in quickly and gets a catch in here they're connected early they're going to be doing work and it's going to be a lot harder for them to get through to the finish than someone who say puts their blade in the water around here so it's really important to make sure that if if a crew's timing is out that everyone's actually rowing a full arc everyone's actually rowing rowing the right the right length and especially especially getting the blade in at the catch got to get the blade in the catch as quickly as possible without moving the legs without lifting with the shoulders
because if you get the blade in too late your stroke is going to be a lot shorter your effective arc is going to be a lot shorter you're going to get done a lot quicker and you'll be on to the next stroke betw before the person who's actually doing the most to move the boat has even finished their stroke and they'll feel like they're behind but in reality what's happened is the person who hasn't got their blade in the water and got that large effective effective length effective arc is isn't doing what they should to move the boat whereas the person who's got the blade the water is getting left behind is actually moving that boat a lot quicker doing a lot more to move that boat than the person who finishes early so make sure if someone's feeling left behind that's not because they're say hang around at the catch but make sure they're not the one doing it right and everyone else is doing it wrong and vice versa it's important to understand why someone's out of time and some cases they can be out of time because they're rowing well with long length and the other people are rowing short with poor length poor effective length especially
So I've got an empower oar lock here and it's measuring the angle of my blade throughout the stroke and so let's have a look at the angle that it's measuring first so these numbers can make a bit more sense so basically got this is our zero degree mark as calculated by the gate and it's pretty common mark to use as zero degrees and so what it's doing is it's measuring the angle so line that up there line it up with the gate and it's measuring this angle out here so whatever angle that is so let's see it's about 61 degrees there 62
yeah let's say 61 degrees and it also measures my finish angle so if i come through to the finish of the stroke
so it measures the maximum angle the blade got to so it looks like it's just there so remember 61 i just clear that we'll do the same again straight line across here get our angle tool back to here back to the gate and the finish angle so say we're about 39 degrees well 40 degrees so 61 plus 40 is 101 degrees so the measurement it's taking here i haven't got the uh i haven't got the the total arc but i've got the effective arc and i've also got the wash which as you've seen in a previous video is this last little bit here with the power drops below 100 newtons catch slip which is at the catch here
the time it takes from the maximum arc until we get to 100 newtons of pressure on that gate
100 newtons of force on that gate should i say and so it's about that six degrees so if we add all of these up it's 6 plus 14 so that's 20 and 89 so it's 109 degrees from the calculations i had i got 101 degrees but it's still pretty close and as its average of the last couple of strokes it's pretty close to what it should be from this uh this stroke coach and orlock in power or lock combination just looking visually and drawing on this ipad which is you know not exactly accurate so i'd say that we're very close so essentially what we're looking at here is an arc of according to the the gear 109 degrees and that's that's one of the previous two strokes as well so it's quite feasible that we'd be a little bit out on this stroke because this is the current one and the stroke coach is the speed coach is showing the previous two average of the previous two strokes so that aside let's just assume that this is the the stroke it's measured the goal is really to try and get your total arc as close to your effective arc as possible so the total arc being the maximum point where the blade is at the catch through to the maximum point where the blade is at the finish and have it throughout that movement a time when it's above 100 newtons so as i said in previous videos the the rowing power on the gate looks kind of like this and this is our 100 newton line
and then this is our catch slip this area here before it reaches that line and this is our finish wash it's an arbitrary measure the 100 newtons but it's a useful tool for helping working out when the power comes on how quickly get the power on at the catch and how quickly how long you hold that power for before it drops off at the finish all right so let's have a look and see how close we get when we're just looking by eye from above calculating that effective length so let's see where i get connected i'd say i'm connected about there blades are in the water there's starting to be a small bend on the oar so let's measure that straight across
measure the angle from the gate try and work it out from the oar so
probably about there's a bit of a bend in the oar which is what you're after we'll say
about 55 degrees now let's have a look at the finish so connected by 55 degrees
and i reckon the power starts coming off about here just here before i start feathering and extracting the blade so we've got 55 degrees plus about there let's have a look and see what that is
straight across measure the angle
back to the gate 55 degrees plus
28 so 55 plus 28 is 83 degrees and so it's quite feasible this stroke was 83 degrees let's let's play it through and see if our effective length goes down closer to 83 degrees or if our visual calculation isn't quite where it should be
so yeah register is 86 degrees so that's actually pretty close to what the nk unit's showing just visually doing it quite roughly on an ipad so i'd say that nk unit is extremely useful for working out these metrics and it gives you a really good indication of of what you're doing and your effective length versus your uh total arc so one of the main things to remember when thinking about your total arc is if you imagine a shorter athlete having a stroke from say here to here just because they're not as tall as a taller athlete and if they've got the same power they're going to get through that time in the water much much quicker than a taller athlete who's taking a stroke from say here all the way through to here so when you're matching up people with crews it's important to remember that shorter athletes and taller athletes will actually end up doing less less or more work through the water depending on how large their total arc is and even if you've got athletes that are all the same height if someone's getting their catch in quickly and gets a catch in here they're connected early they're going to be doing work and it's going to be a lot harder for them to get through to the finish than someone who say puts their blade in the water around here so it's really important to make sure that if if a crew's timing is out that everyone's actually rowing a full arc everyone's actually rowing rowing the right the right length and especially especially getting the blade in at the catch got to get the blade in the catch as quickly as possible without moving the legs without lifting with the shoulders
because if you get the blade in too late your stroke is going to be a lot shorter your effective arc is going to be a lot shorter you're going to get done a lot quicker and you'll be on to the next stroke betw before the person who's actually doing the most to move the boat has even finished their stroke and they'll feel like they're behind but in reality what's happened is the person who hasn't got their blade in the water and got that large effective effective length effective arc is isn't doing what they should to move the boat whereas the person who's got the blade the water is getting left behind is actually moving that boat a lot quicker doing a lot more to move that boat than the person who finishes early so make sure if someone's feeling left behind that's not because they're say hang around at the catch but make sure they're not the one doing it right and everyone else is doing it wrong and vice versa it's important to understand why someone's out of time and some cases they can be out of time because they're rowing well with long length and the other people are rowing short with poor length poor effective length especially