A discussion about rowing "SPI"

General discussion on Training. How to get better on your erg, how to use your erg to get better at another sport, or anything else about improving your abilities.
User avatar
lancecampeau
6k Poster
Posts: 639
Joined: July 23rd, 2017, 9:48 pm

A discussion about rowing "SPI"

Post by lancecampeau » November 2nd, 2020, 12:49 pm

Here we go again... Another post about SPI (stroke power index)

To start, I made an SPI table based on my personal training targets...
Image

So, what does all this mean?

The short answer is that SPI is a fairly basic calculation... your average watts divided by your average strokes for any given workout.

137w / r25 = SPI 5.48
200w / r20 = SPI 10.0


Now lets be honest here... as a comparison metric from one rower to another the SPI rating is not very useful. As you can see on the chart, the numbers start to break down quickly once your stroke rate drops below r18. An SPI of 28.33? Ummm.... no.

The SPI rating is only really useful for comparing your own personal sessions from one to another... and the numbers are only accurate & useful if you maintain a consistent stroke rate. Variying the stroke rate (I.E. sprinting at the end of the piece or interval) will significantly skew the SPI rating.

The length of the piece will also have a significant impact on the athlete's ability to maintain a particular SPI... Shorter pieces typically will have higher SPI numbers while longer pieces may have lower SPI numbers (not always the case, but more often then not)

Now the chart above is color coded for my personal SPI targets... at 6' and 240 lbs, I routinely land in the SPI 8.25 to SPI 11.75 range. I suggest that a shorter, lightweight rower may find an SPI range of 6.25 to 9.25 more reasonable... conversely, large elite power rowers can routinely sustain SPI numbers of 14.0 or more (which I could only manage for a few hundred meters at best).

The bottom line?

SPI rating is a tool that applies to each individual athlete's physiology and is not really fair as a comparison between rowers.
When used as metric for measuring session consistency, I have found the SPI rating to be a useful benchmark for gauging my performance over time. If you approach the SPI metric in this light, it could be useful for your training program as well.

Here is a chart without color for you to map your personal SPI ranges.
Image

Any thoughts?
Male, 46, 6ft / 240 lbs, 183cm / 108 kg / Started erging in Jan 2017
Image

User avatar
hjs
Marathon Poster
Posts: 9782
Joined: March 16th, 2006, 3:18 pm
Location: Amstelveen the netherlands

Re: A discussion about rowing "SPI"

Post by hjs » November 2nd, 2020, 1:01 pm

What would be usefull is not just spi, but also pace at a given rate/power combo.

Like you said, spi in itself does not mean much, very good rowers often don’t use super spi, but have a decent stroke while at same time the fitness to rate high. Topguys, often being 6.4/5 and above still mid to high 30 ies. Not spi/stroking power is often the game changer, but rating is.

User avatar
Citroen
SpamTeam
Posts: 7038
Joined: March 16th, 2006, 3:28 pm
Location: A small cave in deepest darkest Basingstoke, UK

Re: A discussion about rowing "SPI"

Post by Citroen » November 2nd, 2020, 1:28 pm

What units do your SPI values have? Is it the late Bob Spenger's inverse square picofarad?

User avatar
hjs
Marathon Poster
Posts: 9782
Joined: March 16th, 2006, 3:18 pm
Location: Amstelveen the netherlands

Re: A discussion about rowing "SPI"

Post by hjs » November 2nd, 2020, 1:37 pm

Citroen wrote:
November 2nd, 2020, 1:28 pm
What units do your SPI values have? Is it the late Bob Spenger's inverse square picofarad?
SP / strokingpower :wink: straight out of Michigan

Nomath
2k Poster
Posts: 231
Joined: November 27th, 2019, 10:49 am

Re: A discussion about rowing "SPI"

Post by Nomath » November 2nd, 2020, 3:34 pm

Citroen wrote:
November 2nd, 2020, 1:28 pm
What units do your SPI values have? Is it the late Bob Spenger's inverse square picofarad?
1 Watt / strokes/min = 1 J/sec * min/stroke = 60 J/stroke = 14.3 cal/stroke = 0.0569 BTU/stroke

Example : 200 W at 25 strokes/min
200/25 W/strokes/min = 480 J/stroke = 114 cal/stroke = 0.46 BTU/stroke
Last edited by Nomath on November 2nd, 2020, 4:29 pm, edited 1 time in total.

User avatar
lancecampeau
6k Poster
Posts: 639
Joined: July 23rd, 2017, 9:48 pm

Re: A discussion about rowing "SPI"

Post by lancecampeau » November 2nd, 2020, 4:22 pm

Citroen wrote:
November 2nd, 2020, 1:28 pm
What units do your SPI values have? Is it the late Bob Spenger's inverse square picofarad?
lol... no. :D

I certainly don't purport to be an expert on the topic of physiology, energy expenditure, efficiency, etc... but as described above, I view the SPI metric as a simple tool for comparing my sessions over time. After 4 years and 4.5 million meters, Its been my observation that a majority of my sessions seem to land in the range of SPI 8.25 to 11.75 and results that fall outside that window are anomalous.

That said, I'm really more curious to hear what ranges other rowers typically fall into... We all saw this rather painful looking session recently...
Tandstad wrote:
October 16th, 2020, 3:10 pm
Friday night power 10k:
Time Meters Pace Watts Cal/Hr S/M
37:57.4 10,000m 1:53.8 237 1115 17
7:53.2 2,000m 1:58.3 211 1027 18
7:41.7 4,000m 1:55.4 228 1083 16
7:34.2 6,000m 1:53.5 239 1122 16
7:29.9 8,000m 1:52.4 246 1146 17
7:18.4 10,000m 1:49.6 266 1214 17
1:53.8/500m is 237.5w / r17 = SPI 13.97 (and that last interval was 15.64).

Now I know that these kinds of SPI ratings are well outside my ability... so my goal with all of this is to have a better understanding of why SPI 8.25 to 11.75 makes sense for me... What are the factors that cause me to fall into this range consistently? Weight? Height? Age? Technique? Conditioning? etc...

Is it possible to quantify these kinds of factors into a more usable data?

I've heard a few people suggest the watts-per-kilo metric as being a more even playing field for smaller rowers... At 108 kilos, should I be performing at higher level...?

HJS brings up another point...
hjs wrote:
November 2nd, 2020, 1:01 pm
What would be usefull is not just spi, but also pace at a given rate/power combo.

Like you said, spi in itself does not mean much, very good rowers often don’t use super spi, but have a decent stroke while at same time the fitness to rate high. Topguys, often being 6.4/5 and above still mid to high 30 ies. Not spi/stroking power is often the game changer, but rating is.
I'd like to explore a way to encompass all of these ideas into a set of simplified / easily digestible graphs.
Male, 46, 6ft / 240 lbs, 183cm / 108 kg / Started erging in Jan 2017
Image

Tandstad
6k Poster
Posts: 797
Joined: May 10th, 2013, 7:00 am

Re: A discussion about rowing "SPI"

Post by Tandstad » November 2nd, 2020, 4:44 pm

lancecampeau wrote:
November 2nd, 2020, 4:22 pm
Citroen wrote:
November 2nd, 2020, 1:28 pm
What units do your SPI values have? Is it the late Bob Spenger's inverse square picofarad?
lol... no. :D

I certainly don't purport to be an expert on the topic of physiology, energy expenditure, efficiency, etc... but as described above, I view the SPI metric as a simple tool for comparing my sessions over time. After 4 years and 4.5 million meters, Its been my observation that a majority of my sessions seem to land in the range of SPI 8.25 to 11.75 and results that fall outside that window are anomalous.

That said, I'm really more curious to hear what ranges other rowers typically fall into... We all saw this rather painful looking session recently...
Tandstad wrote:
October 16th, 2020, 3:10 pm
Friday night power 10k:
Time Meters Pace Watts Cal/Hr S/M
37:57.4 10,000m 1:53.8 237 1115 17
7:53.2 2,000m 1:58.3 211 1027 18
7:41.7 4,000m 1:55.4 228 1083 16
7:34.2 6,000m 1:53.5 239 1122 16
7:29.9 8,000m 1:52.4 246 1146 17
7:18.4 10,000m 1:49.6 266 1214 17
1:53.8/500m is 237.5w / r17 = SPI 13.97 (and that last interval was 15.64).

Now I know that these kinds of SPI ratings are well outside my ability... so my goal with all of this is to have a better understanding of why SPI 8.25 to 11.75 makes sense for me... What are the factors that cause me to fall into this range consistently? Weight? Height? Age? Technique? Conditioning? etc...

Is it possible to quantify these kinds of factors into a more usable data?

I've heard a few people suggest the watts-per-kilo metric as being a more even playing field for smaller rowers... At 108 kilos, should I be performing at higher level...?

HJS brings up another point...
hjs wrote:
November 2nd, 2020, 1:01 pm
What would be usefull is not just spi, but also pace at a given rate/power combo.

Like you said, spi in itself does not mean much, very good rowers often don’t use super spi, but have a decent stroke while at same time the fitness to rate high. Topguys, often being 6.4/5 and above still mid to high 30 ies. Not spi/stroking power is often the game changer, but rating is.
I'd like to explore a way to encompass all of these ideas into a set of simplified / easily digestible graphs.
Cheers for bringing my power workout up Lance, I very much enjoy discussions that could lead to learning something new :) let me know if I can provide any additional data on the table for further investigation. You seem to have a great deal of knowledge, and I am still quite new to the c2 world,(celebrating my 1 year anniversary for picking up the c2 today actually) so I have a lot to learn.

What I can say is that I do not think my technique is very good(obviously it is decent, but I have never investigated how to improve my stroke for instance). I am also not among the strongest(raw lifting power), there are several people on this forum with much better PB's than me in deadlift and squats. I am not very tall(188 cm) for being a erger. On normal sessions I tend to have a stroke length in the mid 140's. During this session I was extending a bit more on the back end of the stroke, and was seeing between 154 and up to a few 160 strokes. Mostly 154 and 157. DF was 135.

The session was never intended to be an all out effort which can be seen at the relatively slow starting pace versus end pace.

I am also an awful(!!) high rater. I blow up immediately if I try to hit rate 40. Even 500 meter intervals are sreldom done at anything higher than 32-34.

PS: Another great low rated achievement lately was Ian Wilde's 6:42.7 2k at rating 19 :lol: completely bananas strong!
35YO, 188 cm, 109 kg, NOR. Instagram: jtands
1K: 2:59(2020), 2K: 6:16(2020), 5K: 16:44(2020), 6K: 20:53(2020), 10K: 34:44(2020), 30min: 8743m(2020), 30r20: 8416(2020), 60min: 16851(2021) HM: 1:16:19.2(2020)

User avatar
hjs
Marathon Poster
Posts: 9782
Joined: March 16th, 2006, 3:18 pm
Location: Amstelveen the netherlands

Re: A discussion about rowing "SPI"

Post by hjs » November 2nd, 2020, 6:32 pm

Re weight versus power. Its not so much about weight itself, but mostly about usefull weight. So higher bodyfat % or not usefull muscle are only dead weight. Not for nothing toprowers are often in the 90kg bracket.
And the very best lightsweights pulled sub 6 at 75kg, and are sub 72 during summer otw.
So only looking at weight is not enough, if you weight 100kg at 25/30% fat, one could easily be 85.

Ps the strongest guy I ever saw pull a fast 2k was, a canoist, from memory 5.47 and 5.49 and did this at rate 25. He was not extremly tall, think 1.90 ish, but bizarre wide. Never seen a man with such broad shoulders. No clue about his weight, but far above 100kg.
Saw him years later, complete changed, a lot less fit, pulled around 6.10 those days.

jamesg
Half Marathon Poster
Posts: 3027
Joined: March 18th, 2006, 3:44 am
Location: Trentino Italy

Re: A discussion about rowing "SPI"

Post by jamesg » November 3rd, 2020, 2:03 am

So, what does all this mean?
That the erg can coach us if we use it's numbers, and so get fit.

One way of using the numbers is via the Work in the stroke, the Topic here, as follows:

On a purely theoretical basis, if weight = 24 H² and force = half this and if Length = height x 0.7, then work per stroke = 8g H³ Nm. Now do it I tell myself. I'm 1.85m, so Work = 8g* x 1.85³ Nm. At rating 20 (per minute) the power would only be 8g x 20/60 x 1.85³ = 26 H³ = 165 W, Work 8. Years ago no prob.

Some hope today, and anyway I've no intention of pulling half my weight (as shown in ergdata, 35 kg average is plenty for me) so I give myself an OAP discount and call it 120-130W and Work 6 to 6.5 on a good day.

Powers for various heights at rating 20 would be as follows. Apply your own age discount (or increase if of exceptional athletic capability):

1.6m - 106W work 5; 1.7m - 128W work 6.4; 1.8m - 151W work 7.5: 1.9m = 180W work 9.
08-1940, 183cm, 84kg. Last seen MHR 155, in 2k (2020-12-03) 8.47.6@23

MartinSH4321
Half Marathon Poster
Posts: 2305
Joined: October 10th, 2018, 6:43 am

Re: A discussion about rowing "SPI"

Post by MartinSH4321 » November 3rd, 2020, 4:06 am

My 2 cents:

A look at the SPI can help to find weaknesses (which are sometimes obvious, but not always). For example: If the pace difference between a 30R20 and a free rate 30' is very low you know fitness is your bottleneck, if the difference is big some strength training can propably help you to improve. Looking at Jo Andre, his stats look pretty balanced, a 30R20 at SPI 14 is very strong and his free rate 30' is still a lot faster.

For 2k+ distances you of course must be strong enough to hold a fast pace at "normal" rating, but fitness is key, you don't need to pull a max SPI 25+ for a sub6 2k.

For sprint distances SPI is very important as raw power is key. If you (as a HW) cant pull an SPI >15 for one single pull you won't get a great 100m result, you can compensate lack of power with rating a bit but higher rating also leads to a lower SPI, you need both to be fast. Chris Scott (100m slides WR holder) regularly posts low rate sprint efforts on instagram where his average SPI is 25-30 for 1' or even 500m :shock:
1983, Austria, 186cm / 100Kg
RHR: 43, MHR: 176
LP: 1:06 100m: 14.0 1': 387m 500m: 1:21.4
1k: 3:05 2k: 6:43 5k: 17:53 30': 8237m 30R20: 8088m 10k: 36:39
60': 16087m, HM: 1:19:42

nick rockliff
10k Poster
Posts: 1096
Joined: March 16th, 2006, 3:54 pm
Location: UK

Re: A discussion about rowing "SPI"

Post by nick rockliff » November 3rd, 2020, 5:02 am

Didn't realise that so many people drilled down into the numbers so much :shock:

After nearly 20 years using the erg and 10s of millions of metres I can honestly say that I've never had the PM display on anything other than pace. I wouldn't have a clue what the watts are for a given pace and it's not really of interest to me.
63 6' 4" 103kg
PBs 2k 6:16.4 5k 16:37.5 10k 34:35.5 30m 8727 60m 17059 HM 74:25.9 FM 2:43:48.8
50s PBs 2k 6.24.3 5k 16.55.4 6k 20.34.2 10k 35.19.0 30m 8633 60m 16685 HM 76.48.7
60s PBs 5k 17.51.2 10k 36.42.6 30m 8263 60m 16089 HM 79.16.6

User avatar
hjs
Marathon Poster
Posts: 9782
Joined: March 16th, 2006, 3:18 pm
Location: Amstelveen the netherlands

Re: A discussion about rowing "SPI"

Post by hjs » November 3rd, 2020, 5:25 am

nick rockliff wrote:
November 3rd, 2020, 5:02 am
Didn't realise that so many people drilled down into the numbers so much :shock:

After nearly 20 years using the erg and 10s of millions of metres I can honestly say that I've never had the PM display on anything other than pace. I wouldn't have a clue what the watts are for a given pace and it's not really of interest to me.
2.30 104 Watt
2.00 200 Watt
1.45 302 Watt
1.35.6 400 Watt
1.28.6 500 Watt

2k Wr 124.0 ish 590 Watt
500 Wr 1.10.5 1000 Watt
1.00.0 flat 1620 Watt
Last edited by hjs on November 3rd, 2020, 5:56 am, edited 1 time in total.

User avatar
max_ratcliffe
10k Poster
Posts: 1297
Joined: May 2nd, 2019, 11:01 pm

Re: A discussion about rowing "SPI"

Post by max_ratcliffe » November 3rd, 2020, 5:40 am

One way I have used SPI lately is for comparing my 1k PB (in June) and 2k PB (October). For the former, I rated 35, for the latter 31, both of which were reasonably in line with my plan, although I had wanted 32 for the 2k.

The surprising thing for me is that the 1k was at an SPI of 9.3, but the 2k was at 8.7, despite the change in rate. Now of course there are more strokes in a 2k than 1k, so extrapolating too far is not helpful (in the limit would you expect to be able to do your max deadlift 200+ times?), but this does suggest to me that I can get a bit quicker by keeping some focus on power rather than simply trying to rate up more.
50 HWT
PBs:
Rower 1'=329m; 500m=1:34.0; 1k=3:25:1; 2k=7:16.5; 5k=19:44; 6k=23:24; 30'=7534m; 10k=40.28; 60'=14621m; HM=1:27:46
SkiErg 1'=298m; 500m=1:42.4; 1k=TBC; 2k=7:43.8; 5k=20:34.8; 6k=TBC; 30'=TBC; 10k=42:50; 60'=TBC; HM=NGTFH

Tandstad
6k Poster
Posts: 797
Joined: May 10th, 2013, 7:00 am

Re: A discussion about rowing "SPI"

Post by Tandstad » November 3rd, 2020, 5:42 am

nick rockliff wrote:
November 3rd, 2020, 5:02 am
Didn't realise that so many people drilled down into the numbers so much :shock:

After nearly 20 years using the erg and 10s of millions of metres I can honestly say that I've never had the PM display on anything other than pace. I wouldn't have a clue what the watts are for a given pace and it's not really of interest to me.
We have to dig into the numbers if we are ever to get close to your all time PB's :D
35YO, 188 cm, 109 kg, NOR. Instagram: jtands
1K: 2:59(2020), 2K: 6:16(2020), 5K: 16:44(2020), 6K: 20:53(2020), 10K: 34:44(2020), 30min: 8743m(2020), 30r20: 8416(2020), 60min: 16851(2021) HM: 1:16:19.2(2020)

MartinSH4321
Half Marathon Poster
Posts: 2305
Joined: October 10th, 2018, 6:43 am

Re: A discussion about rowing "SPI"

Post by MartinSH4321 » November 3rd, 2020, 5:51 am

hjs wrote:
November 3rd, 2020, 5:25 am
nick rockliff wrote:
November 3rd, 2020, 5:02 am
Didn't realise that so many people drilled down into the numbers so much :shock:

After nearly 20 years using the erg and 10s of millions of metres I can honestly say that I've never had the PM display on anything other than pace. I wouldn't have a clue what the watts are for a given pace and it's not really of interest to me.
2.30 104 Watt
2.00 200 Watt
1.45 302 Watt
1.35.6 400 Watt
1.28.6 500 Watt

2k Wr 124.0 ish 590 Watt
500 Wr 1.09.4 1045 Watt
1.00.0 flat 1620 Watt
Little amaendment, the 500 WR is 1:10.5 (1000W), the 1:09.4 is the split for 1' and 432m :wink:
1983, Austria, 186cm / 100Kg
RHR: 43, MHR: 176
LP: 1:06 100m: 14.0 1': 387m 500m: 1:21.4
1k: 3:05 2k: 6:43 5k: 17:53 30': 8237m 30R20: 8088m 10k: 36:39
60': 16087m, HM: 1:19:42

Post Reply