Drag effect!
The difference between a topnotch road bike ($5000-$8000) and an avg. road bike ($500-$800) is mostly weight and a lot of money.
The difference between a rec boats and fitness oriented one is not only weight but also drag; thus, smaller blades won't solve this issue.
In this case, money is not a determinate issue. It is possible to buy preowned ICF boats and/or surskis cheaper than most avg. rec boat.
What a drag! 
Personal observations
Before I bought my ICF kayak, I would take my 64 pound Necky Elaho out on the lake for workouts. I found that my muscles tired easily and it was more of an anerobic workout versus the aerobic workout I get while biking. I also felt like I was going to strain or hurt myself.
Once I started working out with the ICF boat, my muscles were much less fatigued and I could sustain a higher heart rate. Plus, it was just more fun! I can’t seem to sustain as high a heart rate paddling as I do biking. When I bike, my heart rate is somewhere between 150-170. I reach 170 when I push it going up hills on my bike. I’m not sure what my heart rate is while paddling, but I know I don’t sustain that sort of heart rate while paddling my ICF boat for an hour. When I’m racing in a 500 m sprint, my heart does hit my lactate threshold.
My legs are very strong and can easily match my heart’s fitness level. In fact, I don’t get a burn in my legs unless I climb a mountain or purposely mash a larger gear. For me, I think it would be very hard for me to get to the point where my upper body strength will ever match the fitness of my heart.
I think you can get a very good work out from any boat that you paddle. Even if you don’t get a good aerobic workout, you still get a good muscle conditioning workout. Last face, paddling burns much more calories and leads to better health and fitness, then sitting on your couch.
Jamie
Why aren’t you wearing HRM paddling?
Then you would know. Nearly all are waterproof and make good paddling watches.
My heart rate while paddling is pretty close to what it is while cycling - somewhere in the 150s at steady pace (but I’m also overweight and just a casual peddler/paddler). I can’t max it, but can get close and easily get up out of zone in sprints.
My typical leisurely paddles not really pushing it I’ll still average somewhere in the 140s over a 2-3 hours or more including breaks.
Arms may not be able to get HR up as high as legs - but I paddle mostly with core, some leg, and some arm - and together they have no problem giving me a good heart workload - even with my less than optimal core utilization from less than ideal technique and gear.
I alway find it curious when people post saying they can’t get decent aerobic load from paddling. Maybe they’re super fit/runners and my HR’s just elevated from being overweight and in only moderately good shape.
Also depends on purpose of the exercise
I used to race road bikes and trained on my geared race bike (with and without the actual race wheels on it), plus a cheaper, different-frame-geometry fixed gear bike. And I used both types of bikes on rollers as well as outdoors. They ALL helped in my training and the subsequent race results (I won’t bore you with specifics.) But I would never have used a mountain bike for in-season road race training–supplemental activity, yes, but not instead of speed- and smoothness-oriented road training. For one thing, the position and wheel response feel way too different from that of a road racing bike.
But for plain old exercise (not racing)–any bike or biking would be good. Since I no longer race, I pick which bike to use based on mood more than anything else. It’s ALL good exercise.
I view my kayaking the same way. I’m not racing, so for exercise, I’d be happy to paddle a weird variety of kayaks. I sometimes use my Prijon Twister (short, wide, “WW” SOT) for exercise paddling, and despite what some might say, it is good exercise. This boat does not feel as stable as my much narrower SINKs, and it tracks poorly. But on a calm day, I can keep it going straight if I don’t get sloppy. I have paddled it for 15 miles in a group where the other boats were all 19’ long singles and while I had to paddle constantly/steadily just to keep up, there is no question that it was good exercise. Efficient, no.
For building strength, I’d prefer either of my regular sea kayaks. They take longer to get up to speed, but flatwater speed can be noticeably faster. Feels like using a bigger gear, with similar results.
Also, for preparing to do a camping trip, I’d prefer to “train” with my sea kayaks. It’s just a closer match to what is required on such trips than the Twister is.
OTOH, if I’m looking for asymmetries in either my posture or stroke, the Twister will make them clear immediately (assuming a windless day). The other kayaks are affected but not so strongly.
Yanoer, I have thought of asking the same question you did. For many people, there is no good reason to segment “exercise” as belonging solely to speed-oriented kayaks.
hull speed
perhaps the best reason why a short wide boat isn’t a great choice is in the concept of hull speed.
In understanding the concept, the analogy to using bikes no longer is workable.
The real concept of hull speed, simplified, is that, below hull speed, resistance, and by inference, training value, increases linearly with speed. But once hull speed is reached, resistance rises exponentially.
Why is this important? When the resistance goes exponential, it is nearly impossible for most humans to push the boat beyond that speed (if highly skilled, if highly fit, if in a craft capable-ICF sprint- it is done. But that is a lot of ifs). In a shorter boat, that means a limited range of training intensities are available. Work harder, go a bit faster. Work a bit harder, go a bit faster. Work a bit harder… nothing happens except that your heart rate jumps, and the boat goes the same speed. In a longer, narrower boat, there would be far more of those “work a bit harder, go a bit faster” intervals before the wall comes up. Ergo, more training possibilities, especially if one is tuned in to using a heart rate monitor and the use of training zones.
While cyclists do experience wind resistance as speed increases, there is nothing like the limitations of hull speed that a cyclist can experience.
Try it sometime, especially if you have a heart rate monitor. Get into one of those 9.5 foot rec kayaks. Start paddling. Notice how easy it is- at low speeds, these boats are optimized. But notice how little speed increase it takes to suddenly be working a lot harder. Almost sort of “on, off”, for available training intensities.
So, is a shorter boat not good for training? If that is what you got, use it, sitting in that kayak seat is better than sitting in a lounge chair. But if the goal is to get a boat for fitness, it does matter.
karl
Maybe a better question is…
…why a lighter boat? I can understand having a fast design, becuase of all of the reasons mentioned here. But to go with carbon vs kevlar to lose a few lbs isn’t worth the $$ in my opinion. I’d see more sense in losing 5-10 lbs of unnecessary body fat as more effective overall. Although that body fat does come in handy when i flip my surfski this time of year.
Can’t do much work in a short boat
I have a couple shorter boats that I cannot do much work in them. Once I get them up to a certain speed they don’t go any faster and it is really easy to get them up to that hull speed. These boats will go all day long at 3 to 4 mph without any work. A longer boat will let you work harder to go up to 5 or 6 mph.
Heart rate as measurement
I doubt you would ever reach as high a heart rate paddling as you would cycling.
Before using a HR monitor, there are a few things people should know.
The heart and it’s demand-heart rate- is not really the objective in determining training intensity. Using a HR monitor is to gauge indirectly what is going on at the muscular recruitment level.
It used to be done to athletes invasively, by frequent blood tests (ouch! on the fingers). The use of the HR monitor was to try to do something that many could use, without a laboratory.
Functionally, what does this mean? Perhaps an analogy- imagine a car with no tachometer (not hard, as most don’t). For a given task, how hard is the engine working? What if the only way to measure was by the fuel pump flow?
For a given speed, the fuel pump may be putting out a lot, or maybe less.
This is all you know. What you don’t know is, is it a 4 cylinder, or an 8 cylinder. Single driver, or passengers, or towing? From looking at the fuel pump flow only, you wouldn’t know.
So it is with a HR monitor. The HR for a trained athlete, even trained well in two sports, will be different for the same relative intensity. Peak HR will be different, aerobic threshold will be different, anaerobic threshold will be different. The heart is just responding to demand, but the number of muscle groups will change that demand as well as the degree of intensity at the muscular level.
For a rather nice article on HR specific to kayaking, check this out-
www.geocities.com/crazymanwellington/kayaktraining.rtf
karl
One word
CLIMBING.
You can’t tell me you have hard climbs in Florida.
that’s the point
it’s not the thrill of speed but the ability to gauge output by the speed you’re traveling. You could put out huge sprint efforts in a rec boat and you’ll just plow a ditch in the water. With a boat designed for efficiency at higher efforts you can experience differences in speed. The effort is translated to a particular speed effectively.
burning calories
This entire thread has motivated me to make a paddle out of pvc pipe and old tennis or racquetball racquets! Talk about a workout!
I did a 50 mile mtn bike ride in FL.
It kicked my butt! I was like…what mountains…they didn’t have mountains, but they had steep little hills and swampy mud that my bike tires got stuck in. It made for a long day. It took us 8 hours to finish the ride, and I had a new appreciation for off road riding in the flat state of FL!
I’ll probably strap on HRM
when I train this year. I didn’t start wearing the HRM while biking until this winter when I was training for a time trail bike race. My resting heartrate is around 60 so I think I’m pretty fit (for a 40 something woman that could stand to lose a few pounds).
I found when I was training for my sprint boat races last year that I gained weight and it seemed like I actually lost fitness. I attributed this to not biking as much.
Also, one of my club’s sprint coaches recommends cross training in the winter time. He recommends biking or running for an hour three times a week to gain fitness and endurance. ICF Marathon racers will also cross train. They ususally run 6 miles a couple of times a week.
My problem with sprint boat racing is balance. It’s hard to keep a good even pace and maintain my balance. Of course, this will come with more time in the boat.
Sometime this year I plan to buy one of those nice, sleek, light boats and really find out how fast I can go and how high I can get my heart rate up.
fast boats
If you know you’ve got a fast boat then you might be tempted to try longer trips.
Longer trips = more miles = more exercise, simple logic
Cliffjrs - Beamer of rowboats
Actually the beamer of rowboats is a guideboat and its pretty hard to even work up a sweat in one going at hull speed. They only want to go one speed but they do it effortlessly and beautifully.
Stop by when your near central NC and I’d be happy to let you try one.