Energy & Power Efficiency ...
Human muscular activity is similar to mechanical systems such as the internal combustion engine in that optimum power efficiency and optimum energy efficiency do not coincide at the same rate of work. To drive a car from one town to another as power efficiently as possible means as fast as possible. All the gears are used and maximum acceleration is employed to reduce the time taken. Fuel consumption is high. To drive the same car as energy efficiently as possible between the same two towns requires a different driving technique aimed at using as little fuel as possible. This distinction between power and energy efficiency also applies to human muscle but seems to have been ignored in discussions of paddling mechanics e.g. Edwards 1987, Sharp 1986, and the term ‘efficiency’ can thus sometimes be used ambiguously.
While it is easy to measure energy efficiency with accuracy in mechanical engines it is much more difficult in biological systems. One study in bicycle ergonomics concluded that human muscle operates at optimum energy efficiency over a broad range around 50 cycles (contraction/relaxation periods) per minute with a small drop in efficiency down to 33 or up to 70 cycles per minute (Whitt & Wilson 1988). In contrast, human muscle maximum power efficiency (easier to measure) was found to occur at around 80 to 90 cycles per minute. E Greenland Inuit kayakers using narrow blades have been observed to paddle at around 60 strokes per minute using a short sliding stroke. Holding the same short sliding stroke paddle without sliding it, would raise the stroke rate to the order of 80 to 90 strokes per minute or more. Thus, the short sliding stroke paddle is ideally suited to the dual needs of hunting, both when cruising to reach an area and also when sprinting in chasing game.
Wooden paddles are also buoyant, unlike many European blades, so that some or all of the weight of the paddle is supported by the water while stroking (Gronseth 1992).
Another feature, which reduces energy required, is the amount of water lifted by the blade when it exits the water at the end of a stroke. If even only a small amount of water is lifted – say 50 grammes – that has to be put in perspective when it is possible to accumulate twenty thousand strokes in a long day’s journey. The 50 grammes adds up to100 Kgs lifted perhaps 30 to 40 cm. Lifted water also falls back, making an unwanted splash that could alert game, an obvious disadvantage to Inuit hunters.
Muscle efficiency is only one component of the system involving the propulsion of a kayak. In still water, with no wind, the kayak itself (length and beam dimensions mainly), and the weight, muscular strength and fitness of the paddler are some of the variables which would make it very difficult to measure differences in energy efficiency between Inuit narrow blades and European wide blades.
Traditionally the Inuit paddle was made for each paddler and the width of the loom was adjusted to equal the distance between the bases of the thumbs when the hands are allowed to hang naturally at the sides. This is about the same as the width of the shoulders. A narrow distance between the hands means that each hand is lifted the minimum height when stroking. This represents a considerable energy saving compared to the contemporary European fashion for a wider than shoulder grip with wide-bladed paddles. Standard (British Canoe Union) teaching advocates a wide grip where the forearms are held vertical and the upper arms horizontal (Train, 1990). This is because the wider grip is required for power efficiency in stroking with European paddles, necessary in fast rivers and surf. If a touring kayaker paddles at 50 strokes per minute for a long day of, say, ten hours that represents lifting and lowering the arms perhaps 30,000 times. How much they are lifted by therefore becomes important if longer journeys are undertaken.
The narrow blade Inuit paddle, used in a low swinging style from the shoulder, represents an important saving in energy by avoiding the higher arm lift of the European style. This low angle stroking style is made easier since the Inuit blade is narrow and the torsion forces low.
- from: Sea Blades: Fashion or Function? (2001) © Peter Lamont, Isle of Luing, Scotland.
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