Intermuscular Coordination: This is the first in a series of forth-coming articles to discuss the benefits of incorporating an air-braked trainer
(an erg) into a cyclists training program. Hunter Allen recently wrote an article on Functional Threshold Power (FTP) and Indoor Training. He outlines various factors that contribute to the usual drop in FTP associated with riding on an indoor trainer.
Here’s an excerpt:
As you ride outside on the road, your bike continues to move forward with momentum from the force that you exerted onto the pedals from roughly the 1 o’clock to 5 o’clock position in the pedal stroke. Across the bottom and top of the pedal stroke, the legs have little ability to create any meaningful force against the pedals because of biomechanical inefficiencies in body position due to being seated almost directly above the crank.
This lack of resistance to pedal against may even give the legs a micro-rest in each pedal stroke as the momentum of the rear wheel continues moving forward and the legs try to keep up with the rpm’s needed to move the crank.
On a rear wheel resistance trainer, there is little to no momentum of the rear wheel. If you stop pedaling the rear wheel comes to an almost immediate stop. Because there is resistance around the entire pedal circle, your legs are not used to having to produce power throughout the entire pedal stroke. As a result of this inefficiency, more strain is put on your cardiovascular system. As a result, this reduces your ability to create the same wattages as outdoors.
Hunter’s article informs us on how to progress as a cyclist.
Indeed, after training on a flywheel-based trainer the legs are not trained to produce power at the top and bottom of the pedal stroke. This is true also for outdoor training when the diet is deficient in extensive climbing. However, the amount of momentum on indoor trainers is in general under-stated. An air-braked trainer such as the Revbox Erg provides an absolute minimum of momentum, the rider is provoked to engage throughout the entire circle to achieve a smooth pedal stroke.
A need to use the muscles that bring the foot through the top and bottom pedal positions is the first step to developing these muscles. It is not enough to simply develop strength in these muscles. For example, a cyclist needs resilient tendons, advanced capillary development, and high mitochondrial density. Even with these developments in place, a cyclist still needs the neuromuscular system developed so that the timing of tension and relaxation is perfect. Anything less than perfect synchrony of neuronal firing spells inefficiency. It takes high-quality, deliberate practice to bring a skill to its highest level. Consistent and well-designed training on an erg goes a long way toward reaching these goals.
One doesn’t generally pedal in a fully engaged fashion when out and about in the world. Rather this skill is needed to develop other skills. Elite cyclists will vary, both consciously and subconsciously, how muscle groups are recruited at any particular moment. For example, a simple shift in position on the saddle results in changing the muscles being recruited. Changing recruitment patterns allows the athlete to rest tired muscles, to work hard after making a hard jump, and to accelerate efficiently during extensive climbs.
The plot (above) comes from data collected while training on the Revbox Erg. Data points are the average power of 2x60s at 100rpm. Rest 2 minutes between. Done, not maximally, rather to complete the warm-up. There’s a 100+ watt gain in 10 days. How? Improved intermuscular and intramuscular coordination. Everything is a skill. One must train from the brain down.
If required the large 580mm diameter fan produces air drag that allows training at power outputs in excess of 2000 watts. In a 53/11 gear ratio, just 50 pedal revolutions per minute, requires an output of 500 watts, making the Revbox Erg an ideal training unit for low cadence strength training. At the top end, 90 RPM in a 53/11 ratio requires 1800 watts and at the low end peddaling with 90 RPM in a 39/28 ratio requires less than 130 watts, which demonstrates the versatility, and resistance range of the Revbox Erg design.
The format of a low friction mechanical connection to the bike via the chain, and the high revolutions of the fan, creates an inertia rate unlike that of any stationary device, and perfect for the specific high power output training demands of the ambitious athlete.
Standard trainer designs have a usable resistance range defined by the mechanical limits of the small diameter units, and exhibit linear resistance increases. An extremely large diameter fan, however, displaces a huge air volume and provides exponential resistance for training across a broad range of parameters. This is a significant part of what makes the Revbox Erg such a brilliant training tool.
The resistance scale provided by the Revbox Erg is suitable for amateur riders through to Tour de France athletes and Olympic track sprinters.
Next to monitoring, and training to, specific power outputs, understanding inertia rates are a critical aspect to improving performance on the bike. A stationary trainer with high inertia only replicates riding on the flat on a smooth road with calm conditions or a tail wind. The Revbox Erg with its deliberately tuned low inertia lightweight air-braked fan encourages increased muscle and motor-skill development at high cadences, as well as providing a very effective means of constant resistance for strength training at low cadences. Developing neuromuscular efficiency, essentially brain to muscle coordination, at high intensities, is crucial to a rider improving the efficiency of oxygen utilization by the working body.
Inertia rates of a stationary trainer have a significant impact on a rider’s pedaling dynamics. Training at carefully chosen pedal speeds and power outputs, certain muscle recruitment is targeted, and results in effective coordination and physiological efficiency gains. The Revbox Erg’s low friction chain connection to the bicycle, enhance the specific inertia characteristics, which make for very stable dynamics at high intensity pedaling loads. This means the resistance unit will not gather momentum at high cadences, nor will it stall at low cadences. This is an ideal environment for the athlete to target exact physiological responses.
To begin to understand the process of forces that produces power, we must consider the laws of physics and how these apply to the bicycle rider. While cadence multiplied by strength equals power, cadence and strength themselves have limits dictated by the riders cardiovascular capacity and efficiency of movement, or coordination.
In basic terms this means a cyclist moves forward by pushing on the pedals for a given time period. (Technically if a rider pushes on the pedals but the bike is prevented from moving forward, and therefore the crankarms do not move, then the rider has produced a force but not work).
Breaking this equation down, if we look at what makes up Work we get:
This means as a rider applies Force (from muscle strength) times Distance (rotation of the crankarms) we get a measure of Work. More Force requires more strength. To produce Power then, a rider applies Force (the leg strength) over a Distance (the crank revolution) to create Work for a period of Time.
(Inertial Mass is the pushing leg and Acceleration is the legs tendency to begin to rotate the crankarm)
Torque is the tendency of a Force to rotate an object about an axis. What this means is that Torque = Force (muscle strength) x Length of lever arm (crankarm in the case of a bicycle).
(Force applied to a crankarm by strength of riders leg) x Rotational Speed (frequency of the applied Torque, high RPM/lower Torque =low RPM/higher Torque) x Time
An endurance rider must be able to maintain a low percentage of their max force to utilise slow twitch muscle fibers to minimise fatigue during the event. If a rider does not have sufficient aerobic capacity or cannot develop sufficient aerobic capacity to main a high cadence (therefore low percentage of max force) then the rider must gain more muscular strength to be able to perform at the required power output. A rider should create a fitness profile of different aspects and limits of their physiological capacity to be able to improve their performance in desired areas as effectively and efficiently as possible. Just performing a standard V02 Max test does not provide in depth enough and adequate enough information to write a training program to result in maximum power output gains.
Inertia is the resistance of any object to a change in its state of motion or rest. This is important because the rotational inertia of a stationary trainer resistance unit has a significant influence on a riders power application and pedaling coordination.
High inertia trainers use heavy rotating units and generally replicate riding on a flat road at low to mid power outputs. They can struggle however, to provide enough resistance at high power outputs. A high inertia trainer only requires force to be applied on the down stroke of the pedal cycle, limiting muscular training benefit. Once the heavy fan or flyweight builds up momentum, the rider has then “topped-out” the trainer, where an increase in pedal speed in the hardest gear does not have any significant effect on resistance.
Virtually any tire-roller type trainer is a low inertia/high friction device. Manufacturers attempt to overcome the friction and add resistance with flyweights. At low pedal speeds the high friction causes a stalling effect through the pedal stroke “dead-center” which forces the rider to employ a compensatory pedaling technique.