Posts tagged “sprint

Physics of Acceleration

Acceleration = (final velocity – initial velocity) / (time at finish – time at start)

Basically, the more you change your speed in a shorter amount of time, the more you have accelerated.  Having a race start that features high acceleration is often a strong deciding factor in races of shorter distance and where the average speed of boats are closely matched.  With the 2017 CDBA Sprint Races just having finished this past weekend, it’s time for teams to start working the long game in prep for more 500m racing fun this summer.

What I wanted to write about regarding acceleration in race starts is to address the wide variation in how teams fiddle with stroke counts and stroke technique in hopes of finding an edge over their competitors.

Many coaches I’ve spoken with over the years often have one of two philosophies about race starts: don’t fix what isn’t broken OR try something different.  The leave-it-be coaches may have strong personal histories of success utilizing a certain race start count and stroke style to the point where the idea of trying something new seems like it would hurt more than help team performance.  That fear is completely understandable, and in certain cases, may be quite accurate.  Think of the novice team trying dragon boat for their first race.  The ‘ole 5-10-10 presents both a great mental and physical challenge with plenty of clacking paddles and drenched partners.  Chances are that coaching different rate ratios and stroke techniques would probably be lost upon such a crew because performance is being limited by base skill.  Now, take the elite paddling crew; each paddler with multiple years of racing experience and a high level of fitness.  If we’re referring to a tight-knit crew with at most 1-2 new additions vs a thrown-together “dream team,” tweaking the start might also be a waste of time because the crew has perfected their start and any change is, again, probably a waste of time.

So why chase new and different race starts at all?  My answer is: because no crew is the same as the next.

Getting back to acceleration, the basic philosophy of a race start is to get from dead stop at the starting line to race pace as quickly as possible.  I’ll ignore “as efficiently as possible” because when it comes to 500m or less, who cares who did it the cleanest if they lost to a team with a “messy” start?  If efficiency was poor in the faster team, it just means that team could have accelerated faster next time.  To me, a winning start is plenty efficient no matter how it looks.  Think of how noisy, messy, and almost out of control a drag race car start is compared to driving around your Prius.  The dragster was efficient at accelerating like a beast while the Prius was efficient at saving fuel and not waking the neighbors.  The dragster wins.  Be the dragster.

But how do you know if a start is giving efficient acceleration?  Well, you could test like I used to with a GPS and stopwatch or utilize buoys of known distance.  Find your team’s sustainable race pace and seek to get to that speed ASAP.  There’s the chance for playing around with ratios and technique.  The goal is to eliminate dead-spots in acceleration on the way to full race pace.  The other goal is NOT to completely overshoot race pace and exhaust the crew before you get past the 100m mark (unless 100m is the race).

On to ratios and technique, faster acceleration demands a greater amount of power.  Power is the rate at which work is done.  Each paddle stroke does some work.  Stroke too long and slowly and power is lost.  Rate up too quickly and shorten the stroke, power is also lost.  The sweet spot for every team lies in the middle somewhere.  Physically stronger, more explosive teams can afford to rate up faster because they can put out more power.  Weaker teams may benefit from an intentionally more gradual workup.

Once the start is over, the time to accelerate is done.  Some teams opt for a high stroke rate during the race because it seems “faster.” (as in people moving their bodies/paddles quickly must be making the boat move faster, right?)  Well, again it depends on how the team can physically maintain their chosen race velocity.  If the team can ONLY generate adequate power to sustain that chosen speed, then sure, thrash away.  Their hearts will probably be running a few extra beats/min higher than a team that is able to maintain the same boat speed but at a lower stroke rate.  If you have a paddling erg, you can see how your heart rate changes if you decrease the paddle resistance and hold a higher stroke rate during a time trial vs a slightly heavier pull but lower stroke rate over the same distance.

Case in point, you can see how DW drops the stroke rate but maintains their boat speed while other adjacent teams maintain high stroke rate without gaining ground:

Compare that to our video from the 2009 Sprint Race where SFL was doing dry starts with rather meek acceleration between strokes 0-2.  I definitely do not think the strongest SFL team of its day could stand up to the crews of today, mostly based on the average physical fitness of modern, A-div teams.

I’m still proud to say that I was able to coach a crew of highly dedicated and passionate paddlers of a wide variety of fitness levels and skill into becoming a consistent contender for A-div podiums over the course of several seasons.  Thanks for the memories, everybody!