Prognostic Times

Prognostic times (PTs,
or Gold Standards) are widely used in rowing communities for various purposes,
such as: 1) Defining training intensity; 2) Evaluation of performance in various
boat types; 3) Selection of rowers and crews; 4) Benchmarking and setting
targets for short and long-term rower’s development; 5) Motivation for rowers
and coaches to achieve the highest standards.
Usually, PTs
are developed at National Rowing Federations (NRFs). Our Google search reveals
only two open sources (Table 1) from Australia (1) and Canada (2), which means
that most of NFRs keep their PTs in secret. All published NRF’s
prognostic times are anonymous and methods of their development were not disclosed,
so it is likely that they are subjective, which creates the following problems:
it is not possible to discuss PTs to make them more accurate and
eliminate discrepancies between them, which may lead to errors in crews
selection. Usually, NRFs PTs are set close to or higher than
World Best Times (WBTs), which are unrealistic to achieve without very fast
weather conditions.
In an attempt to find an
objective method of PT calculation, two different methods could
be used:
1.
Statistical method using trends of speed of the winners of World
regattas. Advantages: Relatively simple and obvious, does not require biomechanical
measurements. Disadvantages: Low reliability due to the effect of random
weather conditions.
2.
Biomechanical modelling using rowing power and drag factors in various
boat types. Advantages: Ability to model rowing speed for various rower’s
power/weight ratios and various weather conditions. Disadvantages: Requires
additional complex measurements, uncertainty of the real power production in a
race (usually, only erg scores are available) and the effect of weather.
Here is a
description of both methods to make them available for others to produce their own
objective PTs (say, for juniors, U23 and other rower’s
categories), as well as our BioRow PTs-2024 for elite rowers. Analysis of speed
trends with method 1 consists of two steps: 1) Data filtering, 2) Selection of
the most adequate trend type.
Step 1. The
data must be filtered to exclude outliers, mainly on the slow side, and the
filtering range must be chosen adequately: e.g., in W2x (Fig.1), filtering data
within ±1.5SD range with exclusion of only one (the
slowest) data point in 2016 (1) improves the PT by 9s, from 6:49 down
to 6:40 and increases the significance from 8% up to 31%.
Step 2: An
adequate trend type should be selected, which is usually a linear, 2nd and 3rd
order polynomial trend. E.g., in W2x, using a linear or third order polynomial
trend would give PT2024 6:40 (Fig.1), but using the second order trend would
give 6:49. In M2x, using a linear trend would give PT2024 6:03, the second order
– 6:06, the third order – 5:57. The following rule can be used to make the selection
of trends more objective: if two trend types produce a similar PT,
they should be used for this boat type (as was in W2x above); if all three
trends produce different PTs (in M2x), the median PT should be selected.
Biomechanical
modelling (method 2) is based on an equation relating the prognostic speed V
with rowing power P and drag factor DF in a
specific boat and rower’s mass:
Rowing
power P could be derived from the known erg score of the rower(s).
However, it is not a fact that this exact amount of power is really produced in
the race on-water, especially in big sweep boats, which is a limitation of the
method. Drag factors DF in various boat types were derived from the
BioRow database of
biomechanical measurements (n>30k), usually in a tail wind. Two types of DF
were identified (RBN 2015/04): DFnet
, which excludes blade and boat velocity efficiencies, and DFgross, which is the ratio of
rowing power to the cube of the boat speed. DFgross was
used here for simplicity and derived as a linear function of the average
rower’s mass.

Hopefully, the development of prognostic times will become more open and objective in a future, assisted with attempts from FISA to bring more information to the rowing community about weather conditions during World regattas, and possibly about other indicators of rowing performance.
1. Australian Gold Standard times. http://194.81.104.27/~brian/Rowing/TrainingPlans/GMPT.pdf
©2020 Dr. Valery Kleshnev www.biorow.com