The Paradox of Injury
It’s has often been stated that health ends where sport begins! No one gets inherently healthy playing high level sport. Yes, athletes are in great physical condition, but health is a much broader construct than looking good in a t-shirt. Bangs, bruises, avulsions, lacerations and concussions happen daily in high contact sports such as hockey. The game moves at high speeds and the forces of impact endured by collisions are that of a minor car crash. Orthopedic injuries are a common in today’s game. The paradox is quite simple, with all of the technology, money, resources and people power, injury reduction has been debatable at best. In fact, depending on how you interpret the numbers (averages, median) rates have risen. I was reminded of this a year or so ago, from a Tweet by NBA commentator Stan Van Gundy, he stated:
“90’s NBA teams had just a trainer and a SC, they practiced more often and harder and played more back to backs. Teams now have huge medical & “performance” staffs and value rest over practice. Yet injuries and games missed are way up. Something isn’t working.”
I pondered the same question in the sport of ice hockey. Are injuries up, down, or relatively stable?
NHL Injury History Chart (Click MGL boxplot)
Side Notes:
*Assumption: Almost half the league had a dedicated Sports Scientist by the 2015-2016 season
*The 2012-2013 season was cut short due to lockout
*The 2019-2020 season was cut short due to COVID
*The 2020-2021 season was cut short due to COVID
In 2000-2001, the league had 30 teams. In 2017-2018, **Vegas was added to the league and in 2021-2022, ***Seattle was added, making the league a 32 team
The Numbers
Numbers are always up for interpretation. What is the universal definition of what constitutes an injury? How are injuries calculated for each team? Do players play injured during certain portions of the year? Regardless, injuries per 1000 game hours in often used in research as the gold standard. [1] Injury per 1000 player-game hours is based on a 60-min active game and is calculated as the number of injuries/number of players on the ice at the same time (6)/number of games x 1000. It appears that that there has not been a considerable decrease in this number over the last 24 years. In fact, it’s relatively stable. The average injury per 1000-player game hours from 2000-2024 is 19.8 games. Look at the red trend line of injury per 1000 games and compare the fluctuation to the mean (the straight blue line). This is the regression towards the mean.
Injury per 1000 player-game hours is based on a 60-min active game and is calculated as the number of injuries/number of players on the ice at the same time (6)/number of games x 1000.
From 2000-2012: 7 seasons this number was at or under the average
From 2012-2024: 7 seasons this number was at or under the average
Average Man games lost (MGL)/team appear to have risen 2.5% from the period 2000-2012 - 2012-2024
From 2000-2012: The average MGL/team was 242.26, the median average MGL/team was 239.7
From 2012-2024: The average MGL/team was 247.9, the median average MGL/team was 233.4 (*2021-2022 saw a record MGL and Avg MGL/season)
The Potential Causes
Training: Players are bigger, faster and stronger. Training has evolved. In fact, increasing strength, speed and mass actually may increase (not decrease) the chance of orthopedic injury. Yes, that’s right! Increase injury. It all has to do with basic physics. Kinetic energy and force at impact play an important role in our understanding.
The ice surface has a minimal friction so players can reach higher speeds. Looking at the kinetic energy equation (k = 1/2 m x v2), both mass (m) & velocity (v) play an important role.
An object with twice the mass and equal speed will have twice the kinetic energy, while an object with equal mass and twice the speed will have quadruple the kinetic energy. At these speeds injuries are likely to occur.
The force of impact = change of Kinetic energy/deformation distance. Higher speeds, higher mass equate to larger forces. In fact, the goal of equipment companies in to spread that impact over larger surface areas affecting the denominator in this equation. Bottom line, increased performance equates to larger forces at play, and larger forces to accept during high-speed collisions.
Game Schedule: 82 car crashes per year. That’s a lot of hockey. Though game schedule is not in the control of the performance professional, managing this stress throughout the year is critical. Coupled with schedule is travel, sleep, nutrition and lifestyle. Injury is complex.
Implications for Sports Science - Hindsight vs Foresight
According to an article published in in The Athletic written in 2017, 15 teams in the NHL have someone with a job title related to sports science. That was roughly half the league. It can be assumed that this number continues to grow. Depending on how you view the numbers:
Average MGL/team have risen since this time frame
Median Avg MGL/team has declined slightly
Can sports science solve the problem?
Hindsight is the easy part. Foresight, not so much. In hindsight uncertainty doesn’t exist; we know what happened! Explanations are plentiful. As Phillip Tetlock states “we have an uncontrollable need to believe in a controllable world.” Today, data, technology, metrics, and testing permeate the sport scientist. The fact is no technology, no measure, no metric or statistical ratio can predict injury. At best, we can use these tools to measure initial baselines, and once injuries occur, we can provide both objective and subjective feedback regarding status. Unfortunately, in the world of injury, we are “hindsight” beings!
“Just as the financial advisor can produce a respectable explanation for yesterday’s stock results, the complex strategy can weigh its many reasons so that the resulting equation fits well with what we already know. Yet, in an uncertain world, a complex strategy can fail exactly because it explains too much in hindsight. Only part of the information is valuable for the future, and the art of intuition is to focus on that part and ignore the rest.” -Gerd Gigerenzer
We mustn’t get overly enamored with fancy measures and complicated post hoc explanations used to predict injury. People, principles, process and provisions are key for any culture. However, today one must be conscious of focusing too much on the provisions without questioning the reliability, importance, feasibility and content knowledge within the environment in which we operate. Bottom line, based on the aggregate injuries have not decreased. Tech is not the answer! Perhaps a better question emerges from this dialogue? How should we be evaluated?
Man-Games Lost (I think this is overly simplistic and perhaps unfair)
Content knowledge
Winning percentage
Solving problems (using the scientific method) for coaches
Like-ability
Communication-Reliably
Ability to work with others
The answer is multi-factorial. Just like we mustn’t marry methods in the S&C realm, we shouldn’t marry methods in the tech/injury realm either. Being the external load guy, the resisted sprint guy, the sleep guy, the force plate guy, the asymmetry guy is the equivalent to hyper focusing on the method without understanding the complexity of the landscape.
In contact sports such as hockey injuries don’t seem to be going anywhere. Great testing/monitoring can serve to collect baseline numbers, reinforce recovery, and provide objective feedback, but we mustn’t confuse and accurate measure with a good measure, and at the current moment, we don’t have a good measure to predict injury.
“Doubt is not a pleasant condition, but certainty is absurd.” -Voltaire.
1. Donskov, A.S., D. Humphreys, and J.P. Dickey, What Is Injury in Ice Hockey: An Integrative Literature Review on Injury Rates, Injury Definition, and Athlete Exposure in Men’s Elite Ice Hockey. Sports, 2019. 7(11): p. 227.
