Friday Five – 4/28/17

The Friday Five is a set of five links that I have come across this week that pertain to ergonomics, occupational health, safety, human performance, or human factors.  For whatever reason, I found them interesting, but they are provided with minimal or no commentary and are not meant to be endorsement for a given product or research paper.

These links were generated during a PubMed search on the terms: applied ergonomics

Lee et al. investigated the position of two different wearable sensor systems on the posture of construction workers while performing assigned tasks in a laboratory.  As those who have worked with motion capture devices know, placement of these sensors is everything in terms of collected data.

He et al. look at using Google Glass to monitor eye blinking in drivers to determine signs of drowsiness.  Distracted driving is something that we’ve hit upon in other posts.  Technology such as this may be able to go along way in helping drivers to recognize when they are too fatigued to drive safely.

Schmidt et al. investigated a different way of dealing with fatigue during long drives through the use of a cooling device to help improve alertness.

Armstrong et al. reviewed the impact of two paramedic services transitioning to a powered stretcher to help reduce injuries related to patient transport.  This appears to be a cost-effective solution with a reduction in injuries during patient transport.

Hlavenka et al. investigated the effect of neck posture during lifting tasks on both lumbar spine posture and activation of trunk musculature.  They indicate that a retracted neck posture may help to lower the risk of pain and injury during lifting tasks.

 

Mythbusters, Doom, and the effect of fitness

The Science channel has been running a marathon of Mythbusters episodes to get ready for the Mythbusters: The Search which has kept my children (and me) entertained over the New Year’s weekend.  This morning, I found my son watching an episode where they decided to evaluate whether some videogames were “Plausible” or “Busted”.

One of the “myths” dealt with chainsaws and fruit in looking at the Fruit Ninja game and would probably make a great post about chainsaw safety for later.

But the one that caught my eye for the things that they didn’t really talk about was the Doom myth.  Plenty of websites discuss the fact that Jamie and Adam created a “pseudomyth” for this episode in looking into whether the space marine in Doom could actually carry all 9 items that they were able to play with while completing game levels.  Doom, as one of the original first person shooter games, took a lot of license with reality – but, it’s a game.  More recent games, such as FallOut, take into account what a player is carrying or their physical state in determining how fast they can move, how high they can jump, etc.

The goal that Jamie and Adam set out to determine was what was the time impact on carrying the full load of weapons and med kits on completing a simulated game level in real life.  They each completed the level as fast as they could, picking up and dropping weapons as they went as their control time.  Then Jamie and Adam each went through, using their own carry strategies, and picked up and carried each of the nine items as they acquired them.  The total weight by the end of the level was 80 pounds, made up of medkits, weapons, and ammunition packs.  Jamie and Adam are not physical fitness specimens, but are not out of shape either.  By their admission, they have what they would call an average level of fitness.  Their second runs (avg. 11:08) were each almost twice as long as their “clean” runs (avg. 5:45).

They then took one extra look at the scenario and brought in UFC fighter Brendan Schaub to make an attempt at the course.  Schaub’s control time (4:00) and his carry time (4:03) were nearly identical.

While this was just a one-off “experiment” for a tv show that was simulating the events of a video game, there are a couple of things that we can learn from this episode about the impact of fitness on performance.

  • The much fitter individual (Schaub) was significantly faster under both conditions than people that are of average fitness.  He was nearly 2 minutes faster.
  • When someone is truly fit loading up with a significant load does not place a significant effect on overall performance – even when it is placing a significantly greater demand on the body.  I wish that they had performed all of the runs with at least a HR monitor on the three of them – or even better, a Cosmed portable metabolic unit, to better quantify the overall difference in demand between the two scenarios.  A US military study looked at the difference between two type of uniforms/load bearing vests on a simulated march, but it does not look at the difference between unloaded and loaded performance.
  • When you are of average fitness, the addition of significant physical load can cause significant changes to your ability to perform a given task.

Again, this is a tv episode simulating a videogame but the actual weight load of 80 pounds has some real world comparisons:

  • The gear worn by firefighters (protective clothing, boots, gloves, helmet, SCBA unit) weighs approximately 80 pounds.
  • Combat soldiers routinely carry loads in excess of 60 to 90 pounds with greater loads based on length of patrol.
  • Bags of cement, used both at home and on job sites, commonly weigh 80 pounds and are carried for short distances.
  • We have measured school furniture (multiple times) that is moved by custodial staff at the beginning and ends of the school year that can require between 65 pounds and 100 pounds worth of weight to be carried by each individual moving the item.

Activity calculators, which provide the METs (metabolic equivalents) to describe the physical demand of a task put carrying a 1-15 pound load up a flight of stairs as 5 METs while carrying a 70 pound load in 10 METs and 74+ pounds brings the demand to greater than 12 METs. For comparison, walking on a job site comes in at an easy 2.5 METs while carrying a load of 75 pounds or more on level ground comes in at 8.5 METs.  This applies to the real world for EMTs, firefighters, and police – part of their normal activities include helping to bring equipment up stairs as well as downstairs.  Transport EMTs often bring patients back up the stairs in apartment buildings when returning them from a medical visit when their is no elevator available. Over ground fighting of fires has also been measured to be in the 12 MET or greater category.  This places daily job demands for these individuals in the 10 to 12 MET category.

Interestingly, for firefighters, they have begun to address the issue of cardiovascular fitness in determining what activities can’t be performed if the firefighter can’t perform up to an 8 MET level on a standardized treadmill test.  Remember from earlier, tasks that a firefighter performs are in the 12 MET demand category.  Section 8.2.2.1 of the NFPA 1582 guidelines places these restrictions when an individual can’t perform up to an 8 MET level on a standardized treadmill test:

  • While wearing personal protective gear and SCBA, performing fire-fighting tasks
  • Wearing an SCBA, which includes a demand valve-type positive pressure facepiece or HEPA filter masks, which requires the ability to tolerate increased respiratory workloads
  • Climbing six or more flights of stairs while wearing fire protective ensemble weighing at least 50 pounds or more and carrying equipment/tools weighing an additional 20 to 40 pounds
  • Wearing fire protective ensemble that is encapsulating and insulated, which will result in significant fluid loss that frequent progresses to clinical dehydration and can elevate core temperature to levels exceeding 102.2o F
  • While wearing personal protective ensembles and SCBA, searching, finding, and rescue-dragging or carrying victims ranging from newborns up to adults weighing over 200 pounds to safety despite hazardous conditions and low visibility
  • While wearing personal protective ensembles and SCBA, advancing water-filled hoselines up to 2.5 in diameter from fire apparatus to occupancy [approximately 150 ft], which can involve negotiating multiple flights of stairs, ladders, and other obstacles
  • While wearing personal protective ensembles and SCBA, climbing ladders, operating from heights, walking or crawling in the dark along narrow and uneven surfaces, and operating in proximity to electrical power lines and/or other hazards
  • Unpredictable emergency requirements for prolonged periods of extreme physical exertion without benefit of warm-up, scheduled rest periods, meals access to medication(s), or hydration
  • Functioning as an integral component of a team, where sudden incapacitation of a member can result in mission failure or in risk of injury to civilians or other team members

Hopefully, other professions will begin to take a stronger look at the physical demands and the fitness levels of those performing the tasks.  Physical fitness is a key component to task performance when we are talking about more than light loads.  When the actual physical demand of a task increases to the limits of an individual’s fitness level, the risk of injury increases dramatically.

Note: At the time that this was filmed and originally aired, Brendan Schaub was still competing in the UFC.  He retired later that year, so please don’t write to tell me that he is a retired UFC fighter.