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Home  >  Topics  >  Officer Safety

October 07, 2013
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Force Science Institute Destroying Myths & Discovering Cold Facts
with Force Science Institute

New sprint study: Are you prepared for this offender speed?

The goal was to measure and analyze at what speed, with what stride length, and in what time frame can the average subject run full-out and move in different directions from various starting positions

New time-and-motion research by the Force Science Institute has important implications for officers in defending themselves against close-quarters attacks, according to FSI’s executive director Dr. Bill Lewinski. A companion study — now nearing the reporting stage — will shortly reveal for the first time the extent to which duty gear and protective equipment on an officer’s body slow down his or her movements in critical situations. 

“Both these studies underscore the importance of making training exercises dynamic and realistic,” Lewinski told Force Science News.

“The wealth of data gathered can help trainers to expose officers to the true speeds at which assaults can occur and condition them to approach and respond to dangerous threats accordingly. Investigators and force reviewers can use these findings to better assess the behavior of both officers and suspects in situations where an officer is assaulted. And they arm administrators and PIOs with more scientific information to use in educating the media and the public about the realities of violent encounters,” Lewinski said

Sprint Performance
Besides Lewinski, the team conducting the first study included Jennifer Dysterheft and Dawn Seefeldt of FSI’s research staff and Dr. Robert Pettitt, associate professor in the Human Performance Dept. at Minnesota State University-Mankato. The project was coordinated by Patricia Thiem, FSI’s chief operating officer. 

Their goal was to measure and analyze “sprint performance” — at what speed, with what stride length, and in what time frame can the average subject run full-out and move in different directions from various starting positions. 

Among other things, Lewinski points out, these findings can help define an officer’s vulnerability to an offender with an edged weapon or blunt object at relatively close distances. 

“We’ve known for years from researcher Dennis Tueller and previous Force Science studies how fast knife-wielding suspects can attack from 21 feet or farther,” Lewinski explains. “But many edged weapon assaults occur in kitchens or living rooms or bedrooms, for example, where distances may be 10 feet or less. What challenges are officers facing in those circumstances?” 

The Tests
The researchers tested 13 male and six female civilian volunteers, most in their early- to mid-20s, reflecting an age group common among offenders. About half had some school athletic experience that included sprinting, such as football and baseball. However, they were not specifically trained as sprinters. 

Wearing athletic shoes, each was videotaped performing a series of sprints in a gymnasium, running from a dead start as fast as possible forward, back-peddling, and turning at a 90-degree angle and running to the right and to the left. 

For some trials, subjects were told to maintain eye contact with a fixed, lateral focal point while sprinting to see if that affected their performance. This simulated an officer trying to escape from the path of an oncoming vehicle to avoid impact. 

Afterward, the time-stamped video was subjected to a sophisticated and precise computer analysis to measure the length of each subject’s first six strides, the time it took to make each step, and the acceleration the sprinter gained as he/she moved. Comparisons were made in each category between subjects who concentrated on a focal point and those who did not. 

Stride-by-Stride Results
In a report of the study to be published in a future issue of the International Journal of Exercise Science, the researchers present a detailed grid of the averages they determined. This grid also can be accessed in metric- and imperial-unit format on the Force Science website

Lewinski recently walked us through a sampling and explained some of the implications. 

Stride length. Sprinting straight forward from a starting position, the average subject (let’s say a suspect charging toward an officer) covers more than three feet in his first stride. His third step stretches out to more than four feet, and by his sixth stride he’s closing distance at more than 5 feet per stride. 

Back-peddling from a starting position (as a startled officer might do in trying to escape an attack), the average first step is barely two feet and doesn’t reach three feet even after six strides. 

Step time. The average forward sprinter takes a first step in about a third of a second and follows with subsequent steps about every quarter-second. He can propel himself through 6 strides in slightly more than a second and a half, the researchers found. 

Stride velocity. By the time he hits his fifth stride, he’s sprinting at just over 13 mph. “A back-peddler — if he hasn’t already fallen by then — is nowhere close to that speed,” Lewinski says. “Civilians can move really quickly in launching an assault, and true to form, a reacting officer is at a marked disadvantage, especially in trying to escape backwards.” 

Focal-point effect. The researchers detected only negligible differences in real-world application between the subjects who “just put their head down and ran as fast as they could” and those who concentrated on a visual focal point, Lewinski notes. 

“For years there has been controversy over which way is faster, but the difference turns out really to be of no significance.” 

Backward step. Researchers found that subjects who first took a quick backward step with their dominant leg and pushed off from there when turning to sprint to the side were generally able to generate more power and force, thus increasing their acceleration for short distances. This could have implications, Lewinski says, for officers trying to get out of the way of an approaching threat, such as a speeding vehicle. 

90-degree turn. To assess the speed of dynamic movement on the part of an assailant while engaging an officer in a gunfight, Force Science has studied the 90-degree turn in three separate studies. In FSI’s first study in which subjects had a gun in their hand and simply turned 90 degrees, without pointing the gun, the time to complete the turn was just under one third of a second. 

In FSI’s second study they tested the time for an assailant to fire at an officer and then escape by turning 90 degrees and running. The average time to turn, once the assailant completed firing, was 37/100ths of a second or just over a third of a second. 

In this current study the average time for someone to turn into a 90-degree angle and take one full step without a gun in hand, is still approximately one third of a second. The time will vary slightly depending upon whether the person maintains a fixation point on the officer, or not, and whether they are turning to the left or right but the first stride covers approximately three feet and the person has reached a velocity of just under seven miles per hour. 

Implications
This study is the first phase of an extended sequence of time-and-motion research, Lewinski says. Long-term, its core value may be in establishing baseline measurements for speed, movement, and distance against which a range of variables can be tested. 

Yet even these basic data raise some important questions for trainers, street officers, and other law enforcement principals. For example: 

• “Our findings show that a suspect standing 9 feet from an officer can charge at him and be close enough to reach out and slash him with an edged weapon in just over half a second. Starting just 5 feet away, a determined offender can be stabbing an officer with his extended arm in a third of a second,” Lewinski says. “What does this do to the traditional thinking about a reactionary gap and about a preemptive use of force?” 
• “Given the documented slowness of back-peddling, are officers being trained to make — and practice — well-timed and well-coordinated J turns and L moves as escape tactics?” 
• “Understanding that suspects may flee and shoot back at the same time, are officers practicing shooting at targets that are moving away from them at some angle as fast as this study shows an average attacker can sprint, perhaps up to 13-15 mph?” 
• “Do they understand and practice what they need in terms of time and stride distance to move out of the way of an oncoming vehicle that a suspect is deliberately driving toward them? Given our clearer understanding of the relationship between time, distance to be covered and proximity of an officer to a vehicle it is now more feasible to train officers to accurately evaluate the degree of risk posed by an oncoming vehicle and to help them determine whether getting out of the way is a safe, reasonable option or whether shooting to stop or divert the driver is the only necessary course of action given the circumstances. 
• “Are investigators and force reviewers prepared to consider the speed with which offenders can attack from relatively short distances when analyzing an officer’s defensive actions?” 
• “Likewise, can departmental spokespersons use this information appropriately in public to explain uses of force that might otherwise seem questionable?” 

The Next Phase
Data from Phase two of this research has already been gathered and is currently being analyzed for publication. The central thrust of that project is to determine the extent to which an officer’s movement in threat situations is slowed by the duty gear and protective equipment that weigh him/her down. 

That study, headed by Lewinski, was conducted in an academy setting in Minnesota and involved testing more than 20 law enforcement students in sprint trials with and without 20 pounds of equipment. 

Final results of their performances are expected shortly and will be reported by Force Science News. We’ll also announce the report about the current study in the International Journal of Exercise Science when it is in print.


About the author

The Force Science Institute was launched in 2004 by Executive Director Bill Lewinski, PhD. - a specialist in police psychology -- to conduct unique lethal-force experiments. The non-profit Force Science Institute, based at Minnesota State University-Mankato, uses sophisticated time-and-motion measurements to document-for the first time-critical hidden truths about the physical and mental dynamics of life-threatening events, particularly officer-involved shootings. Its startling findings profoundly impact on officer training and safety and on the public's naive perceptions.

For more information, visit www.forcescience.org or e-mail info@forcescience.org. If you would benefit from receiving updates on the FSRC's findings as well as a variety of other use-of-force related articles, please visit www.forcesciencenews.com and click on the "Please sign up for our newsletter" link at the front of the site. Subscriptions are free.





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