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      <p begin="00:00:01.37" dur="00:00:03.19">Welcome to the next in our series of Sportsturf Scoop videos.</p>
      <p begin="00:00:04.86" dur="00:00:01.56">Today we will be focusing on Gmax –</p>
      <p begin="00:00:06.76" dur="00:00:02.15">one of the most commonly tested characteristics</p>
      <p begin="00:00:08.92" dur="00:00:02.93">of synthetic turf fields and natural grass fields.</p>
      <p begin="00:00:13.98" dur="00:00:02.23">So before we get into how Gmax testing is done</p>
      <p begin="00:00:16.40" dur="00:00:01.21">and what those numbers mean,</p>
      <p begin="00:00:18.26" dur="00:00:01.93">lets take a look at what Gmax really is.</p>
      <p begin="00:00:21.03" dur="00:00:01.91">Really, it is a measure of how much force</p>
      <p begin="00:00:22.94" dur="00:00:02.70">the surface absorbs and in return,</p>
      <p begin="00:00:25.65" dur="00:00:01.49">how much is returned to the athlete.</p>
      <p begin="00:00:28.07" dur="00:00:00.97">What we think about this</p>
      <p begin="00:00:29.06" dur="00:00:02.73">in terms of is in the context of head injuries.</p>
      <p begin="00:00:31.79" dur="00:00:02.81">Normally when we think about head injuries during play,</p>
      <p begin="00:00:34.61" dur="00:00:02.05">we think about a helmet to helmet hit and</p>
      <p begin="00:00:36.67" dur="00:00:02.51">certainly that is where we see the majority of head injuries.</p>
      <p begin="00:00:39.80" dur="00:00:00.86">But in reality,</p>
      <p begin="00:00:40.81" dur="00:00:01.59">some research has shown that up to</p>
      <p begin="00:00:42.40" dur="00:00:02.38">10% of concussions are caused by</p>
      <p begin="00:00:44.78" dur="00:00:01.15">impacts with the surface.</p>
      <p begin="00:00:46.53" dur="00:00:01.45">So the level of hardness or</p>
      <p begin="00:00:47.98" dur="00:00:01.97">how much force the surface absorbs</p>
      <p begin="00:00:50.34" dur="00:00:02.62">does influence head injuries during sporting events.</p>
      <p begin="00:00:54.82" dur="00:00:03.08">So diving a little deeper now into what Gmax really is –</p>
      <p begin="00:00:58.09" dur="00:00:02.19">lets first talk about the unit that it is measured in,</p>
      <p begin="00:01:00.30" dur="00:00:02.75">and obviously Gmax is measured in g’s.</p>
      <p begin="00:01:03.14" dur="00:00:03.31">So, 1 g is equal to the acceleration due to gravity.</p>
      <p begin="00:01:06.45" dur="00:00:01.50">We can think about g’s –</p>
      <p begin="00:01:07.96" dur="00:00:02.57">think about a fighter pilot as he is performing</p>
      <p begin="00:01:10.54" dur="00:00:01.74">his maneuvers in the air he is “pulling g’s”</p>
      <p begin="00:01:12.28" dur="00:00:01.67">as he is doing these extreme maneuvers –</p>
      <p begin="00:01:14.35" dur="00:00:02.26">same idea with Gmax – it is the same unit.</p>
      <p begin="00:01:17.51" dur="00:00:01.91">What we are measuring with Gmax obviously</p>
      <p begin="00:01:19.63" dur="00:00:02.06">is measuring the magnitude of impact</p>
      <p begin="00:01:21.70" dur="00:00:01.70">or the peak deceleration.</p>
      <p begin="00:01:23.41" dur="00:00:02.11">So we drop a missile or a weight onto the ground –</p>
      <p begin="00:01:26.25" dur="00:00:02.31">how fast does that missile or weight stop?</p>
      <p begin="00:01:29.54" dur="00:00:05.09">A definition of Gmax is the maximum negative acceleration on impact.</p>
      <p begin="00:01:36.63" dur="00:00:02.32">So now we can start applying this to athletic fields.</p>
      <p begin="00:01:39.55" dur="00:00:01.54">Think about athletic fields in terms</p>
      <p begin="00:01:41.09" dur="00:00:02.01">of how many g’s can the surface absorb?</p>
      <p begin="00:01:43.70" dur="00:00:01.06">And on the flip side,</p>
      <p begin="00:01:44.77" dur="00:00:01.56">how much is returned to the athlete?</p>
      <p begin="00:01:46.98" dur="00:00:02.06">So a high Gmax level means</p>
      <p begin="00:01:49.04" dur="00:00:01.74">that there is less absorption of force</p>
      <p begin="00:01:50.79" dur="00:00:02.11">by the surface and more is returned to the athlete.</p>
      <p begin="00:01:52.90" dur="00:00:01.22">So you can imagine</p>
      <p begin="00:01:54.13" dur="00:00:01.83">the Gmax of a parking lot is very high,</p>
      <p begin="00:01:56.59" dur="00:00:02.75">and the Gmax of a mattress is very low.</p>
      <p begin="00:02:01.79" dur="00:00:02.49">Now that we have an understanding of what Gmax is,</p>
      <p begin="00:02:04.64" dur="00:00:02.29">how do we go about testing an athletic field?</p>
      <p begin="00:02:07.28" dur="00:00:03.64">For that, we go to the American Society for Testing and Materials or ASTM.</p>
      <p begin="00:02:11.62" dur="00:00:02.79">So for synthetic turf there are 2 standards that we deal with –</p>
      <p begin="00:02:14.42" dur="00:00:03.50">and that is the F355 standard and F1936.</p>
      <p begin="00:02:18.64" dur="00:00:03.08">Basically F355 outlines the test device –</p>
      <p begin="00:02:21.86" dur="00:00:03.50">what device do you use to test Gmax on a synthetic turf field.</p>
      <p begin="00:02:25.59" dur="00:00:03.02">F 1936 talks about the procedure we go through and</p>
      <p begin="00:02:28.62" dur="00:00:01.96">we will talk about these here in the next few slides.</p>
      <p begin="00:02:31.10" dur="00:00:00.72">For natural grass,</p>
      <p begin="00:02:31.90" dur="00:00:04.53">the ASTM specification that we need to look at is F1702.</p>
      <p begin="00:02:37.97" dur="00:00:03.00">If we take a closer look at ASTM F355 –</p>
      <p begin="00:02:41.15" dur="00:00:01.46">again this is the test method –</p>
      <p begin="00:02:42.94" dur="00:00:03.82">we see the F355 device which comes out of that method and</p>
      <p begin="00:02:46.80" dur="00:00:01.35">you can see that in the picture here.</p>
      <p begin="00:02:48.75" dur="00:00:03.05">Basically we have a plastic tube with holes in the sides</p>
      <p begin="00:02:51.82" dur="00:00:01.09">to allow ventilation and</p>
      <p begin="00:02:52.92" dur="00:00:02.48">allow the weight that is in there to freely fall.</p>
      <p begin="00:02:55.96" dur="00:00:02.03">So, basically we drop a weighted missile</p>
      <p begin="00:02:58.00" dur="00:00:03.12">that is housed inside that tube from a standard height and</p>
      <p begin="00:03:01.12" dur="00:00:02.12">inside that missile there is an accelerometer</p>
      <p begin="00:03:03.32" dur="00:00:01.86">that measures the impact</p>
      <p begin="00:03:05.18" dur="00:00:01.12">when that missile hits the surface.</p>
      <p begin="00:03:06.32" dur="00:00:00.90">So an accelerometer –</p>
      <p begin="00:03:07.22" dur="00:00:02.96">just like in a Nintendo Wii controller</p>
      <p begin="00:03:10.28" dur="00:00:01.43">allows you to see how much movement</p>
      <p begin="00:03:11.71" dur="00:00:00.95">you are getting and things like that –</p>
      <p begin="00:03:13.34" dur="00:00:00.62">same idea –</p>
      <p begin="00:03:14.01" dur="00:00:02.42">an accelerometer is placed inside that missile</p>
      <p begin="00:03:16.47" dur="00:00:02.10">inside that tube and as we drop that</p>
      <p begin="00:03:18.62" dur="00:00:04.59">we can get all sorts of data as that missile impacts the surface.</p>
      <p begin="00:03:24.52" dur="00:00:03.07">Really what this F355 device is made to do</p>
      <p begin="00:03:28.06" dur="00:00:02.28">is mimic a head falling onto the surface.</p>
      <p begin="00:03:30.95" dur="00:00:01.83">So if we look at how this was developed and</p>
      <p begin="00:03:32.79" dur="00:00:01.53">some researchers from here at Penn State</p>
      <p begin="00:03:34.32" dur="00:00:02.04">were involved with developing this device –</p>
      <p begin="00:03:37.04" dur="00:00:02.03">we have a missile which represents the human head.</p>
      <p begin="00:03:39.59" dur="00:00:01.86">So that missile must weigh 20 pounds and</p>
      <p begin="00:03:41.46" dur="00:00:02.75">that is to represent the human head and the neck.</p>
      <p begin="00:03:44.76" dur="00:00:02.29">It is also a flat-faced missile and</p>
      <p begin="00:03:47.06" dur="00:00:01.26">that goes back to some earlier testing</p>
      <p begin="00:03:48.32" dur="00:00:01.93">that was done on first generation AstroTurf</p>
      <p begin="00:03:50.25" dur="00:00:02.20">where they tried to use a hemispherical or</p>
      <p begin="00:03:52.46" dur="00:00:02.61">head-shaped missile that would tend to bottom out and</p>
      <p begin="00:03:55.07" dur="00:00:01.20">not give true readings,</p>
      <p begin="00:03:56.32" dur="00:00:01.13">so because of that,</p>
      <p begin="00:03:57.45" dur="00:00:02.91">we use a flat-faced missile like the picture you see here.</p>
      <p begin="00:04:00.84" dur="00:00:02.32">We drop that from a standard height of 2 feet.</p>
      <p begin="00:04:03.81" dur="00:00:01.26">All of this is based on research</p>
      <p begin="00:04:05.08" dur="00:00:02.21">that was done back in the 1960’s</p>
      <p begin="00:04:07.29" dur="00:00:01.50">on a lot of crash test dummies –</p>
      <p begin="00:04:09.06" dur="00:00:03.22">Ford and GM performing tests on heads impact windshields and</p>
      <p begin="00:04:12.28" dur="00:00:02.34">looking at the effects of injuring heads</p>
      <p begin="00:04:14.66" dur="00:00:01.63">in that type of situation.</p>
      <p begin="00:04:16.88" dur="00:00:02.01">Also the impact energy during a football game</p>
      <p begin="00:04:18.90" dur="00:00:03.96">was measured by adding an accelerometer to a helmet and</p>
      <p begin="00:04:22.86" dur="00:00:03.82">recording the different forces that occurred during a football game.</p>
      <p begin="00:04:28.74" dur="00:00:02.68">So lets say you have a testing agency out to test your field –</p>
      <p begin="00:04:31.95" dur="00:00:01.31">they are not just going to go out there and</p>
      <p begin="00:04:33.26" dur="00:00:03.00">drop the F355 on any spot out there on the field –</p>
      <p begin="00:04:36.27" dur="00:00:01.13">there is actually a way to do it and</p>
      <p begin="00:04:37.53" dur="00:00:02.96">that is outlined in ASTM F1936.</p>
      <p begin="00:04:41.21" dur="00:00:01.77">What we do when we go out to test a field</p>
      <p begin="00:04:42.99" dur="00:00:03.74">is we drop that F355 missile on 10 total points</p>
      <p begin="00:04:46.74" dur="00:00:02.12">on the field and on each of those points –</p>
      <p begin="00:04:48.87" dur="00:00:01.76">we drop it 3 consecutive times.</p>
      <p begin="00:04:51.32" dur="00:00:01.65">We take the average of the second and</p>
      <p begin="00:04:52.98" dur="00:00:01.18">third drop at each test point.</p>
      <p begin="00:04:54.99" dur="00:00:01.07">Now as far as test points go,</p>
      <p begin="00:04:56.10" dur="00:00:02.40">we can see that on this little picture of a field here.</p>
      <p begin="00:04:59.37" dur="00:00:02.78">There are 8 test points on a field that must be tested –</p>
      <p begin="00:05:02.31" dur="00:00:01.08">those are indicated</p>
      <p begin="00:05:03.39" dur="00:00:02.02">with the red circles with the yellow outline –</p>
      <p begin="00:05:05.42" dur="00:00:01.78">so you can see that on this football field here.</p>
      <p begin="00:05:07.77" dur="00:00:01.76">Now the final 2 spots can be selected</p>
      <p begin="00:05:09.53" dur="00:00:03.30">by either the field owner or the field tester.</p>
      <p begin="00:05:13.15" dur="00:00:02.06">In this case we are looking for spots</p>
      <p begin="00:05:15.22" dur="00:00:02.39">that may be extra-hard in a sense or</p>
      <p begin="00:05:17.61" dur="00:00:01.45">may have a high Gmax so areas</p>
      <p begin="00:05:19.07" dur="00:00:01.48">like bench areas or tunnel areas</p>
      <p begin="00:05:20.55" dur="00:00:01.86">may be tested to try to get</p>
      <p begin="00:05:22.47" dur="00:00:01.66">maybe a worse-case scenario.</p>
      <p begin="00:05:24.76" dur="00:00:03.02">So that is really how a field is tested for Gmax –</p>
      <p begin="00:05:27.97" dur="00:00:02.23">again there are 10 total points that must be tested.</p>
      <p begin="00:05:31.44" dur="00:00:01.39">So you have your field tested and</p>
      <p begin="00:05:32.83" dur="00:00:01.05">you get a nice report</p>
      <p begin="00:05:33.89" dur="00:00:00.97">back from the testing agency</p>
      <p begin="00:05:34.86" dur="00:00:01.01">that did the testing –</p>
      <p begin="00:05:36.17" dur="00:00:01.56">what do those numbers really mean?</p>
      <p begin="00:05:38.36" dur="00:00:02.38">Well, the main number you need to pay attention to is 200.</p>
      <p begin="00:05:41.43" dur="00:00:01.69">Anything above 200 g’s –</p>
      <p begin="00:05:43.50" dur="00:00:02.38">that is the point at which life threatening head injuries</p>
      <p begin="00:05:45.88" dur="00:00:01.26">may be expected to occur –</p>
      <p begin="00:05:47.15" dur="00:00:03.22">or there is a risk of life-threatening head injuries.</p>
      <p begin="00:05:50.37" dur="00:00:01.25">Now it is important to note</p>
      <p begin="00:05:51.63" dur="00:00:01.29">that this is life-threatening head injuries.</p>
      <p begin="00:05:53.54" dur="00:00:02.22">This does not necessarily apply to concussions.</p>
      <p begin="00:05:56.42" dur="00:00:01.99">There are a number of factors that affect concussions and</p>
      <p begin="00:05:58.41" dur="00:00:01.89">just putting one level of Gmax</p>
      <p begin="00:06:00.31" dur="00:00:01.33">on that is very difficult and</p>
      <p begin="00:06:01.64" dur="00:00:01.93">we do not have the science behind that right now</p>
      <p begin="00:06:04.18" dur="00:00:01.94">to really relate Gmax to concussions</p>
      <p begin="00:06:06.13" dur="00:00:02.42">so really is just a link between Gmax and</p>
      <p begin="00:06:08.56" dur="00:00:02.04">life-threatening head injuries.</p>
      <p begin="00:06:11.51" dur="00:00:02.90">Now that 200 level is accepted by both ASTM and</p>
      <p begin="00:06:14.41" dur="00:00:01.97">the U.S. Consumer Products Safety Commission.</p>
      <p begin="00:06:16.39" dur="00:00:01.22">So again, that is really the number</p>
      <p begin="00:06:17.61" dur="00:00:01.05">you need to pay attention to –</p>
      <p begin="00:06:18.76" dur="00:00:03.56">are any of those test points on your field above 200 g’s.</p>
      <p begin="00:06:24.12" dur="00:00:02.39">So we have just talked about maximum levels of Gmax,</p>
      <p begin="00:06:27.33" dur="00:00:01.40">is there a minimum level of Gmax? –</p>
      <p begin="00:06:28.74" dur="00:00:01.70">and the answer to that question is no.</p>
      <p begin="00:06:31.04" dur="00:00:03.50">There currently is no minimum standard for Gmax.</p>
      <p begin="00:06:35.17" dur="00:00:02.21">Now certainly we know a field can get too soft.</p>
      <p begin="00:06:38.01" dur="00:00:01.78">Think about running on dry beach sand –</p>
      <p begin="00:06:40.34" dur="00:00:03.08">you obviously cannot run as fast on that as say a parking lot.</p>
      <p begin="00:06:44.19" dur="00:00:03.80">Again, too soft of a surface decreases performance –</p>
      <p begin="00:06:48.03" dur="00:00:02.00">there are research studies out there that show that.</p>
      <p begin="00:06:50.51" dur="00:00:02.32">It also makes your muscles fatigue more quickly.</p>
      <p begin="00:06:53.36" dur="00:00:02.11">So as your muscles fatigue more quickly,</p>
      <p begin="00:06:55.48" dur="00:00:02.09">you are also at increased risk for injury.</p>
      <p begin="00:06:58.58" dur="00:00:03.22">No actual standard stating a minimum Gmax,</p>
      <p begin="00:07:02.33" dur="00:00:02.89">but again we need to think about a field can get too soft.</p>
      <p begin="00:07:07.56" dur="00:00:02.62">Now what are some other head injury tests you may come across?</p>
      <p begin="00:07:10.64" dur="00:00:01.86">Certainly we have talked about Gmax and</p>
      <p begin="00:07:12.51" dur="00:00:01.09">again that is the peak of the curve.</p>
      <p begin="00:07:14.13" dur="00:00:01.96">So in box A you can see what we are talking about.</p>
      <p begin="00:07:16.29" dur="00:00:03.68">The peak of that curve is about 90 – so our Gmax would be 90.</p>
      <p begin="00:07:20.75" dur="00:00:02.73">Now compare that to the severity index or the SI.</p>
      <p begin="00:07:24.16" dur="00:00:03.91">You can see in box b there the shaded area under the curve –</p>
      <p begin="00:07:28.24" dur="00:00:01.28">that’s really what we are talking about.</p>
      <p begin="00:07:29.53" dur="00:00:01.85">We are getting the total area under that curve –</p>
      <p begin="00:07:31.38" dur="00:00:02.91">so not only are we taking into account how high that peak is,</p>
      <p begin="00:07:34.30" dur="00:00:03.70">but also how long the duration of impact was.</p>
      <p begin="00:07:39.06" dur="00:00:01.46">Finally compare that to box c</p>
      <p begin="00:07:40.53" dur="00:00:02.58">which is our Head Injury Criterion or HIC score –</p>
      <p begin="00:07:43.11" dur="00:00:02.85">something that is used quite a bit in the automobile industry.</p>
      <p begin="00:07:46.54" dur="00:00:01.49">Very similar to the SI,</p>
      <p begin="00:07:48.38" dur="00:00:01.86">however we are removing some error</p>
      <p begin="00:07:50.25" dur="00:00:02.34">from the beginning and end of the curve.</p>
      <p begin="00:07:52.95" dur="00:00:01.37">So basically those two little tails</p>
      <p begin="00:07:54.33" dur="00:00:02.78">on the end of the curve are considered to be error and</p>
      <p begin="00:07:57.11" dur="00:00:03.38">not important in determining the head injury threshold.</p>
      <p begin="00:08:01.05" dur="00:00:02.30">So very similar to the SI, just a little bit different –</p>
      <p begin="00:08:03.41" dur="00:00:01.00">removing some error.</p>
      <p begin="00:08:07.15" dur="00:00:02.15">So just a little bit of a background on HIC score,</p>
      <p begin="00:08:09.79" dur="00:00:03.37">basically a HIC score of 1000 is considered the safe limit.</p>
      <p begin="00:08:13.28" dur="00:00:02.85">So we talked about 200 being the Gmax limit –</p>
      <p begin="00:08:16.43" dur="00:00:02.19">above that you get into the potential risk</p>
      <p begin="00:08:18.63" dur="00:00:02.40">for severe or life-threatening head injuries.</p>
      <p begin="00:08:21.20" dur="00:00:01.05">With the HIC score,</p>
      <p begin="00:08:22.25" dur="00:00:01.16">what they generally consider</p>
      <p begin="00:08:23.41" dur="00:00:02.12">to be that same safe limit is 1000.</p>
      <p begin="00:08:25.55" dur="00:00:03.73">Above that, the risk of a fatal head injury is non-zero.</p>
      <p begin="00:08:29.71" dur="00:00:02.41">Again we see this used more in the automobile industry and</p>
      <p begin="00:08:32.12" dur="00:00:01.62">also sports equipment if you look</p>
      <p begin="00:08:33.75" dur="00:00:02.21">on the back of a football or a hockey helmet,</p>
      <p begin="00:08:35.96" dur="00:00:02.78">you will see it is tested for HIC.</p>
      <p begin="00:08:40.78" dur="00:00:01.08">We have just spent some time</p>
      <p begin="00:08:41.87" dur="00:00:02.68">talking about measuring Gmax on synthetic turf fields –</p>
      <p begin="00:08:45.55" dur="00:00:01.89">there are other ways to measure Gmax.</p>
      <p begin="00:08:47.45" dur="00:00:03.10">In this picture here we see the Clegg Impact Tester.</p>
      <p begin="00:08:50.77" dur="00:00:01.26">This is the standard way</p>
      <p begin="00:08:52.04" dur="00:00:02.87">to measure Gmax of natural turfgrass athletic fields.</p>
      <p begin="00:08:55.68" dur="00:00:01.82">Same idea as the F355 –</p>
      <p begin="00:08:57.50" dur="00:00:01.31">we are dropping a weighted missile</p>
      <p begin="00:08:58.82" dur="00:00:01.96">from a standard height and</p>
      <p begin="00:09:00.78" dur="00:00:01.52">measuring peak deceleration.</p>
      <p begin="00:09:02.81" dur="00:00:01.61">In this case we have a lighter missile –</p>
      <p begin="00:09:04.68" dur="00:00:00.96">5 pound missile –</p>
      <p begin="00:09:05.90" dur="00:00:01.66">dropped from a height of 18 inches.</p>
      <p begin="00:09:08.22" dur="00:00:02.92">Interestingly, the impact energy overall</p>
      <p begin="00:09:11.14" dur="00:00:01.05">is very similar between</p>
      <p begin="00:09:12.20" dur="00:00:03.05">the Clegg Impact Tester and the F355.</p>
      <p begin="00:09:15.73" dur="00:00:01.73">Now those numerical values that we get</p>
      <p begin="00:09:17.47" dur="00:00:01.43">initially are not going to be the same.</p>
      <p begin="00:09:19.74" dur="00:00:01.77">The Gmax values are lower for the Clegg</p>
      <p begin="00:09:21.51" dur="00:00:01.50">than for the F355.</p>
      <p begin="00:09:23.01" dur="00:00:02.85">So, a 200 level with the F355</p>
      <p begin="00:09:25.87" dur="00:00:04.16">is roughly equivalent to 135 Gmax with the Clegg.</p>
      <p begin="00:09:30.06" dur="00:00:02.45">There is a mathematical relationship between the two</p>
      <p begin="00:09:32.52" dur="00:00:02.23">and we will talk about that in the next slide.</p>
      <p begin="00:09:35.55" dur="00:00:03.00">Incidentally, the cost of the Clegg Impact Tester</p>
      <p begin="00:09:38.56" dur="00:00:01.67">is much less than the F355.</p>
      <p begin="00:09:40.88" dur="00:00:00.83">As a field manager,</p>
      <p begin="00:09:42.00" dur="00:00:02.55">generally you won’t own an F355</p>
      <p begin="00:09:44.55" dur="00:00:01.89">but you could own a Clegg –</p>
      <p begin="00:09:46.75" dur="00:00:02.59">again this is just a few thousand dollar investment</p>
      <p begin="00:09:49.35" dur="00:00:02.31">you can make and monitor your field</p>
      <p begin="00:09:51.67" dur="00:00:01.14">on a more regular basis –</p>
      <p begin="00:09:52.81" dur="00:00:01.17">even a synthetic turf field –</p>
      <p begin="00:09:53.99" dur="00:00:03.07">you can test with the Clegg Impact Tester on a regular basis –</p>
      <p begin="00:09:57.24" dur="00:00:03.81">get an idea of what it would be with a F355 and</p>
      <p begin="00:10:01.05" dur="00:00:03.68">then use that in addition to regular F355 testing.</p>
      <p begin="00:10:04.74" dur="00:00:01.86">So something that a field manager can have on hand</p>
      <p begin="00:10:06.61" dur="00:00:03.45">to routinely monitor the Gmax of a field.</p>
      <p begin="00:10:11.98" dur="00:00:01.88">Now as part of our research here at Penn State</p>
      <p begin="00:10:13.86" dur="00:00:02.36">we have developed a mathematical relationship</p>
      <p begin="00:10:16.23" dur="00:00:03.29">between values obtained with the Clegg Impact Tester and</p>
      <p begin="00:10:19.52" dur="00:00:02.75">the F355 and data from all of our studies</p>
      <p begin="00:10:22.28" dur="00:00:01.24">can be found on our Web site.</p>
      <p begin="00:10:24.30" dur="00:00:02.06">So as you can see we have an equation here –</p>
      <p begin="00:10:26.40" dur="00:00:03.78">so we can really go back between the Clegg and the F355.</p>
      <p begin="00:10:30.33" dur="00:00:02.22">So if you are testing with the Clegg Impact Tester</p>
      <p begin="00:10:32.55" dur="00:00:00.93">you get a certain value,</p>
      <p begin="00:10:33.48" dur="00:00:02.86">you can plug that into this equation and</p>
      <p begin="00:10:36.34" dur="00:00:02.94">predict what you would get with a F355.</p>
      <p begin="00:10:40.07" dur="00:00:02.45">Now statistically this is a strong relationship –</p>
      <p begin="00:10:42.52" dur="00:00:02.98">in essence here our R squared value is 0.81</p>
      <p begin="00:10:45.51" dur="00:00:01.93">which indicates a strong relationship or</p>
      <p begin="00:10:47.44" dur="00:00:03.10">a strong predictive ability with this equation.</p>
      <p begin="00:10:51.41" dur="00:00:02.51">Now we do have a large amount of surface hardness data</p>
      <p begin="00:10:53.92" dur="00:00:01.19">from our synthetic turf plots</p>
      <p begin="00:10:55.12" dur="00:00:02.51">as well as some natural grass on our Web site</p>
      <p begin="00:10:57.63" dur="00:00:03.05">from a large study we have been conducting since 2001 –</p>
      <p begin="00:11:01.03" dur="00:00:02.47">again that is on our Web site and</p>
      <p begin="00:11:03.50" dur="00:00:03.02">that is the data from which we generated this equation.</p>
      <p begin="00:11:08.69" dur="00:00:02.02">So now that we know a little bit more about Gmax –</p>
      <p begin="00:11:10.79" dur="00:00:01.08">how we test for it,</p>
      <p begin="00:11:11.88" dur="00:00:01.12">what some of the numbers mean,</p>
      <p begin="00:11:13.30" dur="00:00:01.79">lets take a look at some of the advantages</p>
      <p begin="00:11:15.09" dur="00:00:01.46">of Gmax testing your field.</p>
      <p begin="00:11:17.40" dur="00:00:02.74">First of all we have that level of 200 Gmax,</p>
      <p begin="00:11:20.63" dur="00:00:01.88">and really a solid of 200</p>
      <p begin="00:11:22.52" dur="00:00:02.12">because that is based on safety studies –</p>
      <p begin="00:11:24.69" dur="00:00:02.99">there is science to back up that if you get above 200 g’s,</p>
      <p begin="00:11:27.80" dur="00:00:04.04">your risk of a severe head injury increases or is non-zero.</p>
      <p begin="00:11:33.17" dur="00:00:01.59">It also shows that you are being proactive</p>
      <p begin="00:11:34.77" dur="00:00:02.13">in your approach to safety of field users and</p>
      <p begin="00:11:36.90" dur="00:00:02.46">in turn it protects field owners from lawsuits –</p>
      <p begin="00:11:39.36" dur="00:00:01.28">when you can produce reports</p>
      <p begin="00:11:40.65" dur="00:00:03.18">that say look this met the ASTM standard of 200 or below,</p>
      <p begin="00:11:43.83" dur="00:00:02.66">that is going to go a long way in protecting yourself.</p>
      <p begin="00:11:47.40" dur="00:00:02.67">Now some other things to think about with Gmax testing</p>
      <p begin="00:11:50.07" dur="00:00:01.78">is we are not testing the entire field –</p>
      <p begin="00:11:52.33" dur="00:00:01.16">those test points were chosen</p>
      <p begin="00:11:53.49" dur="00:00:02.89">based on areas that were thought to be representative</p>
      <p begin="00:11:56.39" dur="00:00:01.01">of the whole field,</p>
      <p begin="00:11:57.79" dur="00:00:02.15">but in reality we are only testing 10 points</p>
      <p begin="00:12:00.10" dur="00:00:00.97">on a large field</p>
      <p begin="00:12:01.25" dur="00:00:01.70">so we are not getting a full understanding</p>
      <p begin="00:12:02.95" dur="00:00:01.23">of what is going on on that field.</p>
      <p begin="00:12:05.22" dur="00:00:02.98">There is also a cost associated with routine testing.</p>
      <p begin="00:12:08.87" dur="00:00:02.33">Certainly we can go back to that Clegg Impact Tester and</p>
      <p begin="00:12:11.21" dur="00:00:02.17">some field managers like to have that on hand –</p>
      <p begin="00:12:13.55" dur="00:00:02.14">they can monitor the field themselves and</p>
      <p begin="00:12:15.69" dur="00:00:03.33">then maybe every other year bring in an F355 test.</p>
      <p begin="00:12:20.05" dur="00:00:01.86">And finally the idea of the flat missile –</p>
      <p begin="00:12:21.92" dur="00:00:01.22">we talked about that earlier –</p>
      <p begin="00:12:23.33" dur="00:00:02.61">is that really the best way to represent a human head –</p>
      <p begin="00:12:25.95" dur="00:00:02.46">and obviously we can argue that it is not, however,</p>
      <p begin="00:12:28.44" dur="00:00:01.45">previous testing and</p>
      <p begin="00:12:29.89" dur="00:00:01.83">the way the ASTM standard was set up –</p>
      <p begin="00:12:31.73" dur="00:00:02.61">that is still the way that this testing is done and</p>
      <p begin="00:12:34.35" dur="00:00:01.82">in the future, that may change.</p>
      <p begin="00:12:38.17" dur="00:00:00.91">So as you can see</p>
      <p begin="00:12:39.09" dur="00:00:02.34">Gmax is an important characteristic of your field.</p>
      <p begin="00:12:41.86" dur="00:00:02.10">It is important to have your Gmax tested and</p>
      <p begin="00:12:43.96" dur="00:00:02.07">continually have that Gmax tested</p>
      <p begin="00:12:46.03" dur="00:00:01.20">so you can monitor</p>
      <p begin="00:12:47.24" dur="00:00:02.30">the surface hardness of your field over time.</p>
      <p begin="00:12:50.28" dur="00:00:01.57">I’d like to thank you for listening</p>
      <p begin="00:12:51.86" dur="00:00:01.67">to the latest addition of the Sportsturf Scoop.</p>
      <p begin="00:12:53.94" dur="00:00:02.86">Again, keep up to date with the latest research on our Web site,</p>
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