The employee appeals from an arbitrator’s decision concluding that the employee failed to prove he sustained a personal injury on October 13, 2006, arising out of his employment, and that the employee failed to give notice of a personal injury within 180 days of October 13, 2006.  We affirm.

Mark G. Schweich, the employee, was employed by Phillippi Equipment Services, the employer, on October 13, 2006.  The employer was then self-insured for workers’ compensation liability.  On that date, the employee contends he sustained a personal injury to his low back arising out of and in the course of his employment.

The employee had a history of low back complaints and treatment prior to October 13, 2006.  The employee treated extensively from December 1990 through July 1991 with Wayne Dahl, D.C.  In July 2002, the employee returned to see Dr. Dahl complaining of low back pain.  The employee gave a history of back pain for the last 18 or 19 years with a recent onset on July 13, 2002.  The employee complained of constant, moderate, bilateral low back pain worsened by turning, lifting, and bending.  In response to a written question about the mechanism of the onset, the employee wrote, “everyday/job related - no specific work injury.”  Dr. Dahl commenced a series of chiropractic treatments which continued through May 1, 2003.  On that date, the employee complained of continuing low back complaints.  On examination, Dr. Dahl noted continuing spasm and pain in the lower back with tenderness and loss of range of motion in the lumbosacral junction.  Thereafter, the employee treated with Anthony B. Hass, D.C., in 2003 and 2004 for lumbosacral pain.  On July 31, 2004, Dr. Hass noted a moderate level of lumbosacral pain on palpation, paraspinal muscle tenderness, and diagnosed a sacroiliac and L4 subluxation.  At some point, the employee began treating with David Galleberg, D.C.  A lumbar x-ray ordered by Dr. Galleberg on March 17, 2005, was read as showing a mild rightward curvature of the mid-lumbar spine with degenerative joint disease at L4-5 and 1 cm of anterolisthesis of L4 and L5.  The employee treated with Dr. Galleberg nearly weekly from March 2005 through September 2006, including treatments on September 18 and 22, 2006.

The employee saw Dr. James Laskow at Northern Shores Chiropractic on October 20, 2006.  The employee testified he saw Dr. Laskow because Dr. Galleberg was unavailable.  The doctor asked the employee the reason for his visit and the employee testified he told the doctor that he jumped off a crane the previous Friday resulting in back pain.  On a history form prepared by the employee, the doctor wrote in “jumped off crane.”  Dr. Laskow instituted chiropractic treatment.  Dr. Laskow referred the employee for an MRI scan of the lumbar spine which was obtained in January 2007.  The impression was Grade I/II spondylolytic spondylolisthesis of L4, advanced degenerative disc space narrowing at L4-5, and right nerve root canal stenosis with impingement on the left L5 nerve root.

The employee returned to see Dr. Galleberg on November 1, 2006.  On that date, the doctor rated the employee’s condition as mild.  On November 9, 2006, the employee reported pain in the thoracic region which the doctor noted came on over the last 3 to 4 days.  The employee also treated with Dr. Galleberg on November 10 and November 22, 2006.  In none of the doctor’s notes is there a reference to an incident or injury on October 13, 2006.

On January 16, 2007, the employee saw Dr. Anthony G. Bottini, a neurosurgeon, on referral from Dr. Laskow.  The employee did not tell Dr. Bottini about the alleged work injury of October 13, 2006.  In his consultation report, the doctor recorded the following history of present illness:

The employee returned to see Dr. Bottini on May 14, 2007, with “a number of questions regarding Workmens’ Compensation portion of his problem.”  In his report, Dr. Bottini stated, “We also looked at additional paperwork which the patient needs to submit for his union-based disability insurance.  This will be completed and forwarded back to him.  Patient inquired regarding documentation of the mechanism of injury.  He tells me today that he believes that the symptoms in his back began after he jumped off a crane in the Burnsville area.  He did not share this information at the time of initial consultation and thus it was not documented at that time.”  (Pet. Ex. A.)  By report dated August 13, 2008, Dr. Bottini opined the employee had reached maximum medical improvement on February 11, 2008, and rated a permanent disability of 17%.  In that report, Dr. Bottini opined the employee’s injury was caused, aggravated, or accelerated by employment activity.

By report dated June 19, 2007, Dr. Laskow stated, in part:

The employee filed a claim petition alleging that he sustained an injury arising out of his employment on October 13, 2006, and claiming entitlement to wage loss benefits, medical benefits, and rehabilitation benefits.  The employer denied the employee sustained a personal injury and denied liability for the claimed benefits.  Pursuant to a collective bargaining agreement between the employee’s union and the employer, work-related-injury disputes are to be resolved through an alternative dispute resolution system under Minn. Stat. § 176.1812 (2002).

At the request of a representative of the Union Construction Workers’ Compensation Program, Dr. David Florence performed a dispute resolution examination of the employee on July 10, 2008.  The doctor obtained a history from the employee, reviewed medical records, and examined the employee.  The employee told the doctor that he injured his low back on October 13, 2006, when he jumped off a crane, landed flat footed, and had immediate pain in his low back.  The doctor diagnosed low back and left leg pain without objective radiculopathy, status post fusion and laminectomy at L4-5 and multilevel lumbar facet arthrosis.  The doctor reviewed an x-ray taken on August 17, 2005, that showed the employee had a mild rightward curvature of the mid-lumbar spine, a component of multilevel facet joint degenerative changes of the lower lumbar spine, and a 1 cm anterolilisthesis of L4 on L5.  Dr. Florence concluded the medical records documented a significant preexisting lumbar degenerative condition.  The doctor also reviewed the January 3, 2007, MRI scan which confirmed the Grade I-II spondylolisthesis of L4 with longstanding lateral pons deficits, a 25% anterolisthesis of L4, advanced degenerative disc disease and instability at L4-5.  Dr. Florence opined the 2007 MRI report was very similar to the 2005 x-ray report.  Assuming the history he obtained regarding the October 13, 2006, incident was accurate, Dr. Florence opined the incident was a substantial contributing factor in accelerating and aggravating the employee’s preexisting back condition resulting in disability and need for treatment.  If the history was not accurate, the doctor opined the incident did not cause any injury, permanent or temporary.  Dr. Florence assigned restrictions, opined the employee was not capable of returning to unrestricted work as an operating engineer, and rated a permanent partial disability of 15% of the whole body.

A hearing was held before an arbitrator in December 2008.  The employee testified that he went to work for the employer in September 2006 as an oiler.  His duties included lubrication, maintenance, and set-up of a mobile crane.  The employee testified that on the morning of October 13, 2006, he and Terry Wurtz, the crane operator, picked up a crane in Blaine and drove it to a jobsite in Burnsville, Minnesota.  At some point as he was setting up the crane for operation, the employee climbed up onto a leg of the crane, called an outrigger, and then jumped to the ground.  When he did so, the employee testified he landed on both of his feet, his knees hit the ground, and he experienced immediate, intense low back pain with numbness in his left leg.  The employee testified that at their 9:00 a.m. break, Mr. Wurtz asked the employee why he was limping and the employee described the incident of jumping down from the outrigger.  Prior to lunchtime, the employee asked Mr. Wurtz if he had any medication and was given some Tylenol out of a black, round container.

Terry Wurtz testified he and the employee met at the employer’s Eagan location, then went to Blaine to pick up a crane, and then drove to Burnsville to set up the crane.  He stated they did not arrive at the Burnsville site until 1:30 or 2:30 in the afternoon.  Mr. Wurtz denied seeing the employee jump off the outrigger and denied giving the employee Tylenol.  Mr. Wurtz testified he carried chewing tobacco not Tylenol in a black round container.  Mr. Wurtz testified that at no time during that day did he see the employee limp.  Mr. Wurtz testified that had he seen an oiler limping, he would have asked what happened, asked them to report the injury, or reported it himself.

On October 18, 2006, the employee brought some deer horns into the office to show people.  The employee testified, Cory, one of the office managers, asked him about his limp.  The employee testified he told Cory he hurt himself the previous Friday while setting up a crane.  Cory Dauner testified he was a dispatcher for the employer in October 2006.  He testified he talked to the employee about the deer horns he brought in, but denied he saw the employee limping and denied the employee told him he was injured on the job.  Had the employee told him he was injured at work, Mr. Dauner stated he would have prepared a report of injury or referred him to Mr. Corcoran.  Jerome Corcoran, the controller for the employer, stated he first received notice that the employee was claiming a personal injury on April 19, 2007, in a phone call from the employee.  Mr. Corcoran then prepared a first report of injury.

The employee testified that on Friday, October 20, 2006, he worked a short day in the St. Peter, Minnesota, area and then stopped by the employer’s office to check his mailbox to see what his next job duties would be.  The employee stated he was unable to bend because of back pain and had to drop to his knees to open up his mailbox.  The employee testified that Robin, the office manager, saw him limping, saw him kneel to get into his mailbox, and asked what was wrong.  The employee told Robin he had hurt his back jumping off an outrigger on the Burnsville job.  Robin did not testify at the hearing.  The records of the employer reflect the employee did not work on October 20, 2006.

Dean O’Brien, a taxidermist, testified he first met the employee on September 24, 2006, when the employee came with a deer on the top of his vehicle.  The employee asked Mr. O’Brien about mounting the antlers.  On September 25, the employee returned with just the head of the deer, which the employee carried in to Mr. O’Brien’s shop.  The employee returned on September 29 to pick up the mounted antlers.  Mr. O’Brien testified that on none of those occasions did he see the employee limp or display any obvious signs of pain or discomfort.  Several weeks later, the employee returned and Mr. O’Brien testified he observed a dramatic change in the employee’s condition.  Mr. O’Brien testified that the employee walked and acted like Mr. O’Brien did when he had an injured back.  He described the employee as being very stiff and slow moving and unstable in his movements.

The employee continued to work for the employer without loss of time until he was laid off on November 10, 2006.  The employee then filed for unemployment benefits.

The employee underwent an MRI scan on January 3, 2007.  On January 4, the employee called Deborah Johnson, a claims examiner at Wilson McShane Co., the company that handles medical and disability claims for the International Union of Operating Engineers.  Ms. Johnson testified the employee stated his back pain and need for the MRI scan was not due to a work injury.  Ms. Johnson then prepared a computer note which stated, in part, “not auto or WC related.  He has had back pain, had an MRI done 1-07 and might need back surgery” (Resp. Ex. 6).  On May 2, 2007, Ms. Johnson prepared a computer note after talking to the employee which refers to a claimed injury on October 16, 2006, for “jumping out of a crane at Blmgtn job” (Resp. Ex. 6).

Theresa Lawrence testified she lived with Mr. Schweich from April 2003 through August 2008.  Between April 2003 and October 2006, she did not recall the employee ever missing significant periods of time from work because of back problems.  Ms. Lawrence testified she helped the employee load the deer onto the car in September 2006 and, after the employee returned from the taxidermist, helped him skin the deer.  At no time during that process did the employee complain to Ms. Lawrence about back pain.  On or about October 13, 2006, Ms. Lawrence testified the employee was “real pale and in severe pain” when he came home from work.  The employee told Ms. Lawrence he had to jump down off a crane and injured his back.  The employee spent the weekend after his injury in bed or sitting on the couch.  Ms. Lawrence told the employee to go to the doctor, but the employee stated he had no insurance.

Following the hearing, the arbitrator issued an Amended Arbitrator’s Award in which he concluded the employee failed to sustain his burden of proving that he sustained a personal injury on October 13, 2006, arising out of his employment with the employer.  The arbitrator further found the employee failed to give notice of a personal injury within 180 days of October 13, 2006.  Accordingly, the arbitrator denied the employee’s claims for benefits.  The employee appeals.

The employee argues the arbitrator’s decision is unsupported by substantial evidence and ignores substantial evidence in the record that the employee sustained a personal injury on October 13, 2006.  First, the records of the Northern Shore Chiropractic Clinic clearly mention an incident in which the employee jumped off a crane.  This record is the one closest in time to the October 13, 2006, incident.  Dean O’Brien testified that he saw the employee on three occasions in September and he was not limping.  Approximately three weeks later, Mr. O’Brien testified the employee displayed obvious signs of low back problems.  Ms. Lawrence, the employee’s former girlfriend, also testified to a change in the employee’s low back condition after October 13, 2006.  The employee contends both Mr. O’Brien and Ms. Lawrence are unbiased witnesses, each of whom confirms the employee’s testimony.  The employee acknowledges he did not tell Dr. Bottini about the October 13, 2006, work injury.  But the employee testified he assumed the treatment notes from Dr. Laskow would be forwarded to Dr. Bottini so it would not be necessary for him to repeat that history.  Finally, the employee contends the opinion of Dr. Florence, that the October 2006 incident was a substantial contributing factor in accelerating the employee’s preexisting back condition was ignored by the arbitrator.  For these reasons, the appellant contends the arbitrator’s decision should be reversed.

As this court has stated on many occasions, assessment of witness credibility is the unique function of the fact finder.  Tews v. Geo. A. Hormel & Co., 430 N.W.2d 178, 41 W.C.D. 410 (Minn. 1988).  Where evidence is conflicting or more than one inference may reasonably be drawn from the evidence, the findings of the fact finder are to be upheld.  Redgate v. Sroga's Standard Serv., 421 N.W.2d 729, 734, 40 W.C.D. 948, 957 (Minn. 1988).  The issue in this case is whether the decision of the arbitrator is supported by substantial evidence.

There is substantial, credible evidence in the record to support the employee’s claim that he sustained a personal injury arising out of his employment on October 13, 2006.  This evidence includes the records and reports of Dr. Laskow and Dr. Bottini, together with the testimony of the employee, Ms. Lawrence, and Mr. O’Brien.  Under this court’s standard of review, however, the issue is not whether the evidence will support alternative findings, but whether substantial evidence supports the decision.  In applying this standard, this court looks not only at the evidence that supports the arbitrator’s findings, but also at the opposing evidence and the evidence from which conflicting inferences might be drawn.  The evidence, in a sense, must be weighed to determine its substantiality.  The substantial evidence standard “is an admonition to the reviewing court not to treat the findings of the fact finder lightly, while at the same time the reviewing court remains cognizant of its own responsibility to exercise good judgment in reviewing what the evidence will reasonably sustain.”  Hengemuhle v. Long Prairie Jaycees, 358 N.W.2d 54, 59, 37 W.C.D. 235, 239 (Minn. 1984).  In this case, we conclude there is substantial evidence in the record to support the arbitrator’s decision.

The employee claimed Mr. Wurtz and Mr. Dauner saw the employee limping, asked him about his condition, and were told he hurt his back jumping off an outrigger on October 13, 2006.  Both Mr. Wurtz and Mr. Dauner denied knowledge of any injury to the employee.  Ms. Johnson testified that when she spoke with the employee on January 4, 2007, regarding payment for the employee’s MRI scan, the employee denied the need for the scan was due to a work injury.  Mr. Corcoran testified he first received notice of the claimed injury in a phone call from the employee on April 19, 2007.  The employee has a significant history of preexisting low back problems dating back at least to 1990.  In July 2002, the employee gave Dr. Dahl a history of low back pain for the last 18 or 19 years.  The employee treated nearly weekly with Dr. Galleberg from March 2005 through September 2006, including treatments on September 18 and September 22, 2006, just a month before the claimed injury.  The employee did not seek medical treatment until a week after the claimed injury when he saw Dr. Laskow.  The history form prepared by Dr. Laskow does reflect an incident where the employee jumped off the crane.  While the doctor’s handwriting is difficult to decipher, it appears the doctor recorded this incident as happening three weeks previously.  When he saw Dr. Galleberg on November 1, 2006, the doctor’s records make no mention of an incident on October 13 when the employee jumped off a crane.  Further, on that date, the doctor noted the employee’s condition as mild.  Neither did the employee give Dr. Bottini a history of the October 13, 2006, incident when the employee saw him in January 2007.  Dr. Florence compared a 2005 x-ray with the 2007 MRI scan and concluded they were very similar.

From the foregoing evidence, the arbitrator could reasonably conclude either that the October 13, 2006, incident did not occur or that if it did, the incident did not substantially aggravate or accelerate the employee’s preexisting low back condition.  Factual findings are clearly erroneous only if this court, based on a review of the record as a whole, is left with a definite and firm conviction that a mistake has been committed.  Northern States Power Co. v. Lyon Food Prods., Inc., 304 Minn. 196, 201, 229 N.W.2d 521, 524 (1975).  In this case, we cannot conclude that the arbitrator erred.  Rather, we find that substantial evidence supports the arbitrator’s decision and must, therefore, be affirmed.^[1]