The self-insured employer appeals from the compensation judge’s determination that the employee sustained a work-related injury to his cervical spine on October 28, 2006.  We affirm.

Mr. Bernard R. Klug [the employee] has worked for Cummins Power Generation, Inc., [the employer], and its predecessor, since January 1973.  Throughout his tenure with the employer, the employee has worked in the logistics department.  In the warehouse area, the employee and his coworkers receive materials that are used in manufacturing generators.  They also deliver materials and parts throughout the plant and move the finished products to the shipping area.  In addition, as team leader, the employee performs inventory of parts in the warehouse, which includes reconciling or verifying each part number with each part stored within the warehouse.  The parts are stored on rows of vertical racks that range in height from 18 to 24 feet.  To perform the reconciling or inventory tasks, the employee typically looks up at the racks to locate a part number, and then uses one of three types of mechanical lifts to elevate him in the air so that he can reach for and pull the part that he needs to reconcile with his records.

On October 28, 2006, the employee was conducting this reconciliation of parts, and was reviewing tall parts that were stored on the top shelf.  While standing on one of the lifts called a “stand-up reach truck,” and as he looked up in the air, he immediately felt two “stingers” into both arms.  The employee described the sensation he felt as “numbness” extending through his arms.  He testified that he stepped off the reach truck, advised his coworkers what had happened, and then “just kind of walked it off” for five to ten minutes until his arms felt back to normal, or at least back to the point where he felt that he had “just pulled something.”  The employee testified that he did not immediately seek medical treatment as he only had a stiff neck and thought he perhaps had slept the wrong way on his neck.

On one occasion before this incident, the employee had consulted his treating physician for evaluation of neck pain.  On October 12, 2006, the employee consulted Dr. Reuben Lubka, at Columbia Park Medical Group.  Dr. Lubka’s chart note on October 12, 2006, reflects the employee’s history that his neck pain had extended back to at least August, if not longer, but that it had been worse for the past two weeks, and that the employee could recall no specific injury and had no complaints of pain shooting down his right arm.  Dr. Lubka diagnosed “severe cervical arthritis coupled with soft tissue inflammation/pain.”  He referred the employee for x-rays of his neck, which were interpreted as showing minor hypertrophic changes but no specific cause for pain.  Dr. Lubka commented in his chart note that “[t]here is the outside possibility that there is in fact some cervical disc disease and we will leave the door open for consideration of obtaining an MRI down the road.”

Dr. Lubka examined the employee again on November 14, 2006, to treat his essential hypertension.  His chart note of that date includes no reference to neck pain or to the October 28 incident.

The employee testified that after the October 28 incident, his left arm “was starting to go a little numb . . . once in a while.”  His symptoms became progressively worse, and he started to notice “a pin cushion effect” or “tingling” after Thanksgiving 2006.  The employee testified that he started noticing a sensation down his left arm, for an unknown reason, perhaps after “putting up Christmas lights or something like that,” and also testified that he could not remember what actually brought on his symptoms.  By the second week in December, his symptoms also extended into his right arm and into his leg,^[1] and by then were continuous in both arms.  According to the employee, these symptoms were different from those he had earlier reported to Dr. Lubka.

On December 18, 2006, the employee returned to Dr. Lubka, reporting numbness in both hands and intermittent and occasional neck pain that he had experienced for approximately two months.  An examination on that date showed decreased range of motion of the employee’s neck, and that when he fully extended his neck, he noted a “flash of pain” down his arms.  Dr. Lubka diagnosed bilateral upper extremity neuropathy which he felt was related to disc disease, and referred the employee for an MRI of the cervical spine to assess for possible severe central canal stenosis.  The MRI scan of the employee’s cervical spine, taken on December 19, 2006, showed significant degenerative disc findings and central and left paracentral broad-based disc herniation at C3-4 as well as lesser degrees of mild degeneration at a level above and three levels below the herniated disc.

Dr. Lubka referred the employee to Dr. Walter Galicich, neurosurgeon, who examined the employee on December 27, 2006, and concluded that the C3-4 disc herniation suggested a spinal cord injury and that the employee had sustained a “bruise” to his spinal cord.  Dr. Galicich recommended that the employee immediately proceed with a C3-4 anterior cervical discectomy and fusion; he performed that surgery on January 5, 2007 at Abbott Northwestern Hospital.

The employee testified that he received immediate although not total pain relief  from his surgery.  He remained off work for two months following surgery, at which time he returned to  work for the employer on a full-time basis.  While the employee remained off work, he received short-term disability benefits from his employer; his medical expenses were paid by his health carrier.  The employee felt his surgery was successful.  His left arm still occasionally tingles, especially when he “overdo[es] it,” but his right-sided sensation has dissipated.

On May 21, 2007, the employee filed a claim petition, which he later amended, seeking benefits related to his claimed injury of October 28, 2006.  In its answer to the employee’s claim petition, the employer denied primary liability for the claimed injury, asserting that the injury did not arise out of the employee’s employment.

In a letter dated May 11, 2007, Dr. Galicich outlined his opinion that the employee’s cervical spine surgery was necessitated by the employee’s cervical myelopathy due to his disc herniation and compression of the spinal cord.  Dr. Galicich concluded that

At the request of the employer, the employee underwent an independent medical examination with Dr. Edward W. Szalapski, Jr., an orthopedic surgeon.  Following his examination of the employee on October 9, 2007, Dr. Szalapski issued a report in which he concluded that the cause of the employee’s problem was strictly degenerative.  He explained that disc herniations commonly occur on a spontaneous basis and found it particularly notable that the employee had complained of neck symptoms approximately two and a half weeks before his claimed injury date of October 28, 2006, and that the employee’s symptoms admittedly had started back at least as early as August 2006.  Based on the employee’s medical records, Dr. Szalapski concluded that the employee had experienced a gradual evolution of his symptoms starting at least as early as August 2006, and that his contemporaneous medical records did not specify any incident happening at work.  He concluded as follows:

In a letter dated January 21, 2008, Dr. Lubka advised that he believed the employee’s condition to be related to his employment.  He acknowledged that the employee’s degenerative disc disease problem was a fairly common condition in persons over the age of 50, and that

The employee’s claims were addressed at a hearing on April 16, 2008.  At issue were the employee’s claims for temporary total disability benefits from December 26, 2006, through February 12, 2007; ongoing temporary partial disability benefits from that date; and payment of medical expenses related to his claimed injury of October 28, 2006.  The employee and a representative from the employer testified at the hearing; the employee’s medical records were submitted into evidence.  In her findings and order, served and filed June 16, 2008, the compensation judge determined that the employee’s cervical spine condition arose out of the employee’s employment on October 28, 2006.  The compensation judge found, in part, as follows:

In Minnesota, an injury is compensable for workers’ compensation purposes if the injury arises out of and in the course of the employee’s employment.  See Minn. Stat. § 176.011, subd. 16.  “In the course of” refers to the time, place, and circumstances of the injury, while “arising out of” refers to the causal connection between the injury and the employee’s work activity, although “not necessarily in the proximate cause sense.”  Gibberd v. Control Data Corp., 424 N.W.2d 776, 780, 40 W.C.D. 1040, 1047 (Minn. 1988); see also Lange v. Minneapolis-St. Paul Metro. Airport Comm’n, 257 Minn. 54, 99 N.W.2d 915, 21 W.C.D. 61 (1959).  The requisite causal connection “exists if the employment, by reason of its nature, obligations or incidents may reasonably be found to be the source of the injury producing hazard.”  Nelson v. City of St. Paul, 429 Minn. 53, 55, 81 N.W.2d 272, 275, 19 W.C.D. 120, 123 (1957).  Under what is known as the “increased risk” test, applicable in Minnesota, there must be a showing that the “injury was caused by an increased risk to which the claimant, as distinct from the general public, was subjected to by his or her employment.”  1 A. Larson & L.K. Larson, Workers’ Compensation Law § 3.00 (1999);  see Bohlin v. St. Louis County/Nopeming Nursing Home, 61 W.C.D. 69 (W.C.C.A. 2000); Pratt v. Minnesota Tax Invs., 63 W.C.D. 33 (W.C.C.A. 2005); Goebel v. Dyneon Corp./3M Co., No. WC04-243 (W.C.C.A. Jan. 24, 2005).

Whether an injury arose out of and in the course of employment is generally a fact question for the compensation judge, Franze v. National Delivery Serv., 49 W.C.D. 148, 155 (W.C.C.A. 1993), and the burden of proof is on the employee.  Minn. Stat. § 176.021, subd. 1.  In the present case, it is undisputed that the employee was in the course of his employment when he experienced symptoms in his neck.  That is, he was performing his usual work, during his usual shift, on the employer’s premises.  The employer contends, however, that there was an insufficient causal connection between the employee’s work activities and his cervical spine condition and need for treatment to support a finding of compensability.  In other words, the employer argues that the employee did not sustain an injury “arising out of” his employment.  The employer argues that even if the employee’s injury occurred at work, it did not rise to the level of a work-related injury, and the judge applied the wrong standard as she did not provide any analysis as to why the employee’s activity of “looking up” placed him at an increased risk of injury unique to the employee.

The employee testified that as he was working in the warehouse, he looked up in the air while pulling a part in the warehouse, and immediately felt “two stingers” go down his arms.  He also described that sensation as “numbness” going through his arms.  Dr. Lubka and Dr. Galicich both opined that the employee injured his neck as a result of his work activities.  Thus, there is evidence in the record that the medical cause of the employee’s neck injury was the employment activity of looking up at a tall shelf, while performing his work as a Team Leader in the employer’s logistics department.

It is the position of the employer that the mere act of looking up did not create a measurable increase in any risk to the employee.  We disagree.  We acknowledge that the act of looking up is an activity that persons often perform in the course of employment or as an ordinary activity outside of work.  In the vast majority of cases, however, the same can also be said of most employment-related physical activities.  There is no requirement that the work activity be unusual or strenuous, only that the injury follow as a natural incidence of the work.  Foley v. Honeywell, Inc., 488 N.W.2d 268 (Minn. 1992).  Because the employment required the employee to look up at parts stored on tall shelves, the compensation judge reasonably concluded that employee was subject to an increased risk distinct from that to which the general public is exposed.

The employer also argues that the judge referred to repeated incidents of the employee “looking up” at work, even though there was no such reference in the testimony, and that this  incorrect underlying assumption distorted the compensation judge’s perspective.  We disagree.  The employee testified about the nature of his work activities, including his reconciliation tasks that involved looking up at parts on shelves to read parts’ numbers.  Based on the employee’s testimony, and the testimony of the employer representative, it was not unreasonable for the compensation judge to infer that the employee’s work involved some repetition.  The compensation judge’s findings also include a reference to the sudden onset of the employee’s symptoms while he was looking up at parts; that reference is consistent with the employee’s testimony.

The compensation judge accepted the causation opinion of Drs. Lubka and Galicich.  The employer contends, however, the judge’s reliance on those medical opinions was legally erroneous because the doctors lacked foundation to opine the employee’s work activities caused his neck condition.  The employer argues the only factual basis for the doctors’ opinions is that the employee was at work, which is insufficient factual foundation for the opinions, and that the doctors’ unsupported conclusions should have been rejected by the compensation judge as lacking any probative value.

The employer specifically argues that Dr. Lubka’s opinions lack foundation as he never provided any indication of the facts upon which he relied in reaching his opinion that the employee’s condition was work-related.  The employer also contends that it is unclear whether Dr. Lubka had any actual knowledge of the employee’s injury and work activities, since his chart notes in November and December 2006 include no mention of the employee’s October 28, 2006, incident - - in sharp contradiction to his report of January 21, 2008, wherein he does mention an injury.  In addition, the employer argues that Dr. Galicich’s opinion lacks foundation, contending that Dr. Galicich did not appear to be aware of the employee’s neck problems prior to October 28, 2006.  It contends that neither of the doctors’ reports indicated that they were aware of the employee’s symptoms on October 28 and his later symptoms in November 2006 that precipitated his consultation with Dr. Lubka in December 2006, and that neither doctor explained why the employee would have been able to continue working following his October injury, without complaint and without seeking treatment until approximately seven weeks later.  We are not persuaded.

Dr. Lubka, the physician to whom the employee initially reported his neck symptoms, obtained a medical history from the employee, as reflected in his chart notes of October, November and December 2006.  Dr. Lubka ordered and reviewed diagnostic tests, and performed physical examinations.  Dr. Galicich, the employee’s treating surgeon, obtained a history from the employee, including a reference by the employee to earlier treatment for a stiff neck and muscle spasms in his neck.^[2]  He also conducted a physical examination of the employee, and reviewed the results of diagnostic testing.  As a general  rule, this level of medical expertise and practical experience establishes competency to render an expert medical opinion.  Reinhardt v. Colton, 337 N.W.2d 88 (Minn. 1983).

Dr. Lubka concluded that the employee’s work activity led to a rupture of a cervical disk and resulting bilateral upper extremity radiculopathy.  Dr. Galicich concluded that the employee’s act of looking upward was the cause of his disc herniation and resultant compression of the spinal cord.  We acknowledge that neither doctor itemized other records or information he reviewed in arriving at his opinion.  An expert medical opinion, however, does not lack foundation because the doctor fails to explain the underlying reasons for his expert opinion.  Rather, the presence or absence of such testimony or explanation goes only to the weight that may be afforded the opinion by the compensation judge.  In this case, competent medical witnesses opined that the employee’s injury causally contributed to the disabling condition.  See, e.g., Midtling v. Schwan’s Sales Enters., slip op. (W.C.C.A. Sept. 22, 2003).  Dr. Lubka’s and Dr. Galicich’s opinions were adequately founded and the compensation judge reasonably relied upon those opinions.  Because the compensation judge’s findings are supported by substantial evidence in the record, including medical records and opinions, we affirm the findings in their entirety.