KENNETH L. BUETTNER, Presiding Judge.

¶ 1 Petitioner/Counter-Respondent Jeffery Blaine Harvey (Claimant) appeals an order of a three-judge panel of the Workers' Compensation Court affirming the trial court's order. Claimant asserts that Respondents/Counter-Petitioners Auto Plus of Woodward and Acadia Insurance Company (collectively, Employer) waived a defense based on 85 O.S.Supp.2010 § 11(B)(5),1 because it was not specifically pleaded in a Form 10. Employer counter-appeals and argues that the finding of compensable injury is against the clear weight of the evidence because Claimant was injuriously exposed to the cumulative trauma for a period of more than ninety (90) days in his subsequent employment. We hold that the § 11(B)(5) defense was not waived, and the finding of compensable injury was not against the clear weight of the evidence. The order of the three-judge panel is SUSTAINED.

FACTS

¶ 2 Claimant worked for Employer for nine years installing car windows. Claimant filed a Form 3 April 2, 2010, alleging cumulative trauma injuries to both hands, both arms, both shoulders, and spine from pounding windows with his hands and using vibrating hand tools. Claimant continued to work for Employer after he filed his Form 3. The owner of Employer died, and the business closed May 28, 2010. Claimant alleged the last date of exposure was May 28, 2010. After Employer closed, Claimant opened and operated his own car window installation business, Max Auto Glass, at the same location.

¶ 3 Employer denied compensability, and the trial court appointed Dr. Richard Ruffin as the Independent Medical Examiner October 29, 2010. Claimant filed a Form 9 Motion for Trial seeking medical treatment and surgical authorization March 31, 2011. Employer requested that Claimant be evaluated by Dr. Kent C. Hensley. Dr. Hensley evaluated Claimant April 28, 2011 and issued a report finding no cumulative trauma and noting that if work with Employer was injurious, then work in subsequent employment was also injurious. Dr. Hensley's report was provided to Claimant a few days before trial. Employer filed a Form 10 and asserted the affirmative defense of subsequent aggravation May 4, 2011, one day before trial.

¶ 4 The case proceeded to trial May 5, 2011. At trial, Employer raised a § 11(B)(5) defense and argued Claimant's subsequent employer should be liable for benefits. Claimant argued Employer waived the defense, because it was not specifically pleaded on a Form 10. On May 9, 2011, the trial judge issued an order finding Claimant sustained compensable cumulative trauma injuries to his hands, wrists, arms, and elbows. The trial court rejected Claimant's argument that the § 11(B)(5) defense was waived and noted that the defense was adequately explored during Claimant's deposition, Dr. Ruffin's deposition, and by pleadings on file as of the day of trial. However, the trial court denied Employer's defense of subsequent aggravation and found "Claimant has not suffered injurious exposure as a self employed person (work dropped off)." The trial court continued to say that Employer's "85 O.S. § 11(b)(5) defense is DENIED based on DR. RUFFIN'S deposition of MARCH 8, 2011 and based on claimant's testimony about reduced tasks and a change in tasks following employer's death." Both parties sought review from a three-judge panel. The three-judge panel affirmed the decision of the trial court. Both parties now seek review of the order of the three-judge panel. The Supreme Court of Oklahoma issued an order consolidating review proceedings for Case No. 109,803 and Case No. 109,805 under surviving Case No. 109,803.

STANDARD OF REVIEW

¶ 5 First, we must determine the proper standard of review. Claimant argues the any competent evidence standard of review applies, because the injury occurred prior to the effective date of 85 O.S.2011 § 340(D). Employer argues this Court should determine whether the panel's findings were against the clear weight of the evidence, as set forth in 85 O.S. § 340(D). Claimant and Employer filed their petitions for review August 26, 2011, the same day 85 O.S. § 340(D) went into effect. The 2011 amendment to the Workers' Compensation Code provides:

85 O.S. § 340(D). Despite recent amendments to the Workers' Compensation Code and multiple decisions from appellate courts, uncertainty pervades. Clarification of the proper standard of review is warranted.2 The issue presented is whether the standard of review established in 85 O.S.2011 § 340(D) applies when an appeal was filed after the new statute went into effect, but the claimant's injuries occurred and the matter was tried prior to the effective date of the statute. We hold that it does.

¶ 6 Prior to the 2010 amendment to 85 O.S. § 3.6, the standard of review was different depending on whether the review was by a three-judge panel of the Workers' Compensation Court or by the Supreme Court. In Parks v. Norman Municipal Hospital, 1984 OK 53, 684 P.2d 548, the Supreme Court of Oklahoma held that while the three-judge panel reviews the trial judge's findings to determine if they are against the clear weight of the evidence, the Supreme Court applies the any competent evidence standard when reviewing the panel's decision. Id. at 549 (applying 85 O.S.1981 § 3.6(A)).3 The Court also applied the any competent evidence standard of review to appeals from decisions of individual judges of the Workers' Compensation Court. Prior to the 2010 amendment, "[o]nly in the absence of competent evidence [would the] tribunal's decision be viewed as legally erroneous and hence subject to appellate vacation." Yocum v. Greenbriar Nursing Home, 2005 OK 27, ¶ 8, 130 P.3d 213, 218-219.

¶ 7 The 2010 amendment to 85 O.S. § 3.6(C) provided:

85 O.S.Supp.2010 § 3.6(C) (repealed). The 2010 amendment took effect November 1, 2010 and authorized the Supreme Court to review an order or award to determine whether it was against the clear weight of the evidence. In Dunlap v. Multiple Injury Trust Fund, 2011 OK 14, 249 P.3d 951, the Supreme Court held that the against the clear weight of the evidence standard of review set out in 85 O.S.Supp.2010 § 3.6(C) applied prospectively to claims for injuries that occurred after the effective date of the amendment, i.e., November 1, 2010. Id. ¶ 1, 249 P.3d at 952. As for appeals in cases where the injury underlying the claim for benefits occurred prior to the effective date of the amendment, the any competent evidence standard of review applied. Id.

¶ 8 In direct response to the Court's decision in Dunlap, the Oklahoma Legislature again amended and renumbered § 3.6(C), adding the language: "After the effective date of this act, regardless of the date of injury ..." 85 O.S.2011 § 340(D), effective August 26, 2011. All other language from the 2010 statute remained the same.

¶ 9 Claimant asserts that despite 85 O.S. § 340(D), the law in effect at the time of the injury should apply. Claimant's date of last exposure was May 28, 2010. On that day, any competent evidence was the standard of review. Claimant first argues that the Legislature's attempt at instructing the Oklahoma Supreme Court on the standard of review in § 340(D) is invalid under the separation of powers doctrine and violates Article IV, § 1 of the Oklahoma Constitution. Employer argues that standards of review are established by either appellate practice or explicit statutory command and, therefore, the Legislature is permitted to establish the standard of review for a particular matter.

¶ 10 Article IV, § 1 of the Oklahoma Constitution provides:

OKLA. CONST. art. IV, § 1. Every legislative act is presumed to be constitutional and will be upheld unless it is clearly, palpably, and plainly inconsistent with the Constitution. City of Edmond v. Vernon, 2009 OK CIV APP 36, ¶ 8, 210 P.3d 860, 863 (citing Mehdipour v. State ex rel. Dep't of Corr., 2004 OK 19, ¶ 22, 90 P.3d 546, 555). The burden is on Claimant, as the party challenging the statute, to show beyond a reasonable doubt that § 340(D) is unconstitutional. See City of Enid v. Public Employees Relations Bd., 2006 OK 16, ¶ 5, 133 P.3d 281, 285. This burden has not been met, and we hold that 85 O.S. § 340(D) does not violate the Constitution.

¶ 11 Claimant has failed to cite a single case where the Oklahoma Supreme Court or Court of Criminal Appeals determined a statutorily prescribed standard of review was unconstitutional because it violated the separation of powers doctrine, and we have yet to discover such case.4 To the contrary, the Legislature has established standards of review for particular matters in numerous statutes.5 Furthermore, the Supreme Court of Oklahoma and the Court of Criminal Appeals have commonly applied these statutorily prescribed standards of review.6 The United States Supreme Court has acknowledged the viability of statutorily prescribed standards of review. In Pierce v. Underwood, 487 U.S. 552, 108 S.Ct. 2541, 101 L.Ed.2d 490 (1988), the Court recognized:

Id. at 558, 108 S.Ct. 2541 (emphasis added). The against the clear weight of the evidence standard of review prescribed in 85 O.S. § 340(D) is an explicit statutory command. The Supreme Court of Oklahoma has acknowledged that the Legislature often expressly sets forth the standard of review in statutes. See Estrada v. Port City Properties, Inc., 2011 OK 30, ¶ 19, 258 P.3d 495, 504 n. 29 ("Although the statute has no express provision for review of a punitive damages award, the Court does review such award as safeguards against excessive verdicts."). We are not persuaded by Claimant's unsupported argument that statutorily prescribed standards of review violate the separation of powers doctrine of the Oklahoma Constitution.

¶ 12 Alternatively, Claimant argues that even if the statute is constitutional, it cannot be applied retroactively to cases that have previously been tried to a trial court and reviewed by a three-judge panel, because the amendment affects the substantive rights of the parties. Employer responds and argues that the clear language of the 2011 amendment evidences the Legislature's intent that Oklahoma appellate courts apply the against the clear weight of the evidence standard of review retroactively. Employer further suggests that the standard of review is a matter of procedure and, therefore, may be applied retroactively.

¶ 13 The Supreme Court of Oklahoma summarized the long-standing principles regarding the retroactive and prospective application of statutes in Cole v. Silverado Foods, Inc., 2003 OK 81, 78 P.3d 542. The Court stated:

Id. ¶ 8, 78 P.3d at 546 (footnotes omitted) (emphasis original). In CNA Insurance Co. v. Ellis, 2006 OK 81, 148 P.3d 874, the Oklahoma Supreme Court determined that 85 O.S.2001 § 11(B)(5) could not be given retroactive effect because the statute affected the substantive rights of the parties. The Court noted:

Id. ¶¶ 12-14, 148 P.3d at 877 (citations omitted). The Court in Cole and CNA suggests that a statute will be given retroactive effect if the Legislature clearly expresses its intent to do so, and retroactive application does not affect the substantive rights of the parties.

¶ 14 The Legislature clearly expressed its intent that § 340(D) was to be applied retroactively when it amended the statute to include the language: "After the effective date of this act, regardless of the date of injury, the Supreme Court may modify, reverse, remand for rehearing, or set aside the order or award [if] ... [t]he order or award was against the clear weight of the evidence." 85 O.S.2011 § 340(D) (emphasis added). The Supreme Court in Dunlap held that the against the clear weight of the evidence standard of review established in 85 O.S.Supp.2010 § 3.6(C) did not apply to appeals where the injury underlying the claim occurred prior to the effective date of the 2010 amendment. However, Dunlap interpreted the 2010 statute, which did not contain plain language expressing the Legislature's intent to apply the statute retroactively. The Legislature amended the statute in 2011 by adding plain language expressing its intent that § 340(D) is to be applied retroactively.

¶ 15 Furthermore, generally the standard of review is a matter of procedure and, therefore, may be applied retroactively without affecting the substantive rights of the parties. Although the Oklahoma Supreme Court has not specifically ruled on whether standards of review are procedural or substantive, several other jurisdictions have determined standards of review are procedural and may be applied retroactively.7 The Oklahoma Legislature amended the class certification statute in 2009. See 12 O.S.Supp.2009 § 2023(C). The 2009 amendment to 12 O.S. § 2023 established de novo review of class certification orders.8 In Gentry v. Cotton Electric Cooperative, Inc., 2011 OK CIV APP 24, 268 P.3d 534, the Court of Civil Appeals held that the de novo standard of review prescribed in the amended statute applied retroactively. Id. ¶ 10, 268 P.3d at 539. The court explained that CEC failed to show that the standard of review was substantive rather than procedural and, therefore, the standard of review applied retroactively. Id. ¶ 8, 268 P.3d at 538. The court noted that "when constitutional rights are at issue, the correct standard of review will be applied in pending cases even though a different standard had been previously used" and found no reason to apply a different rule when non-constitutional rights are at issue. Id. ¶ 9, 268 P.3d at 539.9

¶ 16 We are not persuaded by Claimant's argument that if one party prevails at trial under the any competent evidence standard of review but loses when the against the clear weight of the evidence standard of review is applied on appeal, the standard of review has affected the party's substantive rights. The standard of review prescribed in § 340(D) does not alter the burden of proof at trial. It remains that the employee has the burden of proof to establish by a preponderance of the evidence that the injury was caused by the employment. See 85 O.S.2011 § 308(10)(a). Furthermore, Claimant was subject to the clear weight of the evidence standard of review when he sought review from the three-judge panel. Prior to the 2011 amendment, a three-judge panel of the Workers' Compensation Court could reverse or modify the trial judge's decision only if it determined that the decision was against the clear weight of the evidence or contrary to law. See 85 O.S.Supp.2010 § 3.6(A); Parks, 1984 OK 53, 684 P.2d at 549.

¶ 17 Our determination of the proper standard of review is consistent with Division 2 and Division 4 of the Court of Civil Appeals. Division 2 applied the against the clear weight of the evidence standard of review in Okla. Dep't of Mental Health & Substance Abuse v. Pierce, 2012 OK CIV APP 73, ¶ 14, 283 P.3d 894. The Pierce court noted that "[t]he standard of review in effect when this appeal was ready for decision [was] that provided in the 2011 amendment." Id. Division 4 applied the against the clear weight of the evidence standard of review in McGuire v. N. Glantz & Sons LLC, 2012 OK CIV APP 59, ¶ 9, 278 P.3d 1060, 1061. In McGuire, the claimant's petition for review was commenced August 30, 2011, after the August 26, 2011 effective date of 85 O.S. § 340(D).

¶ 18 We hold that the Legislature clearly expressed its intent that 85 O.S. § 340(D) be applied retroactively and that the statute does not affect the substantive rights of the parties. Therefore, § 340(D) provides the proper standard of review for this appeal.10 We will affirm the decision of the three-judge panel unless the order or award is contrary to law or against the clear weight of the evidence. 85 O.S. § 340(D).

85 O.S. § 11(B)(5) DEFENSE NOT WAIVED

¶ 19 Claimant appeals the finding that Employer had not waived its § 11(B)(5) defense. Claimant argues the defense was waived because Employer did not specifically plead the affirmative defense in a Form 10. Claimant relies on Workers' Compensation Court Rule 16:

Rule 16(B)(2), Rules of the Workers' Compensation Court, 85 O.S.Supp.2006, Ch. 4, App. (emphasis added). Claimant asserts that because Employer did not timely file a Form 10, it waived the subsequent aggravation defense. Rule 19 provides:

Rule 19, Rules of the Workers' Compensation Court, 85 O.S.Supp.2006, Ch. 4, App. (emphasis added). Claimant filed his Form 9 March 31, 2011. Employer filed a Form 10 November 9, 2010, but no affirmative defenses were asserted. It was not until May 4, 2011, one day before trial, that Employer filed a Form 10 and asserted subsequent aggravation as an affirmative defense.

¶ 20 Employer responds that its § 11(B)(5) defense was not a surprise to Claimant, and the trial court found good cause for excusing the failure to assert an affirmative defense in a timely filed Form 10 when it stated in the order that the § 11(B)(5) defense "was adequately explored during claimant's deposition, DR. RUFFIN'S deposition and by pleadings on file as of the day of trial." Employer asserts that strict adherence to Rules 16 and 19 is not required as the Workers' Compensation Court has the authority to relax rules within its discretion.

¶ 21 We hold that it was within the trial court's discretion to allow Employer to assert the § 11(B)(5) defense even though it did not strictly comply with Rules 16 and 19. The Workers' Compensation Court has the authority to adopt rules and the authority to relax them within its discretion. Arrow Trucking Co., Inc. v. Jimenez, 2010 OK CIV APP 9, ¶ 23, 231 P.3d 741, 748 (citing Ed Wright Constr. Co. v. McKey, 1979 OK 25, 591 P.2d 302). Furthermore, the trial court may implicitly excuse strict compliance with court rules for good cause.11 When the trial court found the defense had not been waived because it had been adequately explored during discovery, the court implicitly excused compliance for good cause. Therefore, the trial court did not err in finding Employer had not waived its § 11(B)(5) defense.

DENIAL OF 85 O.S. § 11(B)(5) DEFENSE WAS NOT AGAINST THE CLEAR WEIGHT OF THE EVIDENCE

¶ 22 Employer appeals the denial of its § 11(B)(5) defense. Employer argues that finding a compensable injury is against the clear weight of the evidence because Claimant was injuriously exposed to the trauma in his subsequent employment for a period of more than ninety (90) days. Employer asserts that Claimant's subsequent employer is liable for any and all benefits. Title 85, § 11(B)(5) provides:

85 O.S. § 11(B)(5). Employer suggests that Claimant was self-employed at Max Auto Glass for more than ninety (90) days, and Claimant admitted that while self-employed, he pounded windows with his hands and used vibratory tools. Employer further relies on Dr. Hensley's report and Dr. Ruffin's deposition. Dr. Ruffin testified that Claimant's subsequent employment aggravated or maintained his condition. Employer asserts that after Claimant became self-employed, he continued to be exposed to the trauma that caused or contributed to his injury; therefore, Max Auto Glass should be liable for the compensation payable for an injury resulting from the cumulative trauma.

¶ 23 Claimant argues that he was not "injuriously" exposed to the trauma during subsequent employment. Claimant claims he significantly reduced his exposure to vibrating hand tools after becoming self-employed and, therefore, his exposure to the trauma was not "injurious." Claimant also relies on his own testimony at trial and Dr. Ruffin's deposition testimony. Dr. Ruffin testified that the need for surgery existed prior to Claimant becoming self-employed and that subsequent employment did not make Claimant's injury worse. Claimant also suggests Employer should have joined Max Auto Glass to the claim.

¶ 24 The Court of Civil Appeals has considered similar facts in Southern Material Handling Co. v. Falling, 2006 OK CIV APP 81, 138 P.3d 838, and Neel v. Am. Woodmark Corp., 2006 OK CIV APP 66, 136 P.3d 732. In Falling, the claimant alleged cumulative trauma injuries to his shoulder, arm, and hands. 2006 OK CIV APP 81, ¶ 2, 138 P.3d at 839. The claimant stopped working for the employer three months after the date of last exposure. Id. The employer asserted a § 11(B)(5) defense and argued that claimant was injuriously exposed to the trauma by performing manual labor erecting a greenhouse in his subsequent employment of more than ninety (90) days. Id. ¶ 13, 138 P.3d at 840. The claimant responded that he sustained the cumulative trauma injury to his shoulder while working for the first employer, and the subsequent employment only involved light duties and activities that did not aggravate his shoulder. Id. ¶¶ 5, 13, 138 P.3d at 839, 841. The Falling court rejected the employer's § 11(B)(5) defense and clarified:

Id. ¶ 15, 138 P.3d at 841 (emphasis added). The Court of Civil Appeals sustained the trial court's rejection of the employer's § 11(B)(5) defense and determined there was "competent testimony and medical evidence to support the conclusion that Claimant sustained no aggravation of his cumulative trauma shoulder injury in the subsequent employment, and all of Claimant's left shoulder impairment was attributable to the cumulative trauma injury sustained while working for Employer." Id. ¶ 18, 138 P.3d at 842.

¶ 25 The claimant in Neel stopped working for the employer several months after he reported problems with his hands. 2006 OK CIV APP 66, ¶ 2, 136 P.3d at 734. Thereafter, the claimant began building a barbed wire fence for his subsequent employer. Id. ¶ 3, 136 P.3d at 734. The claimant testified that his hands were worse since he left his previous employer and since he had been driving fence posts into the ground and using them continuously during his subsequent employment. Id. Claimant was denied compensability based on § 11(B)(5). Id. ¶ 4, 136 P.3d at 735.

¶ 26 The Court of Civil Appeals adopted the following burden shifting analysis:

Id. ¶ 7, 136 P.3d at 736 (emphasis added).12 The Court of Civil Appeals determined that the claimant in Neel had met his burden of producing evidence that he was exposed to cumulative trauma while employed by the first employer. Id. ¶ 9, 136 P.3d at 736. The first employer met its burden of refuting the claimant's evidence with the claimant's own testimony that his carpal tunnel had gotten worse since he had been building fences for his subsequent employer. Id. ¶ 10, 136 P.3d at 736. The claimant's testimony that he was injuriously exposed to the trauma in his subsequent employment and that his cumulative trauma injury had worsened during his subsequent employment was overwhelming, and the Court of Civil Appeals sustained the panel's order that the subsequent employer was liable for the claimant's benefits. Id.

¶ 27 In the present case, it is undisputed that Claimant has been self-employed for a period of more than ninety (90) days. However, the parties presented conflicting evidence on the issue of whether Claimant was injuriously exposed to the trauma in his subsequent employment. Employer offered Claimant's testimony that he continued to install car windows and train his son in window installation while self-employed. Employer also pointed to a comment in Dr. Hensley's report that if the work with Employer was injurious, then the work in subsequent employment was also injurious. Employer further relied on Dr. Ruffin's deposition testimony that using vibratory tools and pounding glass while self-employed "aggravates" Claimant's condition.

¶ 28 Claimant offered his own testimony that work dropped off after he opened his own shop, that he significantly reduced the number of car windows he installed per day, and that his son started working to ease his work load. Claimant also relied on Dr. Ruffin's deposition testimony. Dr. Ruffin testified that Claimant's symptoms had not changed appreciably since he became self-employed; that continued exposure to the trauma at a reduced pace would not make Claimant's condition worse, but it would not make it better; that if Claimant completely stopped pounding windows and using vibratory tools, his condition would not improve dramatically; and that by "aggravating" he meant maintaining the current condition, not making it worse.

¶ 29 We hold that it was not against the clear weight of the evidence to find Claimant had not suffered injurious exposure to the trauma in his subsequent employment. Claimant's testimony and Dr. Ruffin's testimony support the conclusions that exposure to the trauma while self-employed did not cause or contribute to the resulting disability, that subsequent employment did not make the cumulative trauma injuries worse, and that Claimant's injuries are attributable to cumulative trauma sustained while working for Employer. See Falling, 2006 OK CIV APP 81, ¶¶ 15, 18, 138 P.3d at 841-42; Neel, 2006 OK CIV APP 66, ¶ 9, 136 P.3d at 736.

¶ 30 SUSTAINED.

JOPLIN, V.C.J., and GOREE, J., concur.