
895 P.2d 719 (1995)
FARM FRESH, INC., Petitioner,
v.
Charles BUCEK and the Workers' Compensation Court, Respondent.
No. 82854.
Supreme Court of Oklahoma.
May 9, 1995.
Charles S. Plumb, Benjamin J. Chapman, Doerner, Stuart, Saunders, Daniel, Anderson & Biolchini, Tulsa, for petitioner.
Art G. Mata, Mata, & Mata, Lawton, for respondent.
*720 OPALA, Justice.
The dispositive issues presented on certiorari are: [1] Does the 85 O.S. 1991 § 17(D)[1] requirement  that a trial tribunal's deviation of more than 10% from the impairment rating by an independent court-appointed physician be specifically identified  apply to evaluation of permanent total disability? and if not [2] Is the trial tribunal's award of permanent total disability supported by competent evidence? We answer the first question in the negative and the second in the affirmative.

I

THE ANATOMY OF LITIGATION
The claimant, Charles Bucek [claimant or Bucek], was employed as a maintenance engineer for Farm Fresh Bakery [employer]. While repairing a bun oven on October 1, *721 1989, he slipped on an oil-slick floor, sustaining injuries to his neck, back and left shoulder. The trial tribunal ordered the claimant's examination by an independent medical expert [Dr. H. or IME].
At the August 24, 1993 hearing several medical reports and records were admitted. The claimant's rating physician, Dr. E., concluded that Bucek had sustained 85% permanent partial impairment to the whole person and as a result was permanently totally disabled. The employer's rating physician, Dr. C., stated that the claimant had sustained 16% permanent partial impairment to the body. Dr. H., the court-appointed physician, who had been the claimant's treating physician, opined that Bucek had sustained 11% permanent partial impairment to the whole person. According to Dr. H., the claimant could return to work.
The trial tribunal entered an award for permanent total disability,[2] which gave no explanation for its 89% in impairment deviation from the rating in the IME report. On appeal to a three-judge review panel, the employer argued that, in light of the IME's 11% permanent partial impairment assessment, the trial tribunal's determination of the claimant's permanent total disability had no support in the record or in compensation law. By its December 21, 1993 decision the review panel adopted the trial tribunal's award of permanent total disability. This proceeding for corrective relief, brought by the employer, followed.
The Court of Appeals sustained the panel's decision, holding that (a) the question whether claimant is permanently totally disabled is one of fact to be reviewed by the familiar standard of competent medical proof, and (b) the § 17(D)[3] requirement  that a trial tribunal's deviation of more than 10% from the IME impairment rating be specifically identified  applies only to evaluations of permanent impairment and not to a permanent total disability rating.[4]
Although we reach the same result as the Court of Appeals, we vacate that court's opinion to provide a more extensive guidance for the distinction between impairment and disability in the post-1977 benefits regime.

II

THE "IMPAIRMENT" AND "DISABILITY" DISTINCTION IN THE 1977 WORKERS' COMPENSATION ACT
The employer urges that the trial judge impermissibly deviated more than 10% from IME's impairment rating because he failed to provide the explanation required by § 17(D) of the compensation law.[5] This issue calls for an analysis of the conceptual distinction between disability and impairment embodied in the 1977 Workers' Compensation Act [1977 Act].[6] When examining the impact of this legislation, it is helpful first to explore Oklahoma's pre-1977 benefits regime.

The Pre-1977 Disability-Based Compensation Scheme
When first enacted in 1915, Oklahoma's regime for delivery of benefits to an injured worker was designed to restore lost earnings for compensable harm from "hazardous employment".[7] This institutional design established four categories of disability-based benefits *722 (permanent total, temporary total, permanent partial and temporary partial).[8] The key term "disability" was not defined by statute. The court eventually came to measure it by a worker's capacity to perform "ordinary manual or mechanical labor".[9] An injury to a specific, scheduled member of the body (a classified disability) was measured by the number of weeks in the member schedule,[10] while one to an "unclassified part of the body" fell under the "other cases" clause of § 22[11] and was compensated on the basis of percentage disability to the body as a whole.[12]

The 1977 Act's Disability-Based and Impairment-Related Benefits Regime
The 1977 Act made two significant changes in the compensation law. It extended coverage to nearly all Oklahoma employees (not just to those in "hazardous employment") and introduced a mixed impairment-related and disability-based benefits regime. The terms disability and impairment were given distinct meanings.
Disability is designed to measure an employee's capacity for work, i.e., the degree to which an injury affects a person's ability to perform any task for which the worker is reasonably suited by training, education and experience.[13] The purpose of disability-related compensation in the 1977 Act is to replace the incapacitated worker's lost earnings[14] for injury to the limbs based on the number of weeks assigned as a maximum for each limb. The Act left intact this (pre-1977) wage-replacement concept of disability but confined its application solely to (1) temporary (temporary total and temporary partial) and (2) permanent total benefits.[15] Permanent total disability is defined as "[i]ncapacity because of accidental injury or occupational disease to earn any wages in any employment for which the employee is or becomes physically suited and reasonably fitted by education, training or experience."[16] In *723 short, a permanently and totally disabled worker within the meaning of the Act is one eligible for wage replacement because of lack of capacity to earn any wages.
Impairment, on the other hand, is a medical condition; it refers to the effect of the injury upon a person's ability to perform basic life functions.[17] The term permanent impairment is defined as "any anatomical or functional abnormality or loss after reasonable medical treatment has been achieved, which abnormality or loss the physician considers to be capable of being evaluated at the time the rating is made."[18]Permanent partial disability means "permanent disability" and is the "same as permanent impairment."[19] This definition not only signifies a complete departure from the old theory of ordinary manual or mechanical labor, but also introduces a new and more specific concept for evaluating permanent partial disability by placing it on a footing absolutely equal with permanent impairment, i.e. loss of bodily function.
The American Medical Association Guides to the Evaluation of Permanent Impairment [AMA Guides][20] provides helpful insight into the impairment-disability dichotomy. An impairment is viewed as a "medical matter", whereas disability is deemed to "arise out of the interaction between impairment and external demands."[21] As used in the AMA Guides, (a) impairment means "an alteration of an individual's health status that is assessed by medical means," and (b) disability, "which is assessed by nonmedical means, means an alteration of an individual's capacity to meet personal, social, or occupational demands, or to meet statutory or regulatory requirements."[22]With the sole exception of scheduled member losses, total or partial, the AMA Guides must be used for rating permanent impairment.[23] In short, permanent partial disability, as distinguished from other payout classes, contemplates recompense for lost physical fitness, though the amount paid the worker must be measured by a percentage *724 of wages he (or she) would have earned but for the covered injury.[24]
The terms of § 17(D)[25] require that a trial tribunal specifically identify the reason for its award's deviation of more than 10% from the impairment rating by an independent court-appointed physician. Section 17(D), construed together with §§ 3(11)[26] and (13)[27]  the latter two of which define the terms permanent impairment and permanent partial disability  indicates that it is intended to deal with medical permanent partial impairment ratings.
The issue of permanent total disability turns on the evaluation of the worker's present capacity "to earn any wages in any employment for which he is presently suited or fitted by education, training or experience."[28] The determination of a claimant's disability-based benefits presents a fact question for the trial tribunal.[29] Its finding in this case declared Bucek to be totally and permanently disabled. Because § 17(D) has no application to disability-related benefits, the trial tribunal neither grounded its award in the AMA Guides nor was it statutorily required to explain why that award deviated (by 89%) from the IME's impairment rating.[30]

III

THE TRIAL TRIBUNAL'S PERMANENT TOTAL DISABILITY AWARD IS SUPPORTED BY COMPETENT EVIDENCE
While the panel's review of the trial tribunal's findings is governed by a clear-weight-of-the-evidence test,[31] this court, when examining that tribunal's factual resolutions, applies the any-competent-evidence standard.[32] If supported by competent evidence, the panel's findings may not be disturbed on review.[33]

A.
The employer's expert evidence, consisting mostly of medical reports and records, was admitted without objection. Its proof included reports from (a) Dr. C., the employer's rating physician, and (b) Dr. H., the court-appointed physician, who also treated the claimant. Dr. H., who gave him an 11% permanent partial impairment rating (to the whole person,) stated that the claimant could return to work but recommended that he receive some vocational counselling. According to Dr. C.'s report, the claimant had sustained 16% permanent partial impairment.
The claimant's proof consists of two letter-reports by his medical expert, Dr. E., and of some other medical records. In his reports *725 (one eight-page and another one-page analyses), Dr. E. opines that the claimant is permanently totally disabled. The longer report gave the claimant an 85% permanent partial impairment rating and attributed it to the combined injury of his neck, back, spinal cord, and left shoulder. According to Dr. E.'s shorter report, he did not think the claimant "is going to be able to be retrained." In the next sentence this physician opines that because the claimant is "well motivated." he "may possibly be re-trained." This report was admitted over the employer's challenge to its probative value based on a seeming inconsistency in the quoted language.
Our review of the record reveals that the award of permanent total disability rests on competent evidence. The claimant's medical proof fully explains the reasons for Dr. E.'s opinion. His comprehensive (eight-page) report contains (a) a relevant history of the claimant's injuries, complaints and medical treatment, (b) a description of the examination, tests, and medical records reviewed, as well as (c) an evaluation of the extent of his impairment. This report clearly informs that were the claimant returned to work, he could not perform if he were required to stand for more than an hour or to sit for more than 20 minutes. According to Dr. E.'s explanation, the claimant cannot do repetitive work with his left arm or any work with his left arm above his waist. This is so because the claimant cannot do any work if he has to sit with his neck in one position, such as he would occupy when reading or looking at a monitor. The claimant, who has but a high school education, must have the ability to move and lay down. He had previously worked as a maintenance man. As a result of his injuries (serve pain in his neck and left shoulder, coupled with pain and weakness in his left arm and leg), Dr. E. finally concludes in his "bottom line" that it is doubtful Bucek could return to any type of gainful employment for which he is or could become reasonably suited by education, training or experience.

B.
The employer also argues that the claimant has the ability "to earn any wages in any employment" within the meaning of § 3(12).[34] In support of its position the employer directs us to the claimant's testimony that (a) he has been employed twice since his accidental injury for a period of about six weeks; (b) he is an Army veteran with a GED (general high school equivalent diploma) and some microscopic college credits; (c) he is able to drive and was employed as a driver after his injuries; and (d) he has custody of, and cares for, his 4- and 5-year old grand children.
Although ordinarily the employer has the burden of establishing facts that challenge the claimant's entitlement to benefits under the workers' compensation law, when, as here, the record shows the worker has been continuously employed since the initial injury, the onus shifts to the worker to produce expert evidence that will overcome the contrary proof from the employer.[35] The claimant met the law's requirement.
According to the record, the claimant attempted to work after his injury, but was unable to keep a job because of intense pain that prevented him from meeting his employer's standards. His testimony is supported by competent medical evidence based on Dr. E.'s clinical findings. Bucek has been a manual laborer for some 30 years, working in the oil field as a roughneck and driller. According to him, he has relied upon manual labor for his livelihood because he has neither formal education nor training. He acquired his GED while in the Army, where he also received his only two college credits (the latter some 27 years ago). The claimant explained that while his grandchildren live with him, he is not their primary care giver while they remain in his home. He does not drive them to and from school. The grandchildren are away from the home during the day from *726 9:00 a.m. until his wife picks them up at 5:00 p.m.
We hold that, on this record, there is competent medical evidence to support the trial tribunal's award for permanent total disability.

CONCLUSION
Oklahoma's current benefits regime gives a distinct legal meaning to the terms impairment and disability. A disability-related award, which is designed to replace a worker's lost wages while he (or she) is unable to work, is assessed mainly upon nonmedical means  i.e., the claimant's training, education and experience. An impairment-based award must rest solely on the claimant's health condition and is measured entirely by medical standards for measuring the loss of bodily function. The statutory requirement in § 17(D)  that any deviation between an award's and a court-appointed physician's impairment rating be specifically explained  addresses itself solely to impairment-based awards. Claimant's medical evidence competently supports the award of permanent total disability by overcoming the proof that he may have retained a sufficient residual capacity for work in gainful employment.
ON CERTIORARI PREVIOUSLY GRANTED, THE COURT OF APPEALS' OPINION IS VACATED AND THE REVIEW PANEL'S ORDER IS SUSTAINED.
ALMA WILSON, C.J., KAUGER, V.C.J., and LAVENDER, SIMMS, HARGRAVE, OPALA and WATT, JJ., concur;
HODGES and SUMMERS, JJ., dissent.
NOTES
[1]  For the pertinent terms of 85 O.S. 1991 § 17(D), see infra note 5.
[2]  The parties stipulated at the hearing to the rates of $208.01 for temporary total and permanent total disability and $173.00 for permanent partial disability.
[3]  For the pertinent terms of 85 O.S. 1991 § 17(D), see infra note 5.
[4]  The Court of Appeals relied on Bi-Lo Food Warehouse v. McCause, Okl.App., 836 P.2d 689 (1992), which holds that § 17(D) applies only to awards of permanent impairment and not to temporary total disability.
[5]  The terms of 85 O.S. 1991 § 17(D) (the version in effect at the time of the hearing) are:

"D. The impairment rating determined by the third physician may be followed by the Court. If the Court deviates from the third physician's impairment rating by more than ten percent (10%), the Court shall specifically identify the basis for such deviation in its order."
[6]  85 O.S.Supp. 1977 §§ 1 et seq.
[7]  See Nelson v. Rialto Mining Co., 194 Okl. 628, 154 P.2d 87, 89 (1944); United States Casualty Co. v. Steiger, 179 Okl. 407, 66 P.2d 55, 57 (1937).
[8]  For the pre-1977 compensation regime, see 85 O.S. 1971 § 22. [1] Temporary Total Disability is the "healing period or that period of time following accidental injury, when an employee is totally incapacitated for work due to illness resulting from injury." Oklahoma Natural Gas Co. v. Davis, 181 Okl. 530, 75 P.2d 435, 436 (1938). The benefits payable were a percentage of the state's average weekly wage to be paid during the continuance of the disability but not to exceed a maximum number of weeks. [2] Temporary Partial Disability pertains to a healing period during which the employee has some capacity to work. Orman v. Capital Steel and Iron Co., Okl., 289 P.2d 375, 377 (1955). [3] Permanent Total Disability constitutes a lack of ability to perform substantially in gainful employment without injury to health or serious discomfort. McClure v. Special Indemnity Fund, Okl., 475 P.2d 811, 812 (1970); Dierks Lumber & Coal Co. v. Lindley, 182 Okl. 185, 77 P.2d 44, 46 (1938). [4] Permanent Partial Disability is based on a percentage of loss in the capacity of the body as a whole to perform labor. Mayberry v. Walker's Masonry, Okl., 542 P.2d 510, 514 (1975), J.E. Trigg Drilling Co. v. Daniels, 193 Okl. 644, 145 P.2d 944 (1943). An earlier (1941) amendment eliminated the need to establish loss of earning power in order to receive compensation for permanent partial disability. Service Pipe Line Company v. Cargill, Okl., 289 P.2d 961, 962-963 (1955); Folsom Auto Supply v. Bristow, Okl., 275 P.2d 706, 710 (1954). See also Amerada Petroleum Corporation v. Lovelace, 184 Okl. 140, 85 P.2d 407 (1938) (syllabus ¶ 1), where the court held that a claimant is entitled to compensation for permanent partial disability "without regard to the effect thereof upon his carning capacity."
[9]  See J.E. Trigg Drilling Co., supra note 8, 145 P.2d at 946, where the court held that "[d]isabilities within the meaning of the act refer to lack of ability to do ordinary manual or mechanical work and labor... ." (Emphasis added.)
[10]  See 85 O.S. 1971 § 22; Stoldt Builders, Inc. v. Thomas, Okl., 393 P.2d 875, 877 (1964).
[11]  See 85 O.S. 1971 § 22.
[12]  Stoldt, supra note 10 at 877.
[13]  See 85 O.S.Supp. 1988 § 3(12) (quoted in the text at infra note 16); TWA v. McKinley, Okl., 749 P.2d 108, 110 (1988); Eslinger v. Cole Grain Co., Okl.App., 655 P.2d 164, 165-166 (1982) (overruled in part on other grounds by TWA, supra at 109).
[14]  Nelson, supra note 7, 154 P.2d at 89; Steiger, supra note 7, 66 P.2d at 57; see Sturm, The Workers' Compensation Act of 1977, 3 OKL.CITY UNIV.L.R. 1, 12-14 (1978).
[15]  See 85 O.S.Supp. 1986 § 22.
[16]  The terms of 85 O.S.Supp. 1988 § 3(12) provided:

"(12) `Permanent total disability' means incapacity because of accidental injury or occupational disease to earn any wages in any employment for which the employee is or becomes physically suited and reasonably fitted by education, training or experience; loss of both hands, or both feet, or both legs, or both eyes, or any two thereof, shall constitute permanent total disability." (Emphasis added.)
The 1990, 1992, 1993 and 1994 amendments to § 3 have no effect on this review proceeding.
[17]  Sturm, supra note 14 at 13-14.
[18]  The terms of 85 O.S.Supp. 1988 § 3(11) provided:

"(11) `Permanent impairment' means any anatomical or functional abnormality or loss after reasonable medical treatment has been achieved, which abnormality or loss the physician considers to be capable of being evaluated at the time the rating is made. Except as otherwise provided herein, any examining physician shall only evaluate impairment in accordance with the latest `Guides to the Evaluation of Permanent Impairment' adopted and published by the American Medical Association The examining physician shall not deviate from said guides except as may be specifically provided for in the guides. These officially adopted guides shall be the exclusive basis for testimony and conclusions with regard to permanent impairment with the exception of paragraph 3 of Section 22 of this title, relating to scheduled member loss; and impairment, including pain or loss of strength, may be awarded with respect to those injuries or areas of the body not specifically covered by said guides." (Emphasis added.)
The 1990, 1992, 1993 and 1994 amendments to § 3 have no effect on this review proceeding.
[19]  The terms of 85 O.S.Supp. 1988 § 3(13) are:

"(13) `Permanent partial disability' means permanent disability which is less than total and shall be equal to or the same as permanent impairment." (Emphasis added.)
The 1990, 1992, 1993 and 1994 amendments to § 3 have no effect on this review proceeding.
[20]  AMA Guides, 3d Ed. (1988).
[21]  AMA Guides, supra note 20, Ch. 1, ¶ 1.1.
[22]  AMA Guides, supra note 20, Ch. 1, ¶ 1.1 (emphasis in original). The AMA Guides explains that an impaired individual is not necessarily disabled. Impairment gives rise to disability only when the medical condition limits the individual's capacity to meet demands that pertain to nonmedical fields and activities. On the other hand if the individual is able to meet a particular set of demands, the individual is not disabled with respect to those demands, even though a medical evaluation may reveal impairment. Id., supra note 20, Ch. 1, ¶ 1.1.
[23]  85 O.S.Supp. 1988 § 3(11), supra note 18; Rule 23, Workers' Compensation Court Rules, 85 O.S. 1991, Ch. 4, App.; B.F. Goodrich v. Hilton, Okl., 634 P.2d 1308, 1310 (1981).
[24]  85 O.S.Supp. 1988 § 22(3).
[25]  For the pertinent terms of 85 O.S. 1991 § 17(D), see supra note 5.
[26]  For the terms of 85 O.S.Supp. 1988 § 3(13), see supra note 18.
[27]  For the terms of 85 O.S.Supp. 1988 § 3(13), see supra note 19.
[28]  See 85 O.S.Supp. 1988 § 3(11), supra note 18.
[29]  Green Country Restaurant v. Carmen, Okl., 579 P.2d 1281 (1978).
[30]  The court's analysis in Crocker v. Crocker, Okl., 824 P.2d 1117 (1991), is neither relevant nor helpful in this cause. Crocker deals solely with the characteristics of various awards in terms of their divisibility as a spousal asset. The teachings of Roberts v. Matrix Services, Inc., Okl., 863 P.2d 1242 (1993), target overcompensation which results from an award that rests on two inconsistent components of the benefits regime. It is neither argued in this case, nor do we find, that the award is based on an impermissible intermixture of the two discrete statutory compensation schemes.
[31]  85 O.S.Supp. 1993 § 3.6A; Parks v. Norman Mun. Hosp., Okl., 684 P.2d 548, 549 (1984).
[32]  Owings v. Pool Well Service, Okl., 843 P.2d 380, 382-383 (1992); Lacy v. Schlumberger Well Service, Okl., 839 P.2d 157, 160 (1992); York v. Burgess-Norton Mfg. Co., Okl., 803 P.2d 697, 699 (1990); Parks, supra note 31 at 549; Graves v. Safeway Stores, Inc., Okl., 653 P.2d 1236, 1238 (1982); Standish Pipe Line Co. v. Kirkland, 188 Okl. 248, 107 P.2d 1024, 1025 (1940); Barnes v. Indian Territory Illuminating Co., 170 Okl. 520, 41 P.2d 633, 635 (1935).
[33]  Parks, supra note 31 at 549; Carpenter v. Douglas Aircraft Company, Okl., 420 P.2d 911, 912 (syllabus ¶ 2) (1966); Leffler v. McPherson Brothers Transport, Okl., 396 P.2d 491, 493 (1964).
[34]  For the pertinent terms of 85 O.S.Supp. 1988 § 3(12), see supra note 16.
[35]  Special Indemnity Fund v. Stockton, Okl., 653 P.2d 194, 198 (1982) (overruled in part on other grounds by Special Indem. Fund v. Choate, Okl., 847 P.2d 796, 810 n. 31 (1993)).
