Hickory Business Furniture (“defendant-employer”) and its insurance servicing agent, Alexsis, Inc., (collectively, “defendants”) appeal from an opinion and award of the North Carolina Industrial Commission (“the Commission”) finding and concluding that Judy Carolyn Young (“plaintiff’) experienced a substantial change of condition within the meaning of section 97-47 of the North Carolina General Statutes. Having carefully examined defendants’ assignments of error, we affirm the Commission’s opinion and award.
Plaintiff strained her back on 3 March 1992 while picking up a piece of furniture. At the time of the admittedly compensable injury, plaintiff was forty-eight years old and had been employed with defendant-employer for six years. Dr. Robert Hart, a family practitioner who served as defendant-employer’s physician, initially treated plaintiff’s injury and recommended physical therapy for her complaints of mid-back pain. Plaintiff’s symptoms persisted, however, so Dr. Hart referred her to Dr. H. Grey Winfield, III, an orthopedist. Dr. Winfield’s examination found plaintiff to have full range of motion in the lower extremity, to be a bit histrionic in her heel-toe walk, and to exhibit some symptom magnification. Dr. Winfield continued to treat plaintiff through 21 May 1992, after which plaintiff did not return for a follow-up assessment.
On her own, plaintiff sought treatment from Bruce Hilton, D.C., a chiropractor, on 9 November 1992, and on 20 July 1993, he rated her as retaining a 5% permanent partial impairment to her back. At the time of the rating, plaintiff continued to experience pain in her back and right hip and tingling in her right leg. The pain never ceased following plaintiff’s initial treatment by the various doctors and, instead, increased gradually over time. Plaintiff, therefore, returned to Dr. Hilton for chiropractic treatment of a “popping” right hip on 20 August 1994. Dr. Hilton testified that plaintiff’s condition appeared to be the same as when she originally sought his treatment, but the con*53dition had substantially worsened. On 19 October 1994, when plaintiff could no longer physically perform her job, Karen Hightower, plaintiff’s supervisor, terminated plaintiffs employment.
On 19 June 1995, plaintiff began treatment with Dr. Dennis Payne, a rheumatologist with expertise concerning fibromyalgia, a chronic muscular pain syndrome that is associated with a non-restorative sleep pattern. Dr. Payne diagnosed plaintiff as having reactive fibromyalgia resulting from her 3 March 1992 compensable injury.
Plaintiff returned to Dr. Winfield on 2 August 1995 complaining of neck and bilateral arm pain. She also complained of swelling in the hands and back pain that radiated from the neck through the lumbar area and into both legs. Dr. Winfield examined plaintiff and found her to be neurologically intact with a full range of motion for the hips, knees and ankles. Dr. Winfield conducted a series of diagnostic tests, the results of which were normal, and determined that plaintiffs condition was much worse than when he last saw her on 21 May 1992. He concluded, however, that the present symptoms were not causally related to the prior compensable injury.
Plaintiff filed a Form 33, Request for Hearing, on 10 January 1995, alleging a substantial change of condition. The case came on for hearing before Deputy Commissioner Lorrie L. Dollar, who entered an opinion and award on 18 October 1996 finding and concluding that plaintiff had sustained a substantial change of condition within the meaning of section 97-47 of the General Statutes. Defendants appealed to the Full Commission, and on 7 April 1997, the matter was heard by a panel of the Full Commission consisting of Commissioners Thomas J. Bolch, Coy M. Vance, and Dianne C. Sellers. On 2 June 1997, Commissioner Bolch, with Commissioner Vance concurring, filed an opinion and award affirming the deputy commissioner’s decision. Commissioner Sellers dissented, however, finding that plaintiff had failed to meet her burden of proving a substantial change of condition.
Defendants appealed to this Court, and in an opinion filed 21 April 1998, we vacated the opinion and award of the Full Commission and remanded the case for more definite factual findings. On remand, the case was considered by a panel comprised of Commissioners Bolch, Sellers, and Christopher Scott (Commissioner Vance had retired). Commissioner Bolch, with Commissioner Scott concurring, entered an opinion and award on 28 January 1998 finding and con-*54eluding that plaintiff had undergone a substantial change of condition. Commissioner Sellers again dissented on the same grounds. Defendants now appeal.
On appeal from an opinion and award of the Industrial Commission, the reviewing court’s task is to determine (1) whether there is any competent evidence of record to support the Commission’s factual findings and (2) whether those findings, in turn, provide support for the Commission’s conclusions of law. Porter v. Fieldcrest Cannon, Inc., 133 N.C. App. 23, 25, 514 S.E.2d 517, 520 (1999). To that end, the findings by the Commission are binding on the reviewing court if the record contains any competent evidence in their support. Adams v. AVX Corp., 349 N.C. 676, 681, 509 S.E.2d 411, 414 (1998), reh’g denied, 350 N.C. 108, 532 S.E.2d 522 (1999). This is true, even when the record offers evidence that would support findings to the contrary. Id. The Commission’s legal conclusions, however, are subject to this Court’s de novo review. Lewis v. Craven Regional Medical Center, 122 N.C. App. 143, 149, 468 S.E.2d 269, 274 (1996).
 With these principles in mind, we proceed to our discussion of defendants’ arguments. Defendants first contend that the Commission disregarded competent evidence and thereby committed reversible error. In essence, defendants assert that the Commission was required to give some weight to the evidence elicited by the cross-examination of Dr. Payne regarding the etiology of fibromyalgia. Defendants also contend that the Commission failed to give proper weight to the opinion testimony of Dr. Winfield. We must disagree.
As defendants point out, “the Commission may not ‘wholly disregard or ignore competent evidence’ and must consider and evaluate all the evidence” presented by the parties. Jarvis v. Food Lion, Inc., 134 N.C. App. 363, 366-67, 517 S.E.2d 388, 391 (1999) (quoting Pittman v. International Paper Co., 132 N.C. App. 151, 156, 510 S.E.2d 705, 709, disc. review denied, 350 N.C. 310, 534 S.E.2d 596 (1999)). This notwithstanding, the Commission is the sole judge of the credibility of the witnesses and the weight be accorded their testimony. Bailey v. Sears Roebuck & Co., 131 N.C. App. 649, 653, 508 S.E.2d 831, 834 (1998). Furthermore, the Commission “may reject a witness’ testimony entirely if warranted by disbelief of that witness.” Pittman, 132 N.C. App. at 156, 510 S.E.2d at 709.
*55It is apparent from the Commission’s findings of fact that it, indeed, considered the opinion testimony of Dr. Winfield as well as the evidence brought out during the cross-examination of Dr. Payne. In Finding of Fact #5, the Commission notes that Dr. Winfield was of the opinion that plaintiffs current complaints were “not causally related to the prior compensable injury.” The Commission states, however, that it “[gave] no weight to this opinion inasmuch as Dr. Winfield has no expertise concerning fibromyalgia.” Regarding Dr. Payne’s testimony on cross-examination, the Commission states the following in Finding of Fact #18:
Defendants’ counsel’s cross-examination of Dr. Payne did not result in a change of his opinion that plaintiff had disabling fibromyalgia caused or aggravated by her March 3, 1992, injury by accident. Nothing elicited by such cross examination causes the Full Commission to modify its finding of facts.
Since the Commission was well within its authority to reject what it deemed to be unreliable evidence, defendants’ argument is without merit.
 Defendants next argue that the Commission erred in finding and concluding that plaintiff’s fibromyalgia was causally related to her 3 March 1992 injury. Defendants’ chief contention is that because the etiology of fibromyalgia cannot be scientifically or objectively determined, Dr. Payne’s opinion as to the cause of plaintiff’s condition is no more than speculation and conjecture. Again, we disagree.
The Industrial Commission is vested with full authority to find the essential facts in a workers’ compensation case, Bailey, 131 N.C. App. at 653, 508 S.E.2d at 834, and it is the responsibility of the Commission, not the reviewing court, to weigh the evidence of causation and to assess its credibility, id. at 653, 508 S.E.2d at 835. Therefore, this Court can do no more than examine the record to determine whether any competent evidence exists to support the Commission’s findings as to causation, and we are not at liberty “to weigh the evidence and then decide the issue on the basis of its weight.” Porter, 133 N.C. App. at 26, 514 S.E.2d at 520. “[W]hen conflicting evidence is presented, ‘the Commission’s finding of causal connection between the accident and the disability is conclusive.’ ” Bailey, 131 N.C. App. at 655, 508 S.E.2d at 835 (quoting Anderson v. Lincoln Construction Co., 265 N.C. 431, 434, 144 S.E.2d 272, 275 (1965)).
*56Defendants maintain that Dr. Payne’s testimony regarding the cause of plaintiff’s condition should have been excluded as unreliable. Defendants take the position that the lack of definitive scientific methodology verifying the cause and effect relationship between plaintiff’s compensable injury and her subsequent fibromyalgia rendered Dr. Payne’s opinion incompetent and inadmissible. However, Dr. Payne, as an expert in the field of rheumatology and the treatment of fibromyalgia, was in a better position than the fact-finding body to draw a conclusion from the relevant circumstances as to what brought on plaintiff’s current condition. The Commission was then free to receive this testimony and adopt Dr. Payne’s conclusion as fact. Thus, contrary to defendants’ assertion, we conclude that plaintiff has met her burden of establishing a causal connection between the fibromyalgia and her 3 March 1992 injury in terms of “reasonable medical probability.”
Dr. Payne testified that “[f]ibromyalgia is a clinical diagnosis,” which means that it is diagnosed “based on history and examination rather than doing any type of testing or x-ray studies.” He stated that fibromyalgia “produces soft tissue pain and tenderness ... in very characteristic locations in a person’s body.” Dr. Payne further stated that “[plaintiff] had the tender points and they were in the characteristic locations that we see in this problem.” He indicated that “[plaintiff] fulfill[ed] the American College of Rheumatology criteria for fibromyalgia.” According to Dr. Payne, “reactive fibromyalgia” is related, in time, to a particular event and could be caused or aggravated by trauma. While Dr. Payne conceded that fibromyalgia is controversial “because there’s difficulty in objectively studying [the condition],” it was his opinion, to a reasonable degree of medical certainty, that plaintiff’s compensable “injury could have or would have aggravated or caused the fibromyalgia.” Dr. Payne noted further that plaintiff’s history did not reveal any causative factor, other than the work-related injury, for the onset of fibromyalgia.
In light of this testimony, we hold that Dr. Payne’s opinion regarding the etiology of plaintiff’s current condition is more than mere speculation and, thus, was sufficient to support the Commission’s finding that “[plaintiff’s] reactive fibromyalgia was caused or substantially aggravated by her original injury by accident.” See Hedrick v. PPG Industries, 126 N.C. App. 354, 484 S.E.2d 856, disc. review denied, 346 N.C. 546, 488 S.E.2d 801 (1997) (holding that although cause of dystonia unknown, expert’s opinion regarding causation, based on temporal relationship between plaintiff’s work-related *57injury and onset of condition, was sufficient to support Commission s finding that dystonia was caused by compensable injury); Keel v. H & V Inc., 107 N.C. App. 536, 421 S.E.2d 362 (1992) (stating that causal connection may be established by circumstantial evidence and that absolute medical certainty not required). Defendants’ argument, then, fails.
 Lastly, defendants assert that the evidence does not support the Commission’s conclusion that plaintiff experienced a substantial change of condition, because Dr. Hilton testified that he would have given her the same disability rating in 1995 that he gave her in 1993, i.e., 5% permanent partial impairment to the back. We are not persuaded.
Under section 97-47 of our General Statutes, a “change of condition” refers to “ ‘a substantial change, after a final award of compensation, of physical capacity to earn and, in some cases, of earnings.’ ” East v. Baby Diaper Services, Inc., 119 N.C. App. 147, 151, 457 S.E.2d 737, 740 (1995) (quoting Pratt v. Upholstery Co., 252 N.C. 716, 722, 115 S.E.2d 27, 34 (1960)). Whether a change of condition has occurred is a factual question, and whether the facts as found constitute a change of condition is a legal question. Id.
Defendants cite no authority for the proposition that an injured employee’s disability rating must change in order to conclude that she has suffered a substantial change of condition under section 97-47. Moreover, we note that “[i]n determining if a change of condition has occurred entitling an employee to additional compensation under G.S. 97-47 the primary factor is a change in condition affecting the employee’s physical capacity to earn wages[.]” Lucas v. Bunn Manuf. Co., 90 N.C. App. 401, 404, 368 S.E.2d 386, 388 (1988). The record contains ample evidence tending to show that plaintiff’s physical condition changed so as to impact her wage-earning capacity. Dr. Winfield testified that when he examined plaintiff on 2 August 1995, her condition was much worse than when he last saw her on 21 May 1992. Dr. Hilton similarly testified that plaintiff’s condition had substantially worsened when she returned to him for treatment on 20 August 1994. Furthermore, plaintiff presented evidence that she was terminated from her position with defendant-employer on 19 October 1994, because she was no longer physically able to perform her job. We, therefore, hold that the Commission did not err in concluding that plaintiff underwent a substantial change of condition within the meaning of section 97-47. Accordingly, defendants’ argument is overruled.
*58In light of the foregoing analysis, we affirm the opinion and award of the Industrial Commission.
Judge MARTIN concurs.
Judge HORTON dissents with a separate opinion.