On judicial review the district court affirmed the decision of the industrial commissioner. The industrial commissioner had adopted the deputy commissioner’s arbitration decision as final agency action. The deputy commissioner had awarded scheduled temporary and permanent disability benefits to the employee arising from a cumulative bilateral upper extremities injury. On appeal we transferred the case to the court of appeals. After the court of appeals affirmed the decision of the district court, we granted the employee’s application for further review. Upon review we find it was error to exclude lay witness testimony as a sanction for failure to supplement interrogatories under the circumstances of this case. We vacate the decision of the court of appeals, reverse the district court decision, and remand to the industrial commissioner for reconsideration.
*419I. Background.
In June 1981, the petitioner, Joyce Miller, began to work for Lauridsen Foods, Inc. as a meat trimmer. In August 1985 she was treated for right wrist and forearm tendonitis. Miller was told by her doctor that she was developing bilateral carpal tunnel syndrome. In September 1986 a medical examination indicated Miller had tendonitis in both forearms requiring her to be off work several days. In the summer of 1987, three surgeries were performed on her for carpal tunnel syndrome. Miller returned to work in the fall of 1987 with restrictions and in February 1988 the restrictions were removed. She was hospitalized for depression in June of 1988. After her release from the hospital, she did not return to work for Lauridsen Foods.
Miller filed three separate workers’ compensation claims against her employer and its insurance carriers in June of 1988. In case No. 878992, she claimed the working conditions at Lauridsen Foods were so difficult, given her physical condition, that on June 14,1988 a mental condition was brought on. In the two other cases Miller claimed that in 1985 or 1986 she suffered cumulative trauma, overuse syndrome, causing injury to her upper extremities, shoulder and neck.
In case No. 878992 Lauridsen Foods and carrier Hartford Insurance Company promptly filed interrogatories requesting the names of persons who had knowledge of Miller’s alleged physical or mental condition and the names of persons she expected to call at trial. Miller’s response, filed in 1988, identified her husband David and professionals of a mental health center. The response did not identify Julie Larson, Jerry Larson, or Milan Harris as persons with knowledge or who Miller intended to call at trial. No comparable interrogatories were submitted by Lauridsen Foods and the carrier Employers Mutual Companies as to the other two cases.
In April 1989 the deputy commissioner ordered Miller’s three cases be consolidated. Case No. 878992 was dismissed by Miller in 1990. Later, when the deputy commissioner entered a pretrial order requiring the parties to specify all witnesses they expected to testify at trial, Miller’s witness list included her husband, Julie Larson, Jerry Larson, and Milan Harris.
Hearing on Miller’s claims was conducted on March 13,1991 by the deputy commissioner. Immediately before the commencement of the hearing, Lauridsen Foods and its carriers delivered to Miller’s counsel a motion to exclude the lay witnesses as a sanction because Miller had failed to supplement her interrogatory response in case No. 878992. In resistance, Miller argued she had no duty to supplement interrogatories in a case that had been dismissed, that the lay witnesses had been listed in the response to the deputy commissioner’s pretrial order, and that under the rules of civil procedure the consolidation did not result in a merger of the cases. The deputy commissioner adopted a consolidation theory of merger and granted the motion which excluded the lay witnesses from testifying. On appeal, the arbitration decision of the deputy commissioner was adopted by the industrial commissioner after making certain modifications of the decision sought by the employer and its carriers.
On judicial review, the district court concluded that Lauridsen Foods and its carriers had a right to rely on the answers to interrogatories because the three claims had been consolidated. Therefore, the discretionary ruling of the deputy commissioner was not an abuse of discretion. The court of appeals agreed the sanction was appropriate.
II. Consolidation of Claims.
Generally, the rules of civil procedure govern contested case proceedings before the industrial commissioner unless the provisions are in conflict with department rules of the provisions of the Iowa Code. 343 Iowa Admin.Code 4.35 (1991). The industrial commissioner on motion or at pretrial may consolidate separate claims involving common questions of fact and law. Iowa R.Civ.P. 185; 343 Iowa Admin.Code 4.9(7), 4.20(8).
Iowa’s rule on consolidation is modeled after federal rule 42. We agree with the interpretation of the rule as expressed in *420Cole v. Schenley Industries, Inc., 563 F.2d 35, 38 (2d Cir.1977). As stated therein:
Consolidation under Rule 42(a), Fed.R.Civ. P., is a procedural device designed to promote judicial economy, and consolidation cannot effect a merger of the actions or the defenses of the separate parties. It does not change the rights of the parties in separate suits.
Id. (citations omitted). Although cases may be consolidated for trial, the eases generally preserve their separate identity.
III. Discovery Sanctions.
Discovery procedures applied in civil cases are available in contested cases before an agency. Iowa Code § 17A.13(1) (1991). Interrogatories may be submitted by a party and the failure to answer interrogatories is subject to sanctions. Iowa R.Civ.P. 122, 126, 134. Here the deputy commissioner’s authority to impose sanctions for failure to comply with discovery in case No. 878992 was removed by the dismissal of that action. An interrogatory related to an issue raised in one of the consolidated cases may be irrelevant to issues raised in the other ease or cases. Miller had the right to dismiss the claim and avoid sanctions that might otherwise have been imposed. See Venard v. Winter, 524 N.W.2d 163 (Iowa 1994) (plaintiff may voluntarily dismiss action and refile an identical action to avoid the consequences of failing to identify expert witnesses before statutory deadline). It was error for the court to exclude the lay witnesses as a sanction for failure to comply with discovery.
IV. Harmless Error.
If it was error to exclude nonmedical witness testimony, counsel for Lauridsen Foods and its carriers urge the error was harmless. To determine if this error is harmless, we consider if the exclusion of lay testimony is prejudicial to Miller. This requires that we consider the nature of her claims.
Miller claims her injuries occurred gradually and cumulatively from a series of traumas and resulting treatments in 1985 through 1988. She alleges her upper extremities, shoulder, and neck were injured causing a permanent partial disability of the body as a whole. The claimant has the burden to establish “the disability proximately caused by the injury.” Freeman v. Luppes Transp. Co., Inc., 227 N.W.2d 143, 148 (Iowa 1975); Poole v. Hallett Constr. Co., 261 Iowa 481, 484, 154 N.W.2d 716, 718 (1967) (Burden of claimant to show “that the condition complained of was causally connected to the injury received in the course of employment.”).
Iowa has adopted the cumulative injury rule. McKeever Custom Cabinets v. Smith, 379 N.W.2d 368, 374 (Iowa 1985). This rule may apply when the disability develops over a period of time. Id. at 373. For workers’ compensation purposes a cause is proximate if it is a cause; it need not be the only cause. Blacksmith v. All-American, Inc., 290 N.W.2d 348, 354 (Iowa 1980). When there has been a compensable injury and the claimant’s injury-related disability is increased or prolonged by a trauma-connected neurosis, all disability, including the effects of such nervous disorder, is compensa-ble. Gosek v. Garmer & Stiles Co., 158 N.W.2d 731, 733 (Iowa 1968).
Scheduled disability is evaluated on a functional basis; unscheduled disability is determined industrially. Simbro v. Delong’s Sportswear, 332 N.W.2d 886, 889 (Iowa 1983). Industrial disability goes beyond body impairment and measures the extent to which the injury impairs the employee’s earning capacity. Second Injury Fund of Iowa v. Shank, 516 N.W.2d 808, 815 (Iowa 1994). Functional disability is arrived at by determining the impairment of the employee’s bodily function and is limited to the loss of the physiological capacity of the body or body part. Id. If an employee suffers both an injury to a scheduled member and also to part of the body not included in the schedule, then the resulting injury is compensated on the basis of an unscheduled injury. Honeywell v. Allen Drilling Co., 506 N.W.2d 434, 436 (Iowa 1993); Mortimer v. Fruehauf Corp., 502 N.W.2d 12, 16 (Iowa 1993).
The employer and carriers argue there was no prejudice in excluding three lay witnesses because “the record was replete with opinions of various experts regarding Miller’s limitations and alternative impairment rat-*421tags.” Based on “the greater weight of the medical evidence” the deputy commissioner’s findings, which were adopted by the commissioner, concluded Miller had incurred simultaneous bilateral work-related carpal tunnel syndromes requiring surgeries on both wrists and a right cubital and ulnar tunnel release in 1987. “Based on the great weight of medical evidence” the commissioner found Miller had three percent permanent partial impairment to her upper extremities, a scheduled disability that entitled her to twenty weeks of permanent partial disability benefits. The commissioner also found “the greater weight of the medical evidence” shows no objective findings to indicate a work-related injury to Miller’s neck and shoulder, and that the medical evidence was tainted by incorrect or inadequate history. Thus, it is argued, any testimony from non-medical witnesses of claimant’s limitations is irrelevant and immaterial. We do not agree.
It is a fundamental requirement that the commissioner consider all evidence, both medical and nonmedical. Lay witness testimony is both relevant and material upon the cause and extent of injury. Giere v. Aase Haugen Homes, Inc., 259 Iowa 1065, 1072, 146 N.W.2d 911, 915-16 (1966). Expert medical testimony may be “buttressed by supportive lay testimony.” McKeever, 379 N.W.2d at 374. We have considered lay witness testimony in determining an employee’s disability and functional impairment. Lauhoff Grain Co. v. McIntosh, 395 N.W.2d 834, 840 (Iowa 1986).
There was medical testimony that Miller suffered a twenty-six percent impairment of her left arm, a thirty-seven percent impairment to her right arm and a three percent impairment of her spine. Other medical testimony found some physiological cause of her neck and shoulder pain. Lay testimony could buttress the medical testimony and would be relevant and material in determining the cause and extent of Miller’s injuries and condition. It was error for the commissioner to exclude lay witnesses as a sanction and such error was not harmless.
V. Disposition.
We reverse the commissioner’s decision and return this case to the commissioner for the purpose of receiving additional evidence by the designated lay witnesses. The commissioner shall then reconsider and weigh Miller’s claims based upon all of the evidence including the testimony of the lay witnesses. The determination of functional disability is not limited to impairment ratings established by medical evidence. The commissioner should then reconsider and redetermine the benefits based upon the entire record and in accordance with the principles set forth in this opinion. The commissioner should also reconsider the assessment of costs, penalties, and interest.
Costs of appeal are assessed against the appellees.
DECISION OF COURT OF APPEALS VACATED; RULING OF DISTRICT COURT REVERSED AND CASE REMANDED TO THE INDUSTRIAL COMMISSIONER FOR RECEIPT OF ADDITIONAL EVIDENCE AND RECONSIDERATION.
All Justices concur except SNELL, J., who dissents, and is joined by McGIVERIN, C.J., and HARRIS and LARSON, JJ.