Plaintiff-appellant Odis F. Anton seeks judicial review of a negative finding of the Full Industrial Board *420of Indiana denying his claim from compensation for permanent partial impairment.
The facts disclose that on March 9, 1978, appellant and a co-worker were moving an old sewing machine to make preparations for the installation of a new machine. While attempting to lift the machine, “one of the ends slipped.” Within a few minutes appellant experienced pain in his right lower back and hip area. Subsequently, appellant underwent surgery for the removal of a herniated intervertebral disc at L-5, S-l on the right side.
The facts further disclose that in 1969 appellant had a disc removed at L-4, L-5 and L-5, S-l on the left side. This surgery was necessitated as a result of an injury received in another employment and for which workmen’s compensation was paid by the former employer.
On September 8, 1972, appellant was hospitalized with low back pain with a slight amount of right sciatica.
The Full Board awarded appellant temporary total disability benefits and medical expenses. The Board further found that appellant does have a permanent partial impairment to the man as a whole, but that in light of the medical evidence presented “it cannot be determined as to whether such permanent partial impairment is due to his injury of March 9, 1973 or to the 1969 or 1972 incidents above referred to, and accordingly, no permanent partial impairment is found to relate to the accident in question, the plaintiff having failed to sustain his burden of proof in this regard.”
Appellant contends that the award of the Industrial Board is contrary to law. When reviewing the record on an appeal from the Industrial Board, this Court may consider only that evidence most favorable to the findings of the Board, together with the reasonable inferences to be drawn therefrom. Lincoln et al. v. Whirlpool Corp. (1972), 151 Ind. App. 190, 279 N.E.2d 596. Further, it is not our func*421tion to determine the credibility of witnesses or weigh the evidence heard by the Board to determine for whom it preponderates. Martin v. Monsanto Company (1975), 165 Ind. App. 5, 333 N.E.2d 828. This is an appeal from a negative award of the Industrial Board and may be reversed only if it appears that the Board’s decision was erroneous as a matter of law. Lincoln et al. v. Whirlpool Corp., stipra. Thus, an appellant must show that the evidence before the Industrial Board was without conflict and was so conclusive in nature and character as to lead to but one conclusion in the minds of reasonable men, and that the Industrial Board reached a contrary conclusion. Davis v. Webster (1964), 136 Ind. App. 286, 198 N.E.2d 883.
Dr. Aristides P. Papadopoulos testified that in his opinion appellant sustained a 15% permanent partial impairment of the man as a whole as a result of the surgery of May 17, 1973. Appellant contends that the evidence leads solely to the conclusion that the impairment, if any, which existed as of March 9, 1973, was agravated by the compensable injury which occurred on March 9, 1973. Appellant thus concludes that he was entitled to compensation under the principle that where an accidental injury, arising out of and in the course of employment, aggravates, accelerates, or activates a preexisting condition of or injury to an employee, the result is compensable. See, Earhart v. Cyclone Fence Co. (1934), 99 Ind. App. 48, 190 N.E. 558.
Although Dr. Papadopoulos testified that appellant was 15 % permanently partially impaired as a result of the May 17, 1973 surgery, he further testified that, in his opinion, part of the 15% rating existed before March 9, 1973. Moreover, he could not determine how much of the 15% existed before March 9,1973.
Dr. Wiliam A. Stark testified that in his opinion appellant has a permanent partial impairment of 8% of the man as a whole. However, he, too, could not determine how much of his *4228% impairment rating was due to the injury of March 9, 1973, or to the incidents of 1969 or 1972.
Since the medical testimony indicates that appellant was permanently impaired before the occurrence of the accident here in question, a competing principle to that urged by appellant is drawn into consideration. IC 1971, 22-3-3-12 (Burns Code Ed.), provides as follows:
“Subsequent permanent injury — Aggravation—Amputation. — If an employee has sustained a permanent injury either in another employment, or from other cause or causes than the employment in which he received a subsequent permanent injury by accident, such as specified in section 31 [22-3-3-10], he shall be entitled to compensation for the subsequent permanent injury in the same amount as if the previous injury had not occurred: Provided, however, That if the permanent injury for which compensation is claimed, results only in the aggravation or increase of.a previously sustained permanent injury or physical condition, regardless of the source or cause of such previously sustained injury or' physical condition, the board shall determine the extent of the previously sustained permanent injury or physical condition, as well as the extent of the aggravation or increase resulting from the subsequent permanent injury, and shall award compensation only for that part of such injury, or physical condition resulting from the subsequent permanent, injury. Provided further, however, That amputation of any part of the body or loss of any or all of the vision of one or both eyes shall be considered as a permanent injury or physical condition.”
This statute requires the Industrial Board to first determine the fact of a permanent injury and the extent thereof. It must then determine whether the injury is a subsequent permanent injury. If the Board finds that the injury is a subsequent permanent injury, it must then determine the extent of the previously sustained permanent injury or physical condition, as well as the extent .of the aggravation or increase resulting from the permanent injury. An award of compensation is made only for that part of such injury or physical condition resulting from the subsequent permanent injury. Kinzie v. Gen. Tire & Rubber Co. (1956), 235 Ind. 592, 134 N.E.2d 212.
*423The application of the statute extends to instances where, at the time of the accident, the claimant is already suffering an impairment or disability in the affected members as opposed to instances where he merely has a physical condition which renders him more susceptible to being injured. Bethlehem, Steel Corporation v. Cummings (1974), 160 Ind. App. 160, 310 N.E.2d 565 (transfer denied). See also, Small, Workmen’s Compensation Law, § 9.9, at 92-93 (1976 Cum. Supp.), wherein it was noted that the aforementioned statute is generally applied to cases involving successive harms of the type set forth in the schedules of IC 1971, 22-3-3-10 (Burns Code Ed.), while the cases dealing with the other types of aggravation of pre-existing condition have involved unscheduled harms which are not permanent injuries.
The evidence and reasonable inferences are that appellant had sustained two previous injuries that had resulted in permanent partial impairment to the man as a whole. The Industrial Board therefore could not base its award upon a final impairment evaluation of all three incidents. Moore v. Staton (1950), 120 Ind. App. 339, 92 N.E.2d 564. Appellant failed to carry his burden of proof in demonstrating what percentage of the permanent injury preexisted, and, thus, what percentage was caused by the accident for which compensation is sought. Without such evidence, the Board could not fulfill its duties as outlined by the statute. In light of this absence of evidence, the Board properly denied an award of compensation. The award of the Industrial Board must therefore be affirmed.
Award affirmed.
Staton, P.J., concurs in result; Garrard, J., dissents with opinion.