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                                                                    Exhibit 4.20

                                  WAIVER NO. 1
                                       TO
                              BRIDGE LOAN AGREEMENT

         WAIVER NO. 1, dated as of October 23, 2002 (this "Waiver"), to the
BRIDGE LOAN AGREEMENT, dated as of June 25, 2002 (the "Loan Agreement"), among
CONCENTRA INC., a Delaware corporation (the "Borrower"), the Lenders (as defined
therein) and CITICORP NORTH AMERICA, INC. ("Citicorp"), as administrative agent
for the Lenders (in such capacity, the "Administrative Agent").

                              W I T N E S S E T H :

         WHEREAS, the Borrower has requested that the Lenders waive compliance
with provisions of Section 7.6 (Prepayment and Cancellation of Indebtedness) of
the Loan Agreement to permit the prepayment, in an aggregate amount not to
exceed $25,000,000, of term loans outstanding under the Operating Co. Credit
Facility in connection with a proposed issuance of Stock by the Borrower to one
or more of its current stockholders or their Affiliates; and

         WHEREAS, the Administrative Agent and the Lenders signatory hereto have
agreed to such waiver on the terms and subject to the conditions herein
provided;

         NOW, THEREFORE, in consideration of the foregoing premises and other
good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereto agree to the following:

     Section 1. Defined Terms. Capitalized terms used, but not otherwise
defined, herein have the meanings set forth in the Loan Agreement.

     Section 2. Waiver. As of the Effective Date (as defined herein), the
Lenders hereby waive compliance with the covenant contained in Section 7.6
(Prepayment and Cancellation of Indebtedness) of the Loan Agreement solely to
permit the prepayment on or prior to December 31, 2002 by the Operating Co., in
an aggregate amount not to exceed $25,000,000, of term loans outstanding under
the Operating Co. Credit Facility; provided, however, that the Borrower shall
have received an aggregate purchase price equal to the aggregate amount of such
prepayment from an Excluded Equity Issuance permitted by the Existing Debt
Documents to one or more holders of the Borrower's Stock or Stock Equivalents on
the Closing Date and their Affiliates.

     Section 3. Conditions to Effectiveness. This Waiver shall become effective
as of the date (the "Effective Date") on which the Administrative Agent shall
have received counterparts of this Waiver duly executed by the Administrative
Agent, the Requisite Lenders and the Borrower.

     Section 4. Representations and Warranties. The Borrower represents and
warrants to the Administrative Agent and each Lender as follows:

         (a)    After giving effect to this Waiver, each of the representations
and warranties in the Loan Agreement and in the other Loan Documents are true
and correct in all material respects on and as of the date hereof as though made
on and as of such date, except to

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the extent that any such representation or warranty expressly relates to an
earlier date and except for changes therein expressly permitted by the Loan
Agreement.

         (b)    After giving effect to this Waiver, no Default or Event of
Default has occurred and is continuing as of the date hereof.

         (c)    The execution, delivery and performance by the Borrower of this
Waiver have been duly authorized by all requisite corporate or other action on
the part of the Borrower and will not violate any of the articles of
incorporation or by-laws (or other constituent documents) of the Borrower.

         (d)    This Waiver has been duly executed and delivered by the
Borrower, and each of this Waiver and the Loan Agreement constitutes the legal,
valid and binding obligation of the Borrower, enforceable against the Borrower
in accordance with their terms.

     Section 5. Reference to and Effect on the Loan Documents. Except as
expressly provided herein, the provisions of the Loan Agreement and all of the
other Loan Documents shall remain in full force and effect and are hereby
ratified and confirmed. The execution, delivery and effectiveness of this Waiver
shall not, except as expressly provided herein, operate as a waiver of any
right, power or remedy of the Lenders or the Administrative Agent under any of
the Loan Documents or constitute a waiver of any provision of any of the Loan
Documents.

     Section 6. Costs and Expenses. The Borrower agrees to reimburse the
Administrative Agent and the Lenders for all reasonable fees, costs and
expenses, including the reasonable fees, costs and expenses of counsel or other
advisors for advice, assistance, or other representation in connection with this
Waiver.

     Section 7. Governing Law. This Waiver and the rights and obligations of the
parties hereto shall be governed by, and construed and interpreted in accordance
with, the law of the State of New York.

     Section 8. Headings. Section headings in this Waiver are included herein
for convenience of reference only and shall not constitute a part of this Waiver
for any other purposes.

     Section 9. Counterparts. This Waiver may be executed in any number of
counterparts and by different parties hereto in separate counterparts, each of
which when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same instrument. Receipt by the
Administrative Agent of a facsimile copy of an executed signature page hereof
shall constitute receipt by the Administrative Agent of an executed counterpart
of this Waiver.

                            [SIGNATURE PAGES FOLLOW]

                        [Signature page to Waiver No. 1]

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     IN WITNESS WHEREOF, the parties hereto have duly executed this Waiver as of
the date first above written.

                                Concentra Inc., as Borrower

                                By:        /s/ Thomas E. Kiraly
                                    ------------------------------------------
                                    Name:  Thomas E. Kiraly
                                    Title: Executive Vice President


                                Citicorp North America, Inc., as Administrative
                                 Agent and a Lender

                                By:        /s/ F.R. Lowe
                                    ------------------------------------------
                                    Name:  F.R. Lowe
                                    Title: Vice President


                                Credit Suisse First Boston, acting through its
                                 Cayman Islands Branch, as a Lender

                                By:        /s/ Christopher Lally
                                    ------------------------------------------
                                    Name:  Christopher Lally
                                    Title: Vice President


                                By:        /s/ Jennifer A. Pieza
                                    ------------------------------------------
                                    Name:  Jennifer A. Pieza
                                    Title: Vice President


                        [Signature page to waiver No. 1]