(a) An employer's liabilities and obligations under the Fair Labor Standards Act with respect to the “principal” activities his employees are employed to perform are not changed in any way by section 4 of the Portal Act, and time devoted to such activities must be taken into account in computing hours worked to the same extent as it would if the Portal Act had not been enacted.^[53] But before it can be determined whether an activity is “preliminary or postliminary to (the) principal activity or activities” which the employee is employed to perform, it is generally necessary to determine what are such “principal” activities.^[54]

The use by Congress of the plural form “activities” in the statute makes it clear that in order for an activity to be a “principal” activity, it need not be predominant in some way over all other activities engaged in by the employee in performing his job;^[55] rather, an employee may, for purposes of the Portal-to-Portal Act be engaged in several “principal” activities during the workday. The “principal” activities referred to in the statute are activities which the employee is “employed to perform”;^[56] they do not include noncompensable “walking, riding, or traveling” of the type referred to in section 4 of the Act.^[57] Several guides to determine what constitute “principal activities” was suggested in the legislative debates. One of the members of the conference committee stated to the House of Representatives that “the realities of industrial life,” rather than arbitrary standards, “are intended to be applied in defining the term ‘principal activity or activities’,” and that these words should “be interpreted with due regard to generally established compensation practices in the particular industry and trade.”^[58] The legislative history further indicates that Congress intended the words “principal activities” to be construed liberally in the light of the foregoing principles to include any work of consequence performed for an employer, no matter when the work is performed.^[59] A majority member of the committee which introduced this language into the bill explained to the Senate that it was considered “sufficiently broad to embrace within its terms such activities as are indispensable to the performance of productive work.”^[60]

(b) The term “principal activities” includes all activities which are an integral part of a principal activity.^[61] Two examples of what is meant by an integral part of a principal activity are found in the Report of the Judiciary Committee of the Senate on the Portal-to-Portal Bill.^[62] They are the following:

(c) Among the activities included as an integral part of a principal activity are those closely related activities which are indispensable to its performance.^[64] If an employee in a chemical plant, for example, cannot perform his principal activities without putting on certain clothes,^[65] changing clothes on the employer's premises at the beginning and end of the workday would be an integral part of the employee's principal activity.^[66] On the other hand, if changing clothes is merely a convenience to the employee and not directly related to his principal activities, it would be considered as a “preliminary” or “postliminary” activity rather than a principal part of the activity.⁶⁷ However, activities such as checking in and out and waiting in line to do so would not ordinarily be regarded as integral parts of the principal activity or activities.^[67]