VaibhavN - Here is the link to substantiate claim made above:
http://www.cic.gc.ca/english/resources/tools/perm/express/intake-complete.asp
Mandatory documents for all applicants
The following documents are mandatory and must be provided by all applicants.
Applications that do not contain the following documents will be rejected as incomplete, and fees will be refunded accordingly.
Medical examination confirmation
Purpose
To assess the health of the applicant and their family members
Document requirements
The medical examination confirmation is required up front at the time of the application and must be valid for a minimum of six months.
The applicant must include the immigration medical examination (IME) number in their e-APR.
The applicant must provide a copy of either the information printout sheet or the Upfront Medical Report form [IMM 1017B (PDF, 453 KB)] (available internally only), whichever the panel physician provides upon completion of the medical examination.
Exceptions are made only in rare circumstances that are outside of the client’s control (e.g., cancellation of the appointment by the panel physician at the last minute without time to reschedule).
In exceptional circumstances, IRCC may accept
proof that a medical appointment is scheduled; or
a letter of explanation of best efforts.
However, these are not a guarantee of acceptance.
Individuals who must submit this documentation
The principal applicant
Their spouse or common-law partner
Their dependent children, including non-accompanying
Hope this clarifies that you should not submit your application until you are done with Medicals.
Another helpful links:
http://www.cic.gc.ca/english/information/medical/medexams-perm.asp
http://www.canadavisa.com/canada-immigration-discussion-board/medical-examinationmade-easy-t133692.0.html
Good Luck!!