The current study aims to examine the potential effects of rolling a Myostorm ball on the trigger points in the upper back muscles.

The investigators will ask the participants to attend the laboratory in two sessions. They will seek the tender spots on the trapezius muscle. Then the participants will be asked to roll a Myostorm ball ( a small hard ball made of plastic with a layer of soft material cover) on their affected muscles. They will be tested for pain-pressure threshold (PPT), shoulder range of motion, electromyography (EMG), and force before and after the manipulation.

Inclusion Criteria:

• trigger points on the trapezius muscle

Exclusion Criteria:

• back injury

The data will be kept confidential, and the participant codes will be used to link individual data across the experiment sessions. Data will be stored physically and digitally in Dr. Behm's office.

Every reasonable effort will be made to ensure the participants' anonymity. They will not be identified in publications without their explicit permission. All data will be collected independently and kept confidential.

All data will be stored in hardcopy and password-protected digital copy in Dr. David Behm's office at the Memorial University of Newfoundland. Consent forms will be stored separately from participant data in a locked cabinet in Dr. David Behm's office. Data access will be limited only to our research team members.

Data potentially may be published in an online journal article. Published data will contain no personally identifying information.

Data will be kept for at least five years, as Memorial University's policy on Integrity in Scholarly Research requires.