FARGO — Prosecutors have accused a personal trainer in Fargo of grinding against a woman’s rear end and masturbating in front of another woman after recruiting them to be part of so-called medical studies.

The trainer, 27-year-old David Edward Sayler, was charged Friday, June 21, in Cass County District Court with sexual assault and disorderly conduct, both misdemeanors.

Sayler is the owner of Summit Fitness , 5171 51st Ave. S. in Fargo, which provides hockey training, as well as youth and senior fitness classes. Reached by phone Friday, Sayler referred questions to his attorney, Cash Aaland, who declined to comment on the case.

Court documents allege David Sayler separately asked two women to take part in studies for Alzheimer’s and that he asked another woman to participate in a Parkinson’s study. Two of the women agreed to do so, and the third woman declined, according to documents.

Sayler was working as a personal trainer at Edge Fitness, 6207 53rd Ave. S. in Fargo, when police took a report about him on Feb. 28. Messages left with owners of Edge Fitness on Friday were not immediately returned.

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One victim told police that when Sayler asked her to take part in the study, she said no but “Sayler was persistent in asking her to participate in the medical trial,” court documents stated.

The victim said Sayler demonstrated by walking up behind her, grabbing her waist and pulling her rear end into his midsection for one to two seconds before she repeated she was not interested, according to court documents.

The same victim told police that in January, Sayler confronted her in a laundry closet at Edge Fitness and locked the door. The victim told police “she was scared and shook the whole time."

"She didn’t feel like she could say no, so when he asked her to participate she agreed,” court documents stated.

Sayler then grabbed and massaged the victim's buttocks for three minutes, court documents stated. The victim told police she had not previously told anyone about the incident because “Sayler said the (medical) trial threatened arrest for disclosure to anyone,” according to documents.

The other alleged victim was a client of Sayler’s who told police she took part in a study Sayler claimed was for Parkinson's research. The victim told police she pressed her buttocks against Sayler for a period of time and then he would do pushups. As Sayler lay on the ground, she was on top of him facing away, court documents said.

At one point, the victim told police Sayler asked “what color her underwear was,” court documents stated.

This client at some point went to Sayler's business in south Fargo. She told police Sayler sat on a couch masturbating while she was lifting weights before she “grabbed her coat and left and was bawling and said it was the worst feeling,” according to court documents.

Sayler's alleged offenses occurred between Oct. 1 and Feb. 28.

The third woman who declined to participate in Sayler’s so-called study shared her experience with The Forum, which does not typically name victims of sex offenses.

She said Sayler first approached her in February. From the beginning, she said she felt “weird vibes” from him, and her suspicions heightened when he asked her if she would be interested in the study.

She said Sayler told her he was working on a secret government study and that he was one of 25 fitness professionals taking part. She said he told her the study — all video-recorded and documented — involved a fitness professional putting on a heart rate monitor before receiving some sort of “stimulus.”

But he told her that he was having difficulty with the “stimulus,” claiming he tried with his girlfriend but that he’s seen her naked too many times so it doesn’t increase his heart rate.

"I am sorry, but I am not your girl. I cannot do that," she told him.

She said that as an alternative, Sayler asked her to be the professional who is stimulated, and she again said no. She said she felt violated and thought the study seemed crazy.

The next day, she told her boss about Sayler, who was then fired, she said.

She had a feeling Sayler had done this before, so she asked another woman who knew about Sayler’s study. Once her boss was aware of Sayler targeting another woman, they contacted police.

Months after the experience, the woman told The Forum she felt like she was in "The Twilight Zone."

"I was questioning it over and over in my head,” she said. “It sounded so real and so confident with how he delivered it.”

Prosecutor Tracy Hines said she cannot speculate on whether Sayler will face additional charges or whether more victims will come forward, adding that the case is pending and the defendant has the presumption of innocence.

Sayler, who's not in custody, is set to be arraigned in court July 12.