JOHANNESBURG, South Africa -- A bearded and much skinnier Oscar Pistorius was "overcome with emotion" as he pulled on his carbon fiber running blades for his first track training since the killing of girlfriend Reeva Steenkamp, his agent says.

With a short beard and a blue hooded Nike sports top, the lean-looking double-amputee Olympian did some light jogging at his first formal session in around five months on Thursday. He then described his return to a regular track routine for the first time since he fatally shot Steenkamp at his home on Feb. 14 as "bittersweet" to his agent, Peet van Zyl.

"It was a very emotional experience for him to put the blades back on, to walk back onto the track, get the smell of the track," Van Zyl, who went to the track at the University of Pretoria with Pistorius, told The AP on Friday. "It was tough for him. He said to me it was like a bittersweet feeling and emotion for him to be back on the track."

Pistorius' return to training was seen in a brief video clip released by his family. In the footage, which is around two minutes long, the athlete is first sitting on a chair at his usual training track at the university pulling on his running blades. He then does some light jogging on the sunbathed track and, finally, wipes his face with both hands as he walks off the track, hinting at the emotion Van Zyl described.

Pistorius was charged with premeditated murder for Steenkamp's Valentine's Day shooting death. He denies murder and says he shot his girlfriend accidentally, believing she was an intruder in his house.

Pistorius' next court appearance is Aug. 19, when prosecutors may indict him and a date could be set for the start of his murder trial, possibly in September or October. He faces a life sentence with a minimum of 25 years in prison if he is convicted by a judge of premeditated murder. There is no trial by jury in South Africa.

South African police said the investigation into Pistorius' shooting of Steenkamp was "at an advanced stage," but declined to give further details, saying they "cannot be drawn into discussing the merits of the case."

Prosecutors have said police will conclude their investigations by August and continue to probe the circumstances of Pistorius' pre-dawn killing of Steenkamp, whom he shot multiple times through a toilet cubicle door.

In the last few months, the 26-year-old Pistorius has lost weight -- about 10-12 kilograms -- and spends much of his time doing household chores at the Pretoria home of his uncle as he awaits his murder trial, Van Zyl said. Pistorius looked much leaner in the video footage than he was at the London Olympics and Paralympics last year.

Pistorius telephoned Van Zyl and his coach, Ampie Louw, about a week ago to say he was ready to train again.

"(He) said, 'Guys I think I'm ready to resume training," Van Zyl said.

Van Zyl and Pistorius' family, who also released a statement along with the footage, said Pistorius' return to regular training was to help his own mental process ahead of a likely lengthy murder trial, and he was still not planning on competing anytime in 2013.

"His focus at this time remains entirely on the court case," the Pistorius family said. "His family and those close to him have encouraged him to spend a few hours a week on the track to assist him in finding the necessary mental and emotional equilibrium to process his trauma and prepare for the trial."

Thursday's visit was the second time Pistorius has been seen on the university track since he killed Steenkamp.

A March sighting spurred speculation he was back in training, which was denied by his family, who described him then as being in "an extremely traumatized state" and not willing to contemplate training at that time. Then, Pistorius was photographed by a schoolgirl on a cellphone while he was walking on the track, but he made that visit without the knowledge of anyone else, his agent said, and waited for a group of athletes he took to the track to leave before he put on his blades and just walked around.

His new routine will involve around three to four sessions a week and be run by Louw, Pistorius' longtime coach and the man who introduced him to athletics when Pistorius was a teenager and still at school.

Van Zyl said Pistorius had discovered he was desperately missing running and training.

"I think the emotions yesterday show how much he really did miss being back on the track and being able to run," Van Zyl said. "Obviously with the world championships, both Paralympic world championships and IAAF world championships getting closer, it's even tougher for him not be running or training or competing."