1991–2006

Lamaze began competing at the grand prix level in 1991^[2] or 1992.^[3] A year later, he was named to the Canadian equestrian team.^[2] His first major competition as a national team member was the 1994 World Equestrian Games.^[1]

Lamaze was named to the Canadian team for the 1996 Summer Olympics in Atlanta, Georgia, but lost his place and received a four-year suspension after testing positive for cocaine. Arbitrator Ed Ratushny overturned the suspension, although Lamaze had already missed the Atlanta Games when the ruling was delivered.^[4]

Lamaze rebuilt his career and ascended the rankings, being again regarded as a key member of the Canadian team for the Sydney Games. However he tested positive for a banned stimulant, which resulted in his removal from the team and facing a lifetime ban. Right afterwards, a despondent Lamaze contemplated suicide and while drunk he smoked a cigarette laced with cocaine. Forty-eight hours later, the test for the banned stimulant was reversed on appeal, however Lamaze then tested positive for cocaine which would also have meant a lifetime ban. Arbitrator Ed Ratushny overturned the cocaine test, but the Canadian Olympic Committee refused to reinstate Lamaze on the Canadian team.^[4]

2007–2011: Hickstead years

In 2007, Lamaze became the first Canadian jumping rider in 20 years to make the top ten in the world rankings. He was also the first North American jumping rider to exceed one million in prize money a year, a third of these earnings the result of winning the CN International Grand Prix at Spruce Meadows.^[5] The CN International Grand Prix was Lamaze's first major win with Hickstead.

Lamaze competed in the Beijing Olympics, riding the stallion Hickstead.^[6] He was awarded a silver medal after a strong performance in the team event.^[7] Lamaze went on to win a gold medal in the individual show jumping event of the 2008 Beijing Olympics at the Shatin Equestrian Venue in Hong Kong as a result of a jump off between himself riding Hickstead and the Swedish rider Rolf-Göran Bengtsson, riding Ninja.^[6]

In the January 2009 Rolex World Rankings for show jumping by the International Equestrian Federation, Lamaze was named to the top spot for the first time.^[8] In October 2009, Lamaze won the €120,000 Equita Masters in Lyon, France, riding Hickstead.^[9]

Lamaze returned to first place in the Rolex Rankings for July 2010. In July that year, he had two major wins with Hickstead, at the Aachen World Equestrian Festival^[10] and the Spruce Meadows Queen Elizabeth II Cup.

In 2011, Lamaze and Hickstead won the €200,000 Rome Grand Prix, the €200,000 La Baule Grand Prix, the Spruce Meadows Queen Elizabeth II Cup, the €23,000 1.55m in Rotterdam,^[11] the $1 million CN International Grand Prix, and the €100,000 Barcelona Grand Prix.^[12]

2012–2022

After the death of Hickstead in 2011,^[13] Lamaze selected the nine-year-old mare Derly Chin De Muze to ride at the 2012 London Olympics.^[14]

In July 2016, he was again named to Canada's Olympic team, serving as the leader following Ian Millar's decision to not compete again. Lamaze rode the Hanoverian mare, Fine Lady 5.^[15] As a member of Canada's jumping team, he competed in a climactic jump-off for the bronze medal, which was ultimately won by the German team. Later, he won a bronze medal in the individual jumping event, a single knocked rail preventing him from earning a second gold medal.^[16]

In 2017, Lamaze was diagnosed with brain cancer, which he revealed to the public in 2019.^[17] He continued competing for some time, winning a gold medal at the Spruce Meadows Masters tournament in June of 2019.^[18] In 2021, he announced that he would not seek to be part of the Canadian Olympic team for the 2020 Summer Olympics in Tokyo, saying that while his health was stable he felt there were too many risks.^[19] Lamaze's battle with brain cancer continued, and on March 31, 2022 he announced that he would be retiring from competition in order to focus on his health. He planned to remain as the Canadian showjumping team's chef d'équipe. After announcing his retirement, he said: "I've always said that I will retire under my own terms when the time is right. The situation with my health has forced me to make the decision earlier than I had envisioned, but the silver lining is that I still have the will to win and can contribute to the Canadian team and the sport I love through my new role."^[20]

Forgery of Cancer Documents

In August 2023, it was found that Lamaze had forged medical documents submitted to the Ontario Supreme Court.^{[21][unreliable source?]}

As a result of these findings, Lamaze's lifelong attorney, Tim Danson, stepped down as counsel.

It is alleged that Lamazes ongoing Cancer and alleged treatments during his career were faked by Lamaze in order to delay and avoid several ongoing court cases brought against Lamaze in relation to horse sale disputes.

In order to dismiss this allegation that his cancer and health issues are entirely faked, Lamaze would need to produce reliable medical evidence to prove his claims- Lamaze has publicly declined to do so, stating in an 11 September 2023 article:

“They want a doctor’s note; have they seen me? People were telling me to go home, every day for years, as I was so sick. People who have never seen me and don’t know, believe what they see online. I’ve always spoken the truth and will continue to.” 

Lamaze says he was unaware of letters and documents submitted to the court and cited issues such as data protection relating to his medical records, and the need to protect people who have treated him.^[22]