Photos: The grueling, muddy Spartan Race challenge

Participants climb over an obstacle at the start of the Spartan Race at Calamigos Ranch in Malibu on Dec. 7, 2014.  (Genaro Molina / Los Angeles Times)

A woman completes a series of push-ups in the mud during the Spartan Race at Calamigos Ranch in Malibu on Dec. 7, 2014.  (Genaro Molina / Los Angeles Times)

Participants receive a little help while trying to scale the”inverted wall” obstacle during the Spartan Race at Calamigos Ranch in Malibu on Dec. 7, 2014.  (Genaro Molina / Los Angeles Times)

A woman laughs as she crosses over the “inverted wall” obstacle during the Spartan Race at Calamigos Ranch in Malibu on Dec. 7, 2014.  (Genaro Molina / Los Angeles Times)

Muddy participants make their way to the “slip wall” obstacle after climbing over the “inverted wall” behind them during the Spartan Race at Calamigos Ranch in Malibu on Dec. 7, 2014.  (Genaro Molina / Los Angeles Times)

A woman tries to run up a muddy incline during the Reebok Spartan Race at Calamigos Ranch in Malibu on Dec. 7, 2014.  (Genaro Molina / Los Angeles Times)

Alex Rylance, right, looks up as he begins to climb the ‘slip wall’ as fellow competitor John Mulcahy, left, catches his breath before embarking up the wall during the Spartan Race at Calamigos Ranch in Malibu on Dec. 7, 2014.  (Genaro Molina / Los Angeles Times)

Participants climb the “slip wall” during the Reebok Spartan Race at Calamigos Ranch in Malibu on Dec. 7, 2014.  (Genaro Molina / Los Angeles Times)

Participants wait their turn to compete in the rope climb as others get started during the Reebok Spartan Race at Calamigos Ranch in Malibu on Dec. 7, 2014.  (Genaro Molina / Los Angeles Times)

Participants take part in the rope climb challenge as others wait their turn during the Spartan Race at Calamigos Ranch in Malibu on Dec. 7, 2014. More than 5,200 people took part in the three-mile race which features several physically daunting challenges.  (Genaro Molina / Los Angeles Times)

Two women have some fun in the mud during the Spartan Race at Calamigos Ranch in Malibu on Dec. 7, 2014.  (Genaro Molina / Los Angeles Times)

Participants take part in a rope climb challenge during the Spartan Race at Calamigos Ranch in Malibu on Dec. 7, 2014.  (Genaro Molina / Los Angeles Times)

Two participants lead over the “fire jump” obstacle just before the Spartan Race finish line at Calamigos Ranch in Malibu on Dec. 7.  (Genaro Molina / Los Angeles Times)

A muddy group of participants celebrate as they cross the finish line during the Spartan Race at Calamigos Ranch in Malibu on Dec. 7, 2014.  (Genaro Molina / Los Angeles Times)