Nairobi — As the norm, Kenyans dominated the athletics world in 2017 from track to road races with Geoffrey Kamworor, Hellen Obiri, Eliud Kipchoge and Joyciline Jepkosgei igniting the season with their exceptional performance.
Men's half marathon
Being a non-World Championships year for the half marathon, two-time champion Kamworor pursued other events.
But nowadays there are so many international half marathons that lacking a global championship doesn't noticeably affect the statistical quality.
Three sub-59-minute runners and another 20+ running sub-60s actually made 2017 one of the best years ever.
The Copenhagen Half Marathon - which was born out of the successful World Half Marathon Championships held in 2014 in the Danish capital - has quickly developed into one of the world's highest quality races at the distance.
This year it provided all the sub-59-minute performances as the top three - Abraham Cheroben, Jorum Okambo and Alex Oloitiptip - finished in that order in 58:40, 59:48 and 58:51 respectively to move to third, eighth and 10th on the world all-time list. And they were followed by four more runners under one hour.
The upcoming World Half Marathon Championships host, Valencia, has already established itself as a top half marathon.
In the past seven years there have been a total of 21 sub-60-minute performances in Valencia with Cheroben having the course record with 58:48 since 2014. Cheroben also won this year, now running 59:11.
Besides Copenhagen and Valencia, New Delhi (five), Ras Al Khaimah (four) and Usti nad Labem (three) also had more than two sub-60-minute finishers this year.
The two largest half marathons - GöteborgsVarvet in Gothenburg and the Great North Run in South Shields - saw the winners this year finishing just outside 60 minutes: Geoffrey Yegon 1:00:19 and Mo Farah 1:00:06 respectively.
Before the 2007 Berlin Marathon, there had been just one sub-2:05 race ever. That number now stands at 29.
The 'sub-2:05 club' has grown from two to 33 members and the world record is sub-2:03. All but one of the 10 fastest marathons of all time have been run from 2011 onwards while all but one of the 10 fastest 10,000m track races date back to 2006 or earlier.
This marathon revolution ignited discussions about the possibility of running 26.2 miles within two hours.
An attempt to achieve that feat was organised at the Monza Racetrack in May, although various conditions meant it was not a ratifiable competition.
Olympic champion Eliud Kipchoge came close to the target but ultimately just missed out by less than half a minute.
The current official world record appears vulnerable, though. Five runners have PBs within just 16 seconds - 0.2% - of Dennis Kimetto's 2:02:57. No other world record is even close to having that kind of tight opposition.
Kipchoge, the two-time winner of the Berlin and London Marathons, is the main candidate to take down the record. His only loss in nine official races was to a world record in 2013.
But surprises are always possible; when Kipchoge won this year's Berlin in a world-leading 2:03:32, he was shadowed almost all the way to the finish line by unheralded marathon novice Guye Adola.
Although he had won the Boston Marathon earlier in the year, Geoffrey Kirui had the slowest PB and season's best of the three Kenyan entrants for the World Championships Marathon, but he emerged as the eventual winner in a thrilling seesaw battle with Ethiopia's Tamirat Tola over the last third of the race.
It was business as usual as there were different Kenyan winners in all top international marathons with Chicago (Galen Rupp) and Dubai (Tamirat Tola) the exceptions.
Men's other distances
Even though marathons and half marathons are the big mass races, the 10km probably has become the most popular road distance as measured in number of races and total number of participants.
This has created a new breed of specialists, led by Kenya's Benard Kimeli who during his first year on the international stage compiled four sub-28-minute performances, including the world-leading mark of 27:10 set in Prague in September.
Men's cross country
The intensive year-round road season has clearly affected the number of runners pursuing a full cross country season during the winter months.
There had been no international confrontations of the top contenders before the IAAF World Cross Country Championship Kampala 2017 held in the Ugandan capital in late March.
Reigning champion Kamworor, for example, had only run the Kenyan Trials where he had finished third behind Leonard Barsoton and Bedan Karoki.
During the past couple of decades, the World Cross Country Championships had evolved into a prestigious head-to-head between Kenya and Ethiopia. But this time the host nation Uganda had obviously prepared to make an impact.
Joshua Cheptegei - still only 20 - pushed the pace hard after four kilometres. Leading by a sizeable 12-second margin going into the fifth and final two-kilometre lap, he looked to be heading towards a big win.
However, with just one kilometre to go, Cheptegei hit the wall in dramatic fashion. Even though the Ugandan finished the race, he lost almost two minutes to defending champion Kamworor and dropped all the way down to 30th place.
Kenya got the two top medals individually while Ethiopia took the team title by one point (21 vs 22) thanks to a more compact team.
The overall East African domination was as strong as ever with 31 of the top 32 - Australian Pat Tiernan in 13th being the only exception - born in that region.
Women's half marathon
The season started fast with world half marathon champion Peres Jepchirchir winning the Ras Al Khaimah Half Marathon in a world record of 1:05:06, taking three seconds off the previous record set by Florence Kiplagat in 2015.
But just as Jepchirchir was beginning to establish herself as the dominant force over 13.1 miles, she was usurped by compatriot Joyciline Jepkosgei.
The 24-year-old had personal bests of just 1:09:07 for the half marathon and 31:08 for 10km at the start of the year, meaning the African 10,000m bronze medallist was still a relative unknown heading into 2017.
But after the Prague Half Marathon in April, everyone in the athletics world suddenly became aware of her.
Jepkosgei led through 10km in the Czech capital in a world record of 30:04 before going on to set world records at 15km (45:37) and 20km (1:01:25) before crushing the half marathon world record with 1:04:52, the first sub-65-minute performance in history by a woman.
Later in the year, Jepkosgei headed to Valencia and shaved a further second off her world half marathon record.
Her opening pace was more conservative than it was in Prague, but only slightly; she passed 10km in 30:07, 15km in 45:57 and 20km in 1:01:28. By the finish line, though, she was back on world record schedule and won in 1:04:51.
Mary Keitany broke the women-only world record, winning in London in 2:17:01, cutting one minute and 36 seconds off her previous PB, also set in London for a win five years earlier in 2012.
The 35-year-old Kenyan was 41 seconds faster than Paula Radcliffe's previous record from her victory in 2005.
In her second marathon of the season, the 2009 world half-marathon champion was beaten in New York where Shalane Flanagan grabbed the first win by a US woman since Miki Gorman's victory in 1977.
Flanagan, 36, has now completed 10 marathons. This was only her second win, following her triumph at the 2012 US Olympic Trials.
Ethiopian Tirunesh Dibaba also had an impressive season, clocking two sub-2:20 marathons. The 32-year-old finished second in London behind Keitany in a 2:17:56 national record and then won in Chicago, clocking 2:18:32 in her third marathon.
Many of the top names opted out of the IAAF World Championships marathon in London in August, but it was still an exciting race.
Having finished second to Edna Kiplagat in Boston, 2:21:52 to 2:22:51, Bahrain's Rose Chelimo swapped positions with the Kenyan veteran at the World Championships to win gold in 2:27:11.
Kiplagat, 38, took the silver medal in 2:27:18 to add to the gold medals she won in 2011 and 2013. USA's 33-year-old Amy Cragg just lost to Kiplagat in a sprint finish, but earned her first major medal, a bronze, and was timed at 2:27:18.
Women's other distances
The six fastest 10km times in history have all been set this year.
In between her world records for the half marathon, Jepkosgei returned to Prague in October for the Birell 10km race where she broke another magical barrier and set another world record.
The Kenyan clocked 29:43, the first ever sub-30-minute performance in this event and her second world record of the season at 10km.
During both of Jepkosgei's record-breaking performances at 10km, she dragged other women to some of the fastest times in history.
Violah Jepchumba went through the 10-kilometre checkpoint in 30:05 at the Prague Half Marathon, while Fancy Chemutai - another athlete who was unheralded before 2017 - finished second at the Birell Grand Prix in 30:06.
Both of those performances were well inside the pre-2017 world record of 30:21 set by Paula Radcliffe in 2003.
Women's cross country
Kenya and Ethiopian logged wins at all of the IAAF Cross Country Permit meetings prior to the IAAF World Cross Country Championships Kampala 2017 in March.
Each of the races were, however, won by different athletes and the field was quite open before Kampala.
Irene Cheptai recorded good wins in Albufeira at the European Champions Club Cup and at the Kenyan Championships in Nairobi.
It came as no big surprise when she won the senior women's race in Kampala, but the fact that Kenya filled the first six places was a shock.
Having just missed out on a medal in the 10,000m at the 2016 Olympics, Alice Nawowuna took the silver in Kampala, while 2013 world U18 3000m champion Lilian Rengeruk earned the bronze.