Power analysis: Ian Boswell’s epic race-winning ride at Unbound Gravel
After more than 10 hours in the saddle and 331 km in the legs, a two-up sprint between Ian Boswell and Laurens Ten Dam decided the Unbound Gravel 200 men’s race winner.
Both were former WorldTour pros, noted climbers, and debutants at the Unbound Gravel race. Neither was known for their sprinting prowess.
Boswell has posted his ride on Strava in the days since the race, but we wanted even more detail. He was kind enough to share with CyclingTips the power file from his Wahoo Elemnt Roam head unit and SRAM Force Quarq power meter.
We have taken a deep dive into that power file to see exactly what it takes to win such a gruelling race.
And “gruelling” is perhaps an understatement. The Unbound 200 is a real race of attrition, with the back door a bigger factor in the front group than stinging attacks. But more on that later.
(This post discusses power-to-weight ratios. To put these numbers into context, be sure to check out the linked article.)
Let’s start with an overview of the whole ride. While the 247-watt average might not seem huge for a gravel race, bear in mind this 247 W average is for 10 hours 14 minutes and from a rider weighing just 73 kg (3.38 W/kg). Add to that the truly bonkers 32 km/h (20 mph) average speed for 10 hours on gravel roads! Mind well and truly blown!
Some of the other overview numbers are just as startling. 280 watts Normalised Power* (NP) (3.84 W/kg), 2,724 metres of climbing, 9,107 kJ of work (read: calories burned), all at an average temperature for the day of 26 ºC (79 ºF).
(* Normalised Power is the amount of power the rider could have maintained had their power output been steady throughout the effort.)
While WorldTour races such as Milan-San Remo hit the same 300 km range as Unbound, the smooth tarmac surfaces and team tactics mean the speeds can be much higher. As such, sitting in the bunch for the first five hours of MSR is usually much less demanding physically than what is effectively an off-road group ride at Unbound.
The combination of tough terrain, unfinished surface, and a much-reduced drafting effect from a smaller group means riders spend much more time on the power at an event like Unbound.
In fact, if we filter out the first 75-90 minutes of Unbound where Boswell had just a couple of early efforts – presumably to jockey for position in the large bunch of starters – the numbers get even more impressive.
For the next almost nine hours of racing (read, torture), Boswell actually churned out an average of close to 260 W (3.56 W/kg) or 286 W NP (3.92 W/kg). Delve a little deeper into the power file, though, and we can see Boswell’s Variability Index (VI – a ratio of NP to average power) is just 1.11. Consider that riders would opt to save energy and power in such a long event whenever possible. Hence this VI is another indicator that Unbound requires an athlete to be on the pedals almost all day. Virtually zero coasting here.
For comparison, I checked a pro race I did in 2013 – I had a VI of 1.23. My Everesting [the fastest Everesting on record – ed.] had a VI of 1.14.
Early selections
As mentioned above, the first 60-90 minutes of the race were a relatively calm affair. That’s unsurprising given the riders had a full 10 hours (for the winner) of racing ahead of them.
The action started to heat up after this as the selection process began. In the next hour of the race Boswell hit peak powers for the race with efforts for 1 minute at 514 W (7.04 W/kg), 6 minutes at 354 W (4.85 W/kg), 10 minutes at 334 W (4.58 W/kg), 12 minutes at 328 W (4.5 W/kg), 20 minutes at 314 W (4.3 W/kg), 30 minutes at 302 W (4.14 W/kg) and 60 minutes at 295 W (4.04 W/kg).
The fact Boswell hit so many peak powers in this early phase shows the race was well and truly on. The front group’s back door never got a chance to shut, with riders seemingly dropping out of the rear constantly.
That one-hour block of intense action was fought out across a mixture of steep hills, descents, and rolling roads. The inclines were so steep Boswell was down to 12 km/h and mid-60s rpm, while down the other side he was hitting close to 70 km/h on some of the gravel descents.
Keep the chain tight! A full three hours at 277 W average, 310 W NP.
Boswell seems to have kept a cool head while the race was splitting up and that initial selection was being made. With such short steep inclines, it would be very easy to overcook the effort here, with potentially disastrous effects later in the race. Boswell did hit his peak one-minute power in this section, presumably in response to an attack, but his power file reflects that of a rider entirely in control.
The front group sustained this relentless pace over the next two hours, averaging 32 km/h as Boswell tapped out a strong 268 W (3.67 W/kg) average. That’s only part of the story, though, because during this period, more climbs, wind, and attacks whittled this front group down to just seven riders.
What a group it was, featuring former winners Colin Strickland and Ted King, former WorldTour riders Boswell, Ten Dam and Stetina, Rally Pro Cycling’s Robin Carpenter, and former UnitedHealthcare rider Eric Marcotte.
After a relentless three hours at 277 W average for Boswell, it was a surge as the riders tackled Little Egypt Road that finally drove this group clear and brought a 363 W five-minute effort out of Boswell – his peak five minutes for the day! If you think a five-minute effort at 4.9 W/kg doesn’t sound crazy impressive, try doing it at the end of three hours at 3.8 W/kg. Crazy stuff.
Time out
Shortly after this, the group was whittled down to just five as Marcotte and Carpenter were tailed off (it is unclear if this was due to fatigue or mechanicals). At this point the remaining five in the front, perhaps considering they still had 160 km to cover, seemed to call some sort of a truce. They even agreed on an aid station stop.
For the next three and a half hours, the average speed dropped to 29 km/h. Boswell’s average power for this section was 237 W (3.25 W/kg), for what may seem like a welcome bit of recovery. However, the riders were now over 200 km into the ride, and 7+ hours in the saddle, any drop-off in pace was unlikely to actually feel any easier.
This five-man group pressed on together over undulating gravel roads before eventually turning into a headwind in the final sections of the race.
Going clear
Few of the front group would want to risk a sprint in the finale of such a long and hard race. The race had been a war of attrition up to that point, with hundreds whittled down to just five in the front group.
Stetina attacked around 40 km to go. He drove clear and Boswell reacted with a series of efforts. First up was a 2:30 effort at 350 W (4.8 W/kg) with a peak of 584 W up Double D Hill, where Boswell actually took the KOM on Strava. This was immediately followed by a flat-out descent into another short, sharp kick and another punch hitting close to 600 W (8.2 W/kg).
Finally, he put in a two-minute effort maxing out at 469 W (6.42 W/kg) with an average of 333 W (4.56 W/kg) on Kahola hill. At just 630 metres in length with 38 m of elevation gain, this is not the sort of climb that would usually split such an illustrious front group, but this in Unbound. With over nine hours of racing completed and after a series of attacks, it’s safe to say this would have hurt, a lot!
With a mixture of headwind and crosshead for the final 40 km the odds were stacked against a solo move. The chase group got organised and, following another series of rider exhaustions and mechanical misfortunes, it was just Boswell and Ten Dam, alone, out front.
The two former WorldTour riders settled in for what was effectively a two-up time trial, averaging a mammoth 32 km/h and 264 W (3.62 W/kg) for the final 30 minutes of this 10:14 ride. Until, of course, they came into the final kilometre.
Then the cat and mouse began, neither rider wanting to launch the sprint too early in what would surely be the most tormented sprint either rider will ever attempt. Nevertheless, Boswell led out the sprint and somehow managed to unleash a peak of 1,032 W (14.1 W/kg) with a sustained 12 seconds at 938 W (12.85 W/kg) to hold off Ten Dam and take the win on the line.
It is this final sprint that is most impressive for me of the whole ride. I have raced a 300 km road race, a 555 km endurance event along the Irish Wild Atlantic Way, and completed three Everestings. Speaking from experience, I can tell you that while sustained efforts seven, eight, or nine hours into an event are tough, it is bursts of power, sharp accelerations, and sprints that become almost impossible.
While luck and avoiding mechanical issues undoubtedly play a role in surviving Unbound, Boswell and Ten Dam had the sheer power to blast through the dirt consistently for 10 hours straight. While none of the powers I have listed here would be anywhere near Ian Boswell’s all-time best efforts, it is the sustainability and repeatability that is truly impressive.
Boswell was cracking out efforts after nine hours very similar to those he was doing in those tough hours two and three. It is that endurance and fatigue resistance that earned him the top step. Oh, and a healthy measure of resilience, determination, calmness, and bike handling.
The Quadrant Analysis of Ian Boswell’s power file. This chart plots the pedal force on the y-axis and the pedal velocity or rpm on the x-axis. As we might expect from the power analysis Boswell was on the pedals a lot. More than half of that time was technically in the low cadence, low torque Q3 on the quadrant analysis. 
This graph shows the speed trend for the day. Unsurprisingly with 10 hours in the saddle and a headwind home, the speed declined as the race went on.
The post Power analysis: Ian Boswell’s epic race-winning ride at Unbound Gravel appeared first on CyclingTips.