This weekend I will be running the Darlington half marathon for the 7th time. This is probably the only half marathon where a good negative split is guaranteed, of course a runners friend (and enemy) gravity plays a large part in this. The first half of the Darlington half is predominately uphill which of course translates to the second half being predominately downhill, funny that. (being an out and back course.) This race, more than most, involves the runner taking account of the terrain and holding something back for the return leg when time can be made up very quickly on fresh legs. To waste too much energy on the outbound journey would negate the benefit offered on the return.

I’ve attached my race splits from last year when I scrambled home for a 6th place finish after sitting in 4th for most of the race, which would have been my best finishing position. No worries, it’s not like I blew up but a couple of ‘younger’ runners got me with less than 3k to the finish. Anyhow as you can see from the graphic below it really is a case of up 10 or so kilometres, a couple of kilometres to grab your breath before a 10k race to the finish with gravity as your co-pilot.

Of course I’m not saying the last 10k is a breeze by any stretch of the imagination. You have a bib on your chest (and a chip on your shoe) so you will be pushing yourself deep into the pain box and although it helps you are running down hill you are still racing.

So what other variables need to be taken into account when you’re racing ? Heat is the obvious first choice. A Runners Choice article on training in the heat and its affect is worth a read:-

As year-round runners facing myriad conditions, we all recognize that it’s harder to run well when it’s hot. Perceived effort is greater and race times typically suffer accordingly. Why does this happen? What happens to the body at a physiological level? And most important, how should we adjust workouts and race expectations to best weather the weather?It’s generally recognized that for every 10-degree increase in air temperature above 55 degrees, there’s a 1.5 percent to 3 percent increase in average finishing time for a marathon. (Translation: An extra 3 to 6 minutes for a 3:30 marathon with every 10-degree increase.) This slow-down occurs because heat impacts runners at a physiological level through various means, including dehydration, increased heart rate and reduced blood flow (and subsequently oxygen) to the muscles used for running.

SWEAT: THE DETAILS
Thermoregulation is how your body maintains a consistent internal temperature. When exposed to external heat, your body cools itself and maintains equilibrium via perspiration. Perspiration has a cooling effect on the body because it removes excess heat through evaporation. The rate of evaporation—and subsequently how well the body is cooled—changes depending upon humidity. When humidity is low, evaporation increases; when humidity is high, the rate of evaporation decreases and less cooling occurs.Sweating, while critical to cooling the body, leads to fluid loss. Dehydration from fluid loss has a profound effect on running performance—a loss of even 2 percent of body weight leads to about a 4-to 6-percent drop in performance. Furthermore, both temperature and humidity increase heart rate and amplify these effects. At 60 to 75 degrees, heart rate increases by two to four beats per minute. From 75 to 90 degrees, heart rate increases up to 10 beats per minute, and humidity increases it even more. Perceived effort is accordingly much greater as both the temperature and the humidity rise.Compounding things, when you sweat your blood volume decreases, less blood returns to your heart, less oxygen-rich blood reaches your working muscles, you produce less energy aerobically and you run slower for a given effort level. As it gets hotter this effect is exaggerated because the greater the amount of heat that needs to be dissipated, the greater the proportion of blood diverted to the skin. While the red blood cells contained in plasma don’t play a role in the cooling process, your body can’t separate the red blood cells (which carry oxygen) from the plasma—all are brought to the skin to induce a cooling effect. When oxygen is redirected via blood flow to your skin instead of your muscles, you have less energy to use for running, and your heart and lungs must work harder to compensate for the loss in oxygen. As you’ve experienced, this results in a higher heart rate at a set pace and the inability to maintain the same pace as on a cool day.WHAT TO DO?
How can you minimize the negative impact of heat on performance? Because of blood plasma’s important role in the cooling process, training alone provides a bit of adaptation, because a side effect of running is an increase in total plasma volume. This helps to explain why the fittest athletes (and likely those with the highest plasma volume) typically adapt more easily to heat.

In addition to regular training, running in hot conditions results in changes that make it easier to maintain a faster pace and cause perceived exertion to drop, including a higher blood plasma volume, increased sweat rate, decrease in salt in sweat, reduced heart rate at a given pace and temperature, and a quicker onset of sweating. These changes make it easier to perform in the heat and are noticeable after only a week or two of heat exposure.

Still, heat acclimatization can take you only so far during weeks-long stretches of sultry weather. Steve Sisson, assistant coach of women’s cross country and track at the University of Texas, knows well the impact that prolonged, inescapable heat has on distance runners. On particularly hot days, he encourages his athletes to adjust expectations and change their attitudes. He explains, “Heat really affects intensity. It is really hard to get up and excited in high heat environments. One of the things that I try to get my athletes to do is to approach any workout in the heat as a progression. Adjusting the level of effort or intensity based on what the body is signaling is a key lesson for any athlete to learn.”

While Sisson doesn’t change the number or length of repetitions in a workout, he does modify the workout by shifting the focus away from a certain time goal to running an equivalent effort. “If we are trying to hit mile repeats in 5:20 for a 10K workout, I will give my runners a time range of 5:20 to 5:30 and let them adjust based on how they feel,” Sisson says.

“Living in a hot part of the country means that we are never going to get away from the heat. If we adjust volume we won’t be competitive.”

Sisson encourages his runners to look for internal cues instead of fixating on split times. To make the adjustment easier if you’re particularly split-focused, on horrific heat days move your interval sessions off the track. Working out on an uncalibrated course is a sure way to ensure a shift to effort over time and this makes it easier to pay attention to internal feedback and perceived exertion and avoid being distracted or discouraged by slower-than-hoped-for splits.

RACING IN THE HEAT
Racing is uniquely taxing in any weather. Adding heat into the equation creates a competing interest and struggle within the body between powering such a strenuous effort and the need to cool the body. This means that you have to work even harder to cool yourself and is why a race will feel much worse than a workout in similar conditions.

Alan Culpepper, a two-time Olympian, is familiar with this tug of war. He faced gruesome conditions in the 2004 Olympic Marathon in Athens, with a starting temperature of 80 degrees. Thanks to smart preparation for and patience during the race, Culpepper placed 12th in a field full of faster runners. Here’s what helped him succeed.

1) ADJUST YOUR PREPARATION.
If you’re fortunate enough to anticipate less-than-favorable conditions for an event, preparation is key. Culpepper says, “Get your body used to losing heat more efficiently.” The summer before the Olympics, Culpepper wore a baseball cap and long-sleeved shirt on runs to help acclimatize. He also advises taking in more electrolytes two to three days before a goal race, staying as cool as possible before the race (cold sponges can be helpful) and running a shorter warm-up before a hot event to prevent loss of electrolytes, particularly if you’re running a longer event.

2) ADJUST YOUR EXPECTATIONS.
Says Culpepper, “You have to pay attention to perceived effort. It is important to recognize you will be slower than you hoped but effort is the determining factor.” He advises that you pay less attention to traditional feedback like splits and instead, “Listen to the feedback your body is giving you: Is your breathing heavier? How uncomfortable are you?”

3) ADJUST YOUR MINDSET.
Attitude is critical. Culpepper recommends, “Instead of getting discouraged, recognize that everyone is dealing with the same conditions and have faith in your preparations.”

It’s Not the Heat, Nor the Humidity

It’s the dew point. That’s the meteorological measure that best predicts how tough your summer running is going to be.

Simply put, the dew point is the temperature at which water condenses. The closer the dew point is to the air temperature, the more saturated the air is and the less perspiration can evaporate and help the body cool itself, resulting in extra stress on the heart and lungs as the body attempts unsuccessfully to cool itself. Accordingly, the dew point provides a strong indicator of how you’ll feel running and a useful tool in predicting how much performance will be impacted.

DEW POINT (°F)	RUNNER’S PERCEPTION	HOW TO HANDLE
50–54	Very comfortable	PR conditions
55–59	Comfortable	Hard efforts likely not affected
60–64	Uncomfortable for some people	Expect race times to be slower than in optimal conditions
65–69	Uncomfortable for most people	Easy training runs might feel OK but difficult to race well or do hard efforts
70–74	Very humid and uncomfortable	Expect pace to suffer greatly
75 or greater	Extremely oppressive	Skip it or dramatically alter goal

Next of course is wind, a Runner Connect article describes the affect of gradients best friend…

Research on Running in Wind

The first study we’ll look to was published way back in 1971 by L.G. Pugh, a researcher in London.1 In his experiment, he had his subject (there was only one, an international-caliber middle distance runner) run along a treadmill cleverly mounted inside a wind tunnel.

Pugh measured the oxygen consumption of his runner over a variety of running speeds and wind velocities.He found that oxygen consumption, and therefore energy cost, increases with the square of the airflow over the body. So, the performance hit of a 10mph wind is four times greater than that of a 5mph wind, and the additional resistance running into a steady wind at 5:40 mile pace is twice that encountered when running into the same wind at 8:00 mile pace. In an additional experiment, Pugh measured the oxygen consumption of his runner first while running alone into a headwind, then while running one meter behind another runner. Pugh’s study found an 80% decrease in wind resistance when drafting off another runner! This corresponded to about a 6% drop in oxygen consumption for the given pace. Pugh confirmed these findings by taking airflow measurements in the wake of a single runner, then computing the effective air resistance for a runner-shaped object one meter back. From his measurements, it appears that there is still some benefit from drafting even two or three meters behind another runner. In a later study published in 1980, C.T.M. Davies investigated the effect of headwinds and tailwinds on three subjects using a similar treadmill-in-wind-tunnel setup.2Like Pugh, he found that oxygen consumption increases (and therefore, performance decreases) proportional to the square of the wind speed.While a tailwind does aid performance significantly, you only “get back” about half of what you put into a headwind when you turn around and run with it at your back. But Davies rightly points out that this relationship is diminished slightly during outdoor running—on a treadmill, any tailwind that exceeds your running speed is wasted, as you must remain in place on the treadmill.

However, results from real-world track races make it clear that, even in over ground running, the benefits of a tailwind do not entirely offset the drawbacks of a headwind. Davies also demonstrates that a tailwind that effectively eliminates air resistance. What does that mean?

For example: If you are running 6:00 mile pace with a 10mph tailwind, a tailwind equivalent would increase your performance by about 6 seconds per mile. However: The equivalent headwind (6-minute miles into a 10mph wind) would slow you by about 12 seconds per mile. While this rule is rather rough and based on treadmill studies, it’s reasonably applicable to racing speeds for most road runners. Davies also conducted some crude measurements of “drafting” behind other runners and found his data in agreement with Pugh: Trailing another runner by a meter or so can remove up to 80% of the energy cost of air resistance, making it a very attractive decision on a windy day. According to Davies, a mile (on a day with no wind) tucked behind another runner is four seconds easier than running it alone!

Does running in the wind cool you down quicker?

One final consideration when it comes to wind is its effect on heat removal from the body.

As pointed out in a 2012 review of climatic effects on marathon running by Greg Spellman, air resistance affects not only the forces you have to overcome, but your body’s rate of cooling. While running with a tailwind certainly helps you move faster, the effect of running in “still air” on heat removal cannot be ignored. As far as I know, there has been little to no published research on this effect: to what extent does the increased heat retention in running with a tailwind detract from your running performance on a hot day? And conversely, how much does increased cooling from a headwind offset the increased wind resistance? Boston Marathon participants and organizers were ecstatic about the 15mph tailwind on a 63-degree day in 2011, which propelled hundreds of runners to personal records. But would participants in the 2007 Chicago Marathon, marred not only by 88-degree weather but a paltry 6 mph wind speed, have run better with a brisk wind to cool them?

We’ll have to wait on future research to answer that question.

How Will Windy Conditions Affect My Running?

We’ve seen how the basics of the effects of air resistance have been known to exercise physiologists for some time.

The performance hit from air resistance increases exponentially with faster running speeds and wind velocities, but fortunately, up to 80% of the performance decrement can be eliminated by drafting about a meter behind another runner. Additionally, using a very rough rule of thumb you can anticipate the effect of wind resistance in a road race: A “substantial” wind (i.e. one approximately equal to the pace you are running at) will set you back 12 seconds per mile with a headwind, and aid you by 6 seconds per mile with a tailwind.

Headwinds aren’t always your enemy, however, since a brisk wind can aid cooling on a hot day. When it comes to choosing where you want to race, keep these factors in mind. Check out the weather history for the area and see which way the wind tends to blow. Also try to enter races where you know there will be plenty of competitors running the same pace as you, so you can save some energy by “tucking into the pack” like a middle-distance runner in a track race.

Finally, make sure you take advantage of a tailwind when you’ve got one! These tips are known to many elite runners and meet directors, who take heat, wind, and the competitiveness of the race into account when planning when to attempt a new record. Some of the best races in the world are held on cool spring and summer nights, after the winds die down as the sun sets and a world-class field toes the line.

So that sums up some factors to take into account when racing, gradient, heat and wind. Of course there are many more including how you feel on the day, previous weeks sleep patterns, previous weeks/months training distances, race importance (is this a goal race?), rain, conditions of the course (I.e trail or concrete). The list is long and just about endless, of course I’ll cover each eventually but for the moment I’ve got a race to prepare for.