The Science Behind a Half Marathon Peaking Strategy: Reflections From My Taper and Carbohydrate Loading Strategy
Life has been flying by these past couple months. Between training, graduate school, and coaching, writing has been pushed into the background. But, after months of developing aerobic capacity, refining my running economy and pace control, trialing fueling strategies for performance, and learning more than I thought I would about endurance physiology, I am finally peaking for my second half marathon.
If you haven’t been keeping up with this endeavor recently, this might catch you off guard. ‘I thought you were bodybuilding? What happened? Well, to be honest – I needed a break. A decade of training for one goal, 3 years of competing, and my body was spent. Especially with my renal issues, it was time to take a breather. So, I decided to pursue some other athletic goals. I did this in hopes of learning in areas I had yet to explore deeply, develop my self-understanding, and strengthen my return to bodybuilding with a refreshed mindset.
To keep me engaged and challenged, I decided why not learn about endurance sport by throwing myself in the mix. I chose this for a few reasons: it’s fascinated me for the last few years coaching it, it’s an area of fitness I’ve neglected for years, it has a wonderful community, it’s adaptations are the closest to opposing bodybuilding, I have theories that it may aid in my renal health to support longevity in training, and It’s an accessible form of activity for my clients and as a student. So, I venture forth; I have booked a few endurance-based events over the next 6 months to continue this journey and hopefully share some of what I learn here.
Now full disclosure, although I am a clinical exercise physiologist and have been working within and studying exercise science for years, I am a newbie in the world of endurance sport. So, my knowledge has some crinkles one really doesn’t iron out unless they’ve been dedicated and focused on developing that knowledge. But, I do know how to read and translate research in a way that is hopefully easy to understand, and I do know how to adhere to a plan. So, this blog is meant to be a read as a type of learning note/case study; a place where I can blend my experience through this journey with evidence-based education. I will most likely have adjustments to my peaking strategy come my full marathon based on how I respond to this and any new research I come across. Even writing this blog is a big part of why I am doing this, because it forces me to justify and plan my decisions keeps my learning attuned.
** This is not individualized advice, but a critical analysis of the research and a series of personal reflections. If you are looking to make changes to your exercise or nutrition plan, you should be working with someone qualified on an individualized approach.
I’ve been yapping long enough, let’s get into this peaking plan.
What is Peaking and Why Does it Matter?
Peaking matters in any physical pursuit with an event or competition: martial arts, Olympic sprinting, skateboarding, or even bodybuilding. After months of training hard for a specific display of physical ability, you need to lower the accumulated fatigue, recover completely, rebuild any lost ability, and then manipulate your physiology, so you are prepared for what’s to come.
Surprisingly, peaking in endurance sport seemingly has a lot of overlap with my previous experience in bodybuilding, minus the spray tan prep and hunger-management. Entering a race dehydrated, over-rested, fatigued, depleted, over fueled and bloated, or under fueled can not only damage performance but make for an unenjoyable experience. After working so hard, you want to feel good and go have fun! A properly structured and well-flushed out peaking plan could improve performance by anywhere from 2-3% in elite endurance athletes, and possibly up to 8% in beginner to intermediate athletes. This might not sound like a big amount. But for the average half marathoner running a 2-hour long race, this could mean anywhere from 2-10 minutes off your total time. If that doesn’t sound like a big deal, it could also mean the difference between throwing up breakfast halfway through the race or not. Now that 2-8% is a rough estimate based on current research for tapering training load alone. So, it can be substantially larger when you factor in things like sleep, nutrition, hydration, and more.¹,²,³,⁴
Today we’ll be diving into the peak from two lenses. First, the research is around objective peaking strategies such as carb loading and tapering. Then, my experiences and reflections around how applying these to my context went. For the sake of time, this discussion will be limited to those two aspects of a peaking plan, and doesn’t include things such as pacing strategies, race-day nutrition, or fuel and hydration during the event.
The Science Behind The Taper
A taper is the deliberate reduction in training load leading into a race. Its purpose is straightforward: allow accumulated fatigue to dissipate without losing the adaptations built during training. A good taper also supports glycogen restoration, which becomes especially relevant once you begin thinking about loading. Because of that, it’s worth anchoring the discussion here first.
Tapering strategies within endurance sports vary widely by event and athlete. A small 2014 survey of elite runners highlights this clearly: middle-distance runners (800–1500m) and long-distance runners (3000–10,000m) tended to use a 6-day taper, while marathoners leaned toward 14 days (Mujika et al., 2014). This supports the general idea that shorter events prioritize maintaining sharpness, whereas longer events require more accumulated recovery.⁵
Even with this general principle, there’s still no universal “best” taper. Most studies land on the same structure of reducing total volume but maintaining intensity, yet the exact reductions and timelines vary. That variability was shown in a 2021 analysis of over 150,000 marathoners using Strava data. Longer, more disciplined tapers (up to 4 weeks) were linked with better race-day performance (Kiely et al., 2021). Interestingly, only about 31% of runners in the dataset executed a strict taper, even though the performance benefit roughly doubled compared to relaxed strategies.⁶
One amusing takeaway from the same dataset: male runners paced far more aggressively than female runners and were more likely to start too fast. The authors suggested many men might benefit more from better pacing than from perfect peaking. A humbling thought for many of us.
How much and how long?
In a recent meta analysis from 2023, it was shown that endurance athletes see meaningful improvements in time-to-exhaustion when tapering is structured around a drop in total training volume by 40-60%, but while maintaining training intensity and frequency.⁷
The previous Strava-data study showed up to 4 weeks of tapering being beneficial, but other studies suggest anywhere from a few days to 3 weeks, capping out at 21 days. However, the 40-60% reduction in total volume holds true.
The impact of previous training load and accumulated fatigue, along with race distance, likely impacts the taper needs. Specifically for runners, some research suggests that more tapering may be needed compared to other sports with lower impact forces such as cycling.⁸ Although this research has a small sample size and is quite old.
Why Some Older “Pre-Taper Overload” Ideas Lost Favor
Historically, some taper protocols involved a brief ramp-up or “overload” just before the taper began. The theory is that a final high training load followed by rest would amplify the rebound effect.⁹
More recent reviews and analyses have largely moved away from that approach for endurance runners. Instead, they emphasize entering the taper already stabilized, not in a state of fatigue or overload, because overload can impair recovery and blunt the taper’s benefits.¹⁰ I feel from a practical sense, this may also increase the risk of overuse injuries which would impact performance negatively.
In short, increasing volume pre-taper is unnecessary and may even be counterproductive, especially if you already have a consistent training schedule.
Maintaining Intensity for Performance
One of the clearest aspects of taper research is that intensity should not be cut from the plan. Training stress should drop because weekly miles, kilometers, or minutes decrease, not intensity.
The role intensity plays into your current training should be held consistent. For example, if your normal training week has 30 minutes of work at >85% VO2max or ‘intense’ sessions, that should continue into the taper. This could easily be expressed as kilometers.
However, how these more intense kilometers are implemented may look different, because the runs are changing. To continue recovery and still maintain neuromuscular sharpness, it may be more beneficial to break these faster kilometers up progressively as the taper progresses, so one session doesn’t have too much of a focused, high workload. For example, instead of performing 5km back-to-back at a high intensity, adding 3 fast kilometers to a single day and 2km to another may be more conducive to the recovery goals of the taper plan.
This fits into broader taper frameworks described in the previously mentioned research.
My Taper Approach
I followed a strict 14-day taper with a progressive, stepwise reduction in total training volume. My first week of tapering was roughly 60% of my usual weekly mileage, dropping from about 30 kilometers to 20 kilometers. The second week cut further to around 30%, ending at roughly 10 kilometers for the week pre-race.
Cross-training added another layer of complexity. I was typically doing 2–3 hours per week, so I reduced that progressively alongside the running volume, going from three hours to two, then two to one hour. The goal was to bring my total weekly workload down while maintaining the taper structure.
During my runs, I kept some intensity in the plan. I included periodic fast kilometers and shorter runs at race pace to preserve neuromuscular sharpness and maintain some high-intensity stimulus, even as total volume declined.
For strength-work, I scheduled this as a typical bodybuilding taper-plan. I stopped training legs a week out to allow for a full recovery and then trained upper once the week prior at 70% intensity. I then allowed for 72 hours between my final upper session and the event.
Areas for Improvement
Looking back, I’d adjust a few things next time. I’d spend more time in Zone 2 to maximize recovery while incorporating even sharper bursts of high-intensity kilometers. This would ideally allow me to maintain fitness, neuromuscular readiness, and race-specific adaptations without overly depleting muscle glycogen. That said, my carbohydrate loading strategy likely mitigated much of the glycogen depletion, which we’ll cover next. For the marathon, I expect to drop training for 4 weeks in total using a progressive linear taper. I also expect to drop resistance training earlier and allow for a full week of strength-training recovery.
Carbohydrate Loading: The Science
Carbohydrate (CHO) loading is a well-known strategy for increasing muscle glycogen stores in the 24–72 hours before an endurance event. Higher glycogen availability theoretically supports prolonged work output and delays fatigue. However, despite its widespread use, finding solid recent research is surprisingly difficult. Classic studies showed that manipulating CHO intake increases muscle glycogen content and improves time to exhaustion.¹¹ But since the 1960s, these methods have been refined substantially.
Glycogen Amounts and Sex Differences
A trained endurance athlete can typically store ~350–700 g of muscle glycogen and ~75–100 g of liver glycogen, depending on muscle mass, training status, and diet. These stores fuel moderate-to-high-intensity exercise, where carbohydrate use is high.¹²
At intensities around 70–85% of VO₂max, both men and women rely heavily on carbohydrate oxidation. Historically, women were believed to use less glycogen at a given relative intensity and rely more on fat oxidation.¹³ This may still hold in certain scenarios, but more recent research shows the differences are small and highly dependent on diet, energy intake, training status, and menstrual cycle phase.
Earlier work from Tarnopolsky et al. showed that men increased muscle glycogen by ~40% after several days of high-carbohydrate eating, while women did not, unless total caloric intake was also incresed.¹⁴ This suggests women may load less effectively when energy intake is low, but load just as well when calorie and CHO intake are adequate. Modern studies rarely control for menstrual cycle variability, which could meaningfully affect results.¹⁵, ¹⁶, ¹⁷, ¹⁸
*See cited research for additional information on CHO loading in female athletes
A recent narrative review in Nutrients summarizes the evolution of CHO-loading strategies and the shift from classic to more modern protocols.¹⁹
One interesting point raised is that factors such as anxiety and environmental temperature may influence glycogen storage. This highlights how much context matters when deciding what to prioritize as an athlete.
How Much and How Long?
CHO needs are typically expressed in grams per kilogram of body weight, and recommended loading duration is given in hours or days.
This is where I found unexpected inconsistency, both from conversations with athletes and coaches, and from my readings. Some coaches recommended a three-day load above 8 g/kg for a half marathon; others said loading wasn’t necessary for that distance. Some athletes suggested starting at 7-12 g/kg a full week before; others claimed that one carb-heavy dinner was enough.
The discrepancy shows up in the research as well. Much of the carb-loading literature is quite old yet continues to dominate public discussions. Even Precision Fuel & Hydration, a company built around endurance fueling, cites research from 1969 as their most recent source on this topic.²⁰
1960s Research and “Supercompensation”
The early studies remain foundational, but their methods were crude. Athletes underwent a three-day depletion phase, which included very low carbohydrate intake plus heavy training, followed by three days of very high CHO intake to achieve “supercompensation,” or glycogen levels above baseline.²¹, ²²
More recent work, including a 2025 meta-analysis, supports the idea that supercompensation is possible. But the magnitude is highly individual, and it’s unclear whether supercompensation enhances performance or simply increases muscle water content and size, which matters for hypertrophy-centric sports but not necessarily for running. Running may benefit least, as supercompensation magnitudes appear smaller than in cycling.²³
Another key issue with older research is that athletes began loading in a depleted state. They weren’t just filling glycogen stores; they were refilling what had been emptied through deliberate depletion. This likely explains why they needed three days of loading to see substantial increases. More recent work shows you can achieve supercompensation without a depletion phase if CHO intake is high enough.²⁴
More Current Views
More modern guidelines emphasize 90 minutes as the key threshold. In the late 1990s, research showed that elevating muscle glycogen above normal resting levels has little effect on events lasting 60–90 minutes because glycogen is not fully depleted.²⁵ Once duration exceeds ~90 minutes, elevated glycogen appears beneficial.
The International Association of Athletics Federations (IAAF) 2019 consensus statement on athlete nutrition recommends: ²⁶
Half marathon: 7–12 g/kg CHO for 1 day
Marathon: 10–12 g/kg for 1.5–2 days
It's unclear why the loading duration differs between the two distances. If the goal is to “fill” stores, one would assume the same strategy should apply unless the intent is supercompensation. Interestingly, the same author later states that for any event exceeding 90 minutes, glycogen loading should begin 36–48 hours prior, with 10–12 g/kg/day, without a clear explanation for this difference.²⁷
Another important nuance: although guidelines categorize strategies by race distance, they should really be applied to the individual’s expected duration and intensity. A new runner might spend 120+ minutes in a half marathon and fully deplete glycogen. A highly trained runner might finish in 75 minutes and never come close to depleting stores.
One of my favourite papers by Burke et al., 2011 provides an excellent overview.²⁸ The authors note that in the absence of muscle damage, glycogen stores can be restored within 24 hours of reduced training and adequate fueling. Events lasting 90 minutes or more may benefit from higher stores, but extremely high intakes may not be practical.
A Note on GI Tolerance
GI tolerance is a major limiter. If an athlete cannot tolerate very high CHO intakes over 1–2 days, spreading the intake over more days may be necessary, even if this lowers the likelihood of achieving true “supercompensation.”
Practical Takeaway for Carb Loading
This area of research still has gaps, and I think we’re far from having a unified, evidence-based protocol. But Burke and colleagues (2011) provide what I see as the most practical and realistic summary of the evidence to date. My analysis of the data leads to the take-home points below:
Race duration < 90 min
Rested and tapered glycogen is usually enough
Carb loading rarely improves performance
7-12g/kg/day for 1 day may be beneficial to guarantee glycogen replenishment
Race duration 90–120 min
Start fully topped up (single-day carb load with sufficient rest is enough)
7-12g/kg/day for 1-2 days will likely be beneficial to guarantee glycogen replenishment
Benefits are inconsistent but physiologically plausible especially at high intensities
Race duration 2–3 hours
Classic carb loading may have a meaningful benefit (including depletion)
10-12g/kg/day for 1-2 days will likely be beneficial and may lead to supercompensation
Relying on stored glycogen is insufficient and In-race fueling becomes essential to hold performance
Race duration 3+ hours
The goal is maximizing total carbohydrate availability, not just filling stores
Classic carb loading may have a meaningful benefit (including depletion)
10-12g/kg/day for 1-2 days will likely be beneficial and may lead to supercompensation
Fueling strategy during the race likely determines performance more than glycogen availability
My Carb Loading Experience
For my own carbohydrate loading trial, I kept things simple and focused on the fundamentals. I followed a 24-hour protocol at roughly 8 g per kilogram, paired with a lower fiber, lower fat, moderate protein intake to keep digestion easy and help me reach the target. I emphasized simple, low GI carbohydrate sources that I know sit well for me so I could get the volume in without feeling weighed down. I was also intentional with hydration and sodium intake, since carbohydrate storage depends heavily on water and electrolyte balance. This helped support glycogen storage without leaving me feeling overly bloated.
Why a single day load?
I opted for a single day load because, based on more current research, extending the process over several days didn’t seem necessary for restoring my glycogen stores. I was already well recovered from my taper and had been eating sufficient carbohydrates leading in, so there was no need to “catch up” or refill from a depleted state. A focused 24-hour load was enough to top off what I already had.
I also wanted to test my gastrointestinal tolerance for taking in that amount of carbohydrate within one day. This was an important trial run for my marathon preparation, where I will likely need to sustain a high carbohydrate intake for two to three days if I aim for some level of supercompensation. Understanding how my body responds to that density of intake now gives me a clearer picture of how to structure the longer loading period later on.
Areas for Improvement
There are a few refinements I’ll make next time.
First, I would include a short shakeout run during the loading period. Light exercise increases GLUT4 translocation, which improves glucose uptake into muscle and can support glycogen synthesis.
For future races, especially my full marathon where supercompensation may matter more, I am considering a backloaded approach. This would involve one higher carbohydrate day two or three days out, followed by one or two moderate carbohydrate days.
The goal is to keep glycogen stores elevated while giving my gastrointestinal system time to settle before the race. This may offer the benefits of high intake without carrying the GI burden right into race morning. Although this would likely impact supercompensation.
Conclusion
Peaking effectively in endurance sport requires a personalized approach that combines tapering training volume while maintaining intensity and eating sufficient carbohydrates to replenish glycogen stores. This blog represents a personal experiment and evidence-based thought-process. Understanding your body, testing strategies, and applying science can make a significant difference in performance outcomes. More importantly, it can help you to feel your best at competition, keeping the process enjoyable.
Thanks for reading and following along. If there is anything to take from this it’s training hard is important, pushing your boundaries is fun and can be a learning experience, but planning recovery and fueling properly is what allows you to show up at your best.
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