Inside Andrew Musgrave's Pre-Olympic Training Block

There’s now just fourth months until the start of the 2026 Winter Olympics, and many endurance-based athletes will soon be transitioning from their “base building” training and into a phase that more closely reflects race specificity. One of those athletes is Scottish-born and Norway-based cross country skier Andrew Musgrave, who will be representing Great Britain at Milan-Cortina in February. Cross country skiing, for reasons that will be discussed in this article, is the best sport for producing aerobic machines with seven of the top fifteen publicly available VO2Max recordings coming from cross country skiers. This, combined with Musgrave’s sensible and effective training principles, provides a strong enough rationale for an article analysing his final “base building” phase before the Olympics, in the hope of discovering lessons that are applicable to all endurance athletes.

Andrew Musgrave. Image from In the Snow.

Training Monitoring

Before analysing an athlete’s training, it’s important to ensure that the training is effective in improving endurance performance. Between the end of May and mid-October, Musgrave completed numerous maximal and submaximal tests to measure maximal oxygen uptake (VO2Max, the highest rate in which in the body can use oxygen for exercise), the lactate threshold (LT2, the point in which exercise becomes metabolically unstable which is indicated by lactate production exceeding lactate clearance), movement economy (O2 cost, the amount of oxygen needed to sustain a given intensity) and effort perception (RPE, which is measured on a scale of 6-20, with 6 being rest and 20 being maximal effort).

There is no single metric that predicts endurance performance, especially at the Olympic level, but VO2Max is a good indicator of an athlete’s aerobic “ceiling” and a good general indicator of aerobic performance as it encompasses pulmonary, cardiovascular and metabolic functions. At the beginning of this training cycle, Musgrave’s VO2Max was at 75.4ml/kg/min which increased 5.2ml/kg/min up to 81.6ml/kg/min when he re-tested seven weeks later. He tested again six weeks later, but only scored 76.6ml/kg/min, a 5ml/kg/min decrease from previous testing before achieving 84.5ml/kg/min on the 24th of October, which was a lifetime best and, for reference, is just 0.1ml/kg/min lower than what was achieved by Chris Froome in 2015.

An 11% increase in VO2Max across four and a half months for an Olympic level endurance athlete is extremely impressive. This shows that training has been effective in inducing adaptations that should improve endurance performance, but it’s worth noting that Musgrave’s first test likely occurred following a post-season break and that the numbers are not a true reflection of his true fitness. Once he began training consistently, it’s likely that he re-found a level of fitness that’s more reflective of his true shape. It’s also worth noting that the 5ml/kg/min decrease on the third test was unlikely to be fitness related and can be attributed to a lack of motivation to achieve such a high effort level. What is not often discussed around VO2max protocols is the importance of being in the correct psychological state to achieve values that represent the athlete’s physiological capacities. Additionally, motivation is not a case of “how badly do you want it?” but is a computation of a vast number of internal datapoints, developed from before the palaeolithic era, that determines how necessary an activity is for our survival. Motivation can be suppressed in periods of caloric deficit or sleep deprivation, where expending more energy (which in the case of a VO2max test, is a lot of energy) may not be beneficial to sustaining life. VO2Max tests are extremely intense (as is shown in the above video) and the reward of completing the task is not sufficient for the athlete to always be motivated enough to achieve accurate results.

Despite the lack of motivation during this test, Musgrave’s oxygen uptake was still increasing when he reached “exhaustion” which suggests he didn’t reach close to his physiological ceiling. Additionally, his blood lactate concentration during the submaximal test was 0.1-0.2mmol/L lower than the previous test, which indicates that his fitness was still improving despite reaching “exhaustion” much earlier than the previous test.

I think it’s fair to assume that, despite the decrease in VO2Max on the third test, Musgrave’s general fitness did continuously improve across the summer and into autumn which has resulted in an aerobic capacity that would challenge most endurance athletes in history. The next section will analyse the training principles that likely contributed to this improvement.

Large Volumes of Low Intensity

Musgrave’s summer was built on a foundation of huge training volumes at a low intensity. In terms of single sessions, the vast majority exceeded 90 minutes in length while training weeks very often exceeded 15 hours of endurance training (alongside multiple hours of strength training). The primary physiological adaptations tied to large training volumes at a low intensity are relating to mitochondrial biogenesis, proliferation and angiogenesis (simply, the forming of more mitochondria or capillaries, which are vital for oxygen utilisation and the delivery of oxygen to the cells).

The formation of new mitochondria isn’t limited to a specific training intensity, though. Research has found low intensity, high intensity and sprint interval training to be effective in inducing mitochondrial biogenesis. This is supported by a systematic review by Mølmen, Almquist and Skattebo (2025), who found all three training intensities to be effective but at different timescales. They found high intensity and sprint interval training to be effective in inducing fast changes in the mitochondria before a potential plateau, while low intensity training was slower in achieving these adaptations, but is more likely to allow for continued adaptation over a macrocycle and beyond.

Results from Mølmen, Almquist and Skattebo (2025).

It’s also possible that low intensity training can provide a strong cardiovascular stimulus, especially in relation to stroke volume (how much blood the heart can pump per heartbeat). Research on this topic is inconclusive, but exists a number of cases suggesting that stroke volume plateaus and even declines as heart rate increases (Vieira et al. 2016) which points towards the possibility of the left ventricle being maximally stressed even at low intensities. However, this research also found that well-trained humans were less likely to notice a plateau/decline in stroke volume with increases in exercise intensity, meaning this may not apply to someone of Musgrave’s standard, but the possibility is worth noting as low intensity exercise is often associated exclusively with peripheral adaptations, not central ones.

It’s important to note that these adaptations are not limited to sport specific movement patterns. Throughout the summer, Musgrave also completed fairly large volumes of running to support his aerobic development while ensuring training doesn’t become too monotonous. Outside of ground reaction forces, his run training tended to induce similar physiological stresses as skiing, with the majority of his runs being between 2-3 hours at a very low intensity (it’s worth noting that more recently his run workouts have switched to an uphill treadmill with an added heat stress, the goal of which is to increase blood plasma volume in the hope of stimulating an increase in haemoglobin mass, which would enhance oxygen carrying ability). If peripheral (and potentially central) adaptations being stimulated through a range of intensities, running would very likely provide a very similar physiological response to skiing. In addition to this, a change in endurance modalities allows for training to remain interesting in the hope of preserving motivation, which is vital to maintain for endurance athletes completing such large volumes of work every day. Double olympic gold medalist Nils van der Poel (2022) consistently cited motivation as the primary obstacle to sustaining large training volumes during the “aerobic phase” (or base phase) and made a conscious effort to preserve his enthusiasm for training so that he could accumulate more volume. The problem of motivation (to consistently sustain 15+ hour training weeks) is likely shared amongst world-class endurance athletes who train huge weekly volumes, and it seems that running might have provided a healthy outlet for Musgrave to accumulate more training hours while limiting the risk of psychological burnout.

In conclusion, despite these adaptations (primarily mitochondrial/capillary based) occurring at almost all intensities, the athlete who views them as a function of volume and frequency rather than intensity is more likely to achieve these adaptations in both a safe and sustainable manner.

Extensive Spiced With Intensive

Many of Musgrave’s workouts weren’t exclusively low intensity - many included very short repetitions at a high intensity. These repetitions ranged from 10-30 seconds and were often completed in a relatively large volume compared to other endurance sports like running. A running hill sprint workout is unlikely to exceed 6 x 8 seconds, but Musgrave often completed up to 15 x 10s or 10 x 30s, often alternating between flatter and uphill terrain. In Musgrave’s programme, the 10 second sprints were often completed within a shorter workout of 70-80 minutes alongside some technical work, but 30 second repetitions were often completed in sets of three at the beginning of every hour of a long and low intensity effort. For example: four hours at a low intensity with 3 x 30s sprints at the beginning of every hour, which emulates Jan Olbrecht’s (1997) “extensive spiced with intensive” approach to workout design that he felt was optimal for endurance development.

There’s an important distinction between the metabolic demand of sprint lengths, though. 10 second sprints are likely to be primarily powered by the creatine phosphate system (assuming the rest period between sprints is >2-3 minutes to allow for creatine resynthesis), but anything beyond 10 seconds is going to be increasingly dominated by the anaerobic lactic system. The longer (>10s) sprints are going to metabolically demanding and may impact recovery due to an accumulation of both lactate and hydrogen ions. Within the workout, accumulations of hydrogen ions may impact performance through a reduction in Ca2+ sensitivity of the myofilaments or through an impairment of oxygen delivery to the brain, potentially contributing to central fatigue (Phillips, 2024).

Accumulations of lactate in the bloodstream may negatively influence recovery, too. Lactate is able to cross the blood brain barrier and may play a role in the suppression of ghrelin, a hunger hormone responsible for appetite (McCarthy, Islam and Hazell, 2020) which may impact post-session fuelling from both an energy intake perspective and the replenishment of glycogen stores, potentially impacting the quality of training in the following days (adding weight to the importance of adequate periodisation and training intensity control).

Due to the differing metabolic demands, there are also likely to be slightly different adaptations that are stimulated through this type of training. It’s possible that all types of sprints play a role in the improvement of the mitochondria’s efficiency in utilising oxygen (Granata, Jamnick and Bishop, 2018), with this research suggesting that the improved function of a single mitochondrion may be limited to higher intensity and sprint interval exercise (low intensity training was found to improve mitochondrial function but through increased density rather than the improved function of a single mitochondrion).

Sprint work is likely effective in the recruitment of fast twitch muscle fibres which are very important in cross country skiing (Ørtenblad et al. 2018) to maintain a high velocity at a relatively low cadence (compared to other endurance sports like running or cycling, where athletes may take three strides/cycles more per second than a cross country skier). 20-30 second efforts at maximal intensity will likely produce high concentrations of muscle and blood lactate, potentially stimulating the increase in monocarboxylate transporters 1 and 4 (Longhitano et al. 2022) that play a role in turning lactate into a fuel to further sustain exercise or shuttling it out of the cell to prevent accumulation, which may alter the strong ion difference and indirectly be a factor in hydrogen ion accumulation, which lowers the pH of the cell.

Workout Repetition

At least once a week, Musgrave would complete the same workout: 6 x 8 minutes at either a 3% or 15% gradient on a treadmill. The first 2 minutes of each repetition would be at a constant pace, while the last 6 minutes would be alternating between 40s/60s above and below the pace of the first 2 minutes until the 8 minutes was complete, followed by a ~90-120s recovery period.

In terms of intensity control, Musgrave would only start counting the repetitions when blood lactate exceeded 2mmol/L, and workout intensity would often peak at 16.5-17/20 of perceived effort which likely aligns with the maximal metabolic steady state (the highest intensity in which lactate production is not exceeding its clearance). Musgrave’s heart rate tended to peak at about 85% of maximal heart rate during these sessions, which would also correspond with an intensity around the maximal metabolic steady state.

Image from Fluid Athletics.

The workout itself is a combination of principles utilised by runners who adopt the “double threshold” approach (runners adopting this training method tend to complete continuous repetitions in the morning followed by shorter repetition/recovery periods in the evening), except for Musgrave those principles are mixed into a single session. The first two minutes are likely slightly below the maximum metabolic steady state, while the alternating 40s faster/60s slower is likely designed to allow for a higher power output during the 40s while ensuring blood lactate and general effort perception remains sustainable. This is a Mihaly Igloi inspired idea, who’s workouts included short repetitions (usually 100m-350m) with short recovery periods (40-50 metre walk) in between with the idea of keeping blood lactate in a steady state while giving the athlete an opportunity to accumulate large volumes of race-specific velocities.

Ensuring that blood lactate remains in a steady state may also prevent a prolonged recovery, allowing the athlete to continue to accumulate large training volumes in the following days. A study by Burnley, Vanhatalo and Jones (2012) found that work above the critical torque (which tends to align with the maximal metabolic steady state) produces fatigue four to five times greater than work conducted just 10% below the critical torque. This suggests that there is a “threshold” in which, if bypassed, can produce a steep rise in fatigue and thus recovery. By staying below that threshold, recovery from workouts may be a lot faster, allowing the athlete to accumulate more high quality training in the following days.

As mentioned, Musgrave repeated this workout for months on end (at least once a week but sometimes twice in a day, alternating between classic and double pole styles). Despite zero progression in this workout (in terms of total intense volume), Musgrave made huge adaptations and improvements in both his VO2max (which increased by almost 10ml/kg/min between June and October) and in his actual performance in these workouts (on the first of November his top speed was 23km/h at a perceived effort of 15.5/20, while his top speed peaked at 22km/h at a perceived effort of 16/20 on the eleventh of August). These improvements, despite no changes in the external load of the workout, could add evidence to the concept that progressive overload - in acute settings - is not vital to make improvements. On a macro scale (in terms of monthly/yearly training volume), progressive overload is important in making improvements, but progressing single sessions over a shorter period (like a single macrocycle) might not be necessary to stimulate improvements. With this being said, it’s difficult to extend a workout beyond 6 x 8 minutes at or near the maximal metabolic steady state otherwise the athlete risks losing training quality through a non-metabolic form of fatigue.

Workout Clusters

As is common amongst endurance athletes, especially those based in Scandinavia, Musgrave opted to cluster his intense work together on the same day to form what could be described as a double threshold day. A common pattern would be to include an outdoor workout in the morning (for example: 3 x 20 minutes described as “level 3” which I assume would be zone 3 in a 5 or 7 zone model) with a treadmill workout in the evening (often the classic 6 x 8 minutes at 3/15%, as discussed above). The general idea behind clustering these intense workouts on the same day are to provide more recovery time between harder workouts and to ensure that there’s a clear distinction between a physically easy and physically demanding training day. Musgrave often separated these demanding days with high volume low intensity days. In the day following the double workout example used above, he completed a 3 hour skate with 3 x 30s in the morning with a 90 minute run in the evening, all (aside from the 3 x 30s) were completed at a very low intensity to accumulate 4h 30m of total volume.

It could be argued that completing 30s intense repetitions is adding physiological stress on a day that should be dedicated to easy training, but it’s possible that the 90 seconds of total intensity is overpowered by the 4 hours and 30 minutes of low intensity volume. Even if the 30s repetitions produced high concentrations of blood lactate, if he completed them early enough in the workout then it’s likely that Musgrave finished each training session with concentrations reflecting resting values.

Closing Thoughts

Musgrave’s base phase preparation reinforces key training lessons for all endurance athletes: train a lot (“a lot” is individual), mostly at a low intensity and ensure it is all joyful enough to allow for consistency over many months, which compounds into increased fitness. The specific details of Musgrave’s training may be exclusive to the most aerobically strong athletes in the world, but the principles behind them are applicable to everyone.

The secret is that there are no secrets. Olympians don’t have access to a secret training formula, they simply execute the basics to an incredible standard which allows for uninterrupted training consistency over months and years.

The real challenge is applying these universal principles correctly to suit each individual. Through my coaching work, I help endurance athletes turn theory into practise and ultimately improved performance. For more information, check out my website here.

References

Burnley, M., Vanhatalo, A., & Jones, A. M. (2012). Distinct profiles of neuromuscular fatigue during muscle contractions below and above the critical torque in humans. Journal of applied physiology (Bethesda, Md. : 1985), 113(2), 215–223. https://doi.org/10.1152/japplphysiol.00022.2012

Granata, C., Jamnick, N. A., & Bishop, D. J. (2018). Training-Induced Changes in Mitochondrial Content and Respiratory Function in Human Skeletal Muscle. Sports medicine (Auckland, N.Z.), 48(8), 1809–1828. https://doi.org/10.1007/s40279-018-0936-y

Longhitano, L., Vicario, N., Tibullo, D., Giallongo, C., Broggi, G., Caltabiano, R., Barbagallo,

G. M. V., Altieri, R., Baghini, M., Di Rosa, M., Parenti, R., Giordano, A., Mione, M. C., & Li Volti, G. (2022). Lactate Induces the Expressions of MCT1 and HCAR1 to Promote Tumor

Growth and Progression in Glioblastoma. Frontiers in oncology, 12, 871798. https://doi.org/10.3389/fonc.2022.871798

McCarthy, S. F., Islam, H., & Hazell, T. J. (2020). The emerging role of lactate as a mediator of exercise-induced appetite suppression. American journal of physiology. Endocrinology and metabolism, 319(4), E814–E819. https://doi.org/10.1152/ajpendo.00256.2020

Mølmen, K. S., Almquist, N. W., & Skattebo, Ø. (2025). Effects of Exercise Training on Mitochondrial and Capillary Growth in Human Skeletal Muscle: A Systematic Review and Meta-Regression. Sports medicine (Auckland, N.Z.), 55(1), 115–144. https://doi.org/10.1007/s40279-024-02120-2

Olbrecht, J. (1997) The Science of Winning: Planning, Periodizing and Optimizing Swim Training. F&G Partners.

Ørtenblad, N., Nielsen, J., Boushel, R., Söderlund, K., Saltin, B., & Holmberg, H. C. (2018). The Muscle Fiber Profiles, Mitochondrial Content, and Enzyme Activities of the Exceptionally Well-Trained Arm and Leg Muscles of Elite Cross-Country Skiers. Frontiers in physiology, 9, 1031. https://doi.org/10.3389/fphys.2018.01031

Phillips, S. (2024) ‘What causes (and what does not cause) fatigue’, in Phillips, S., Fatigue in Sport and Exercise, 2nd edn., Abingdon, Oxon: Routledge, pp. 35-227.

van der Poel, N. (2022). How to skate a 10k. Retrieved from https://www.nilsvanderpoel.se/trainingphilosophy

Vieira, S. S., Lemes, B., de T C de Carvalho, P., N de Lima, R., S Bocalini, D., A S Junior, J., Arsa, G., A Casarin, C., L Andrade, E., & J Serra, A. (2016). Does Stroke Volume Increase During an Incremental Exercise? A Systematic Review. The open cardiovascular medicine journal, 10, 57–63. https://doi.org/10.2174/1874192401610010057