RESEARCH: Studies from 20 to 26 Jan 25
Sharing research and insights from coaches, scientists and athletes to help us improve endurance performance.
This week’s quick summary:
Iron deficiency, supplementation, and performance in female athletes
Track-and-field coaches’ perspectives of their planning processes
Is there any evidence for embedding carbon plate in trail running shoes?
Influence of interval training frequency on time-trial performance
Aerobic exercise does not affect anabolic signalling from resistance exercise
SUPPLEMENT: Iron deficiency, supplementation, and sports performance in female athletes
Iron deficiency impacts up to 60% of female athletes which can negatively affect sports performance. In this study, the authors aimed to “investigate how iron deficiency influences performance in high-level female athletes and the benefits of iron supplementation [to] help optimise training and competition outcomes for athletes”.
STUDY DETAILS
669 iron-deficient female athletes aged 13–47 years from 16 sports were included, with VO2 Max >45mL/kg/min or training >5h/week.
Athletes received 16–100mg/day of elemental iron for 36–126 days or 100mg bi-daily over 8–10 days.
Endurance performance decreased by 3%–4% in iron-deficient athletes but improved by 2%–20% with supplementation. Maximal aerobic capacity increased by 6%–15%.
Serum ferritin levels (<40µg/L), endurance metrics, maximal aerobic capacity, and anaerobic power were assessed.
Anaerobic power changes ranged from –5% to +9%, and isokinetic strength showed variability (–23% to +4%). Smaller studies (<20 participants) limited statistical power.
PRACTICAL TAKEAWAY
The results of this study showed that iron supplementation improves endurance and aerobic capacity in iron-deficient female athletes. My recommendation for athletes (and female athletes in particular) is to have an annual blood test to check their iron levels. Then they can follow the guidance from their doctor if an intervention is necessary. Athletes who are planning to go to altitude, or are worried about iron deficiency, and who don’t want to do a blood test, can try supplementing for two to four weeks with 100mg of iron taken every other day.
RELATED RESEARCH
COACHING: Making the invisible, visible: An exploration of track-and-field coaches’ perspectives of their planning processes
Traditional coaching models often suggest that coaches develop periodised plans based solely on physiological principles. In this study, the authors set out “to uncover the information coaches consider and how they actually approach the task of planning”.
STUDY DETAILS
Participants included 28 experienced high-performance track-and-field coaches from England (1 female, 27 male), specialising in throwing (10) and endurance running (18).
Each coach participated in up to 3 semistructured interviews over a full athletics season, totalling 68 hours of data.
Interviews focused on coaches' understanding of their planning practices, aiming to bridge the gap between academic research and real-world application.
Findings revealed that while coaches employed periodisation principles, their planning extended beyond physical training to encompass athletes' psychological, personal, and social development.
Coaches viewed successful athletic performance holistically, indicating that planning is multifaceted and not limited to physiological aspects.
PRACTICAL TAKEAWAY
The outcomes of this study showed that coaches take a holistic approach to training their athletes that extends beyond just applying theoretical frameworks. My recommendation for coaches is to start their planning process with an “ideal” training plan in mind, then to adjust that to the athletes they are training and how the athletes adapt to that training. The plan is more of a map with a destination rather than a definite, fixed route that must be taken. For athletes, my recommendation is to communicate frequently with your coach to ensure they have all the information needed to help change and adapt the training plan.
RELATED RESEARCH
EQUIPMENT: Effect of increased bending stiffness on running economy and joint biomechanics in uphill running and running on unstable terrain: is there any evidence for embedding carbon plate in trail running footwear?
The advent of carbon-plated running shoes has revolutionised road running, but their efficacy on trails remains uncertain. In this study, the authors aimed to “evaluate the impact of increased longitudinal bending stiffness (LBS) in carbon-plated trail shoes on uphill running to see if they provide physiological or biomechanical advantages in technical trail running conditions”.
STUDY DETAILS
10 amateur trail runners participated in the study, testing footwear with and without carbon plates.
Running conditions included treadmill assessments at speeds of 11.6±1.2km/h (level) and 7.8±0.6km/h (uphill), with 3D kinematics and kinetics measured on unstable terrain.
Metabolic power showed no differences on level terrain but increased by 2% during uphill running with the plated footwear.
Joint biomechanics (e.g. frontal peak angles, ranges of motion) and plantar feedback did not differ between shoe conditions.
Bayesian statistical parametric mapping revealed no biomechanical advantages for the plated footwear during technical trail running.
PRACTICAL TAKEAWAY
This study showed that carbon-plated trail shoes may not enhance performance for uphill or technical terrain running due to increased metabolic power requirements. My recommendation is that trail runners should prioritise footwear suited to the terrain of their race. For flatter, less technical trails, carbon-plated shoes might still provide an advantage. For more technical trails, it may be best to prioritise comfortable, light shoes that provide sufficient traction and stability over carbon-plated shoes.
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TRAINING: Influence of interval training frequency on time-trial performance in elite endurance athletes
Optimising training frequency is key for endurance athletes aiming to enhance performance. While higher training frequency is often associated with greater fitness gains, recovery may be compromised. In this study, the authors investigated “whether two longer interval sessions per week could out-perform four shorter ones in promoting physiological adaptations and performance”.
STUDY DETAILS
The study involved 15 elite cross-country skiers and biathletes (22y; VO2 Max 67.8-70.7mL/kg/min), randomly assigned to either a low-frequency (LF) or high-frequency (HF) training group.
The LF group performed two longer interval sessions per week, while the HF group completed four shorter ones. All sessions were conducted at ~85% of maximum heart rate, with matched weekly training volume.
Pre- and post-intervention assessments included an 8km rollerski time trial, VO2 Max testing, and submaximal exercise tests.
Only the LF group showed improved time-trial performance, anaerobic threshold utilisation, and exercise economy.
No changes in VO2 Max were observed in either group.
PRACTICAL TAKEAWAY
The results suggest that endurance athletes may benefit more from fewer, longer interval training sessions rather than shorter, frequent ones. This approach promotes endurance adaptations and allows sufficient recovery, enhancing both performance and exercise efficiency. One important consideration is that the work load was matched for these sessions, however, it may be possible to achieve a slightly higher workload over more frequent and shorter sessions. My recommendation for athletes is to build up to fewer, longer interval sessions. A starting point might be four, short intervals, then progressing to three longer sessions, and finally doing two, long interval sessions per week.
RELATED RESEARCH
STRENGTH: Aerobic exercise intensity does not affect the anabolic signalling following resistance exercise in endurance athletes
Concurrent training combines resistance and endurance exercise, however, some athletes have concerns about potential molecular interference, where endurance exercise may suppress anabolic signalling pathways, such as mTOR, linked to muscle growth. In this study, the authors “explored whether the intensity of endurance exercise impacts the activation of key signalling protein responses to concurrent training”.
STUDY DETAILS
8 male cyclists participated in a cross-over study involving three conditions: resistance exercise (RES), RES plus moderate-intensity cycling (RES+MIC), and RES plus high-intensity interval cycling (RES+HIIC).
The resistance protocol included 6×8 squats at 80% 1RM, while the cycling protocols lasted 40 minutes, with MIC at 65% VO2 Peak and HIIC alternating between 85% and 45% VO2 Peak.
Muscle biopsies were collected at rest and three hours post-RES to assess phosphorylation of proteins linked to mTOR and AMPK pathways.
mTOR activation was greater in the RES+MIC condition than in RES, suggesting enhanced anabolic signalling.
AMPK activation was also higher in RES+MIC compared to both RES and RES+HIIC, indicating improved endurance signalling without interference effects.
PRACTICAL TAKEAWAY
The results of this study showed that resistance training followed immediately by cycling was most effective when the cycling was performed at a moderate rather than a high intensity. However, the differences were relatively small leading the authors to conclude “that endurance athletes need not be concerned with the intensity of their endurance session (moderate vs. high intensity) affecting their strength adaptation, when the two exercise modes are performed in close proximity to one another.” My recommendation for athletes who want to perform concurrent sessions is to use these sessions when they are aiming to maintain fitness or add volume and to keep both the strength and endurance training moderate. For key sessions where progress in a specific physiological adaptation is the goal, I would still recommend doing these as individual sessions rather than as part of a concurrent session, but this study suggests that may not be as important as previously considered.
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Quick summary from last week’s paid newsletter
Paid subscribers receive a newsletter every week and have full access to all newsletters listed in the archives (555 studies and practical takeaways). Last week, the newsletter covered studies on the following topics:
Delayed-onset muscle soreness does not reflect muscle damage
Cardiovascular and muscular plasticity in an endurance athlete
Nutritional interventions with variable carbohydrates and glycaemic indices
Intake of a ketone ester drink during recovery from exercise
Towards precision sports nutrition for endurance athletes
This is great! I especially relate to the iron deficiency part. I was diagnosed with iron deficiency anemia in 2019. I had a ferritin level of 4. I needed two iron infusions in the hospital. Now, years later, I take ferrous fumarate every other day and my levels stay stable, even with Ironman training. I wrote a blog post about it on my website if you want to check it out! It's called (IRONman: A Triathlete with Iron Deficiency Anemia,) because my husband can't resist a good pun. :) https://bybrittanyvermeer.com/2024/03/ironman-triathlete-with-iron-deficiency-anemia/