RESEARCH: Studies from 28 Apr to 4 May 25
Sharing research and insights from coaches, scientists and athletes to help us improve endurance performance.
This week’s quick summary:
Cross-education of lower limb muscle strength following resistance exercise
Comparative efficacy of concurrent training types on lower limb strength
Effect of acute caffeine intake on fat oxidation rate
Nutritional strategies to improve post-exercise recovery
Mechanistic influence of the torque cadence relationship on power output
STRENGTH: Cross-education of lower limb muscle strength following resistance exercise training in males and females
Cross-education refers to training one limb and gaining strength in the opposite, untrained limb, primarily through neural rather than muscular adaptations. Previous research has shown that cross-education can improve upper limb strength, but evidence for its effect on lower limb strength was less consistent. In this review, the authors aimed to "evaluate the efficacy of cross-education (vs. a control group) via resistance exercise training for improving muscle strength in the untrained lower limb”.
REVIEW DETAILS
29 studies involving healthy males and females were included in the systematic review and meta-analysis.
The intervention involved unilateral resistance exercise training (RET) programmes using concentric, eccentric, or mixed contraction modes.
Study durations varied but typically ranged from several weeks to a few months.
Strength outcomes were measured through changes in one-repetition maximum (1-RM), maximum voluntary contraction (MVC), and concentric, eccentric, and isometric peak torque.
Cross-education significantly improved all measured strength outcomes compared to controls, with eccentric training particularly effective for enhancing isometric strength.
PRACTICAL TAKEAWAY
This review showed that unilateral resistance exercise training can meaningfully increase muscle strength in the untrained lower limb. Eccentric-focused exercises were especially effective for boosting isometric strength. My recommendation for injured athletes is to use this cross-education effect as a rehabilitation strategy by continuing to train, where possible, using their uninjured limb. This is mostly likely possible for strength training, but it can also be used on a stationary trainer or using one-armed drills in swimming.
RELATED RESEARCH
STRENGTH: Comparative efficacy of concurrent training types on lower limb strength and muscular hypertrophy
Concurrent training, combining resistance and endurance exercises, can improve overall fitness but may compromise muscle growth and strength gains. Previous research suggests endurance type and intensity influence this interference effect, yet consensus is lacking. In this review, the authors sought to “compare, through quantitative analysis, the effectiveness of different endurance training types on increasing lower limb strength and muscle cross-sectional area (MCSA) in concurrent training”.
REVIEW DETAILS
The meta-analysis included 40 studies with a combined total of 841 participants.
All studies used concurrent training interventions pairing endurance and resistance training.
Intervention duration and training modalities varied, but all reported changes in lower limb strength and/or MCSA.
Concurrent high-intensity interval running and resistance training showed better effects on MCSA than resistance training alone, while other combinations did not.
Resistance training alone remained superior for maximal strength, though high-intensity interval training combined with resistance training lessened the performance drop and even improved explosive strength.
PRACTICAL TAKEAWAY
This review showed that pairing high-intensity interval running with resistance training preserves or enhances lower limb muscle size and strength better than other endurance modalities. My recommendation for athletes combining strength and endurance training with a focus on strength, is that they should prioritise high-intensity interval running to mitigate interference effects. This will require coordinating the strength and endurance training phases carefully. For example, focusing on strength with multiple weekly sessions in the winter training blocks and performing shorter intervals in the same block rather than building an endurance base.
RELATED RESEARCH
SUPPLEMENT: Effect of acute caffeine intake on fat oxidation rate during fed-state exercise
Caffeine intake before exercise is known to enhance fat oxidation, particularly in fasted conditions. However, this effect may be diminished when exercise is performed after a meal, due to interactions between caffeine and post-meal glucose and insulin dynamics. In this review, the authors aimed to “analyse investigations on the effect of acute caffeine intake on the rate of fat oxidation during submaximal aerobic exercise performed in the fed state”.
REVIEW DETAILS
The review included 18 randomised, placebo-controlled crossover trials with 228 participants (185 males, 43 females) published between 1982 and 2021.
All studies evaluated submaximal aerobic exercise conducted within 5h of a meal and compared caffeine doses (~3–9mg/kg) with a placebo.
Overall, caffeine increased fat oxidation during fed-state exercise, with a moderate effect size across 20 placebo-caffeine comparisons.
Doses <6mg/kg increased fat oxidation, whereas doses ≥6mg/kg showed no effect.
The effect was significant in caffeine-naïve and active untrained individuals, but not in regular caffeine users or aerobically trained participants.
PRACTICAL TAKEAWAY
This review showed that consuming <6mg/kg of caffeine before fed-state submaximal aerobic exercise can enhance fat oxidation in caffeine-naïve and recreationally active individuals. However, trained athletes or habitual caffeine users may not experience this benefit. My recommendations for athletes aiming to use caffeine to support fat oxidation is to manage their daily coffee consumption to limit caffeine so they only use it in support of key training sessions.
RELATED RESEARCH
NUTRITION: Nutritional strategies to improve post-exercise recovery and subsequent exercise performance
Post-exercise recovery plays a critical role in performance outcomes, particularly when recovery time is limited. Existing research highlights how nutrition can enhance recovery by promoting glycogen replenishment, muscle repair, and physiological adaptation. In this review, the authors aimed to “examine the impact of nutritional strategies commonly used for enhancing recovery and subsequent exercise performance”.
REVIEW DETAILS
The review summarised existing evidence rather than conducting an experimental intervention, drawing from current literature on recovery nutrition in trained athletes.
Nutritional strategies analysed included carbohydrate, protein, fat, and micronutrient intake, as well as hydration methods relevant to short recovery periods.
Carbohydrate intake immediately post-exercise was emphasised for rapid glycogen restoration, particularly when high amounts are not feasible, with benefits enhanced by protein co-ingestion.
Protein type and dose were identified as critical for muscle repair and nitrogen balance, with evidence favouring fast-digesting sources in appropriate quantities.
Co-ingestion of creatine, caffeine, and specific micronutrients like omega-3s and sodium bicarbonate was associated with reduced muscle damage and improved performance markers.
PRACTICAL TAKEAWAY
This review showed that recovery nutrition should be tailored to the demands of short turnaround periods between training or competitions. Emphasis should be placed on timely carbohydrate and protein intake, with co-ingestion strategies and hydration playing a supporting role. My recommendation for athletes is to create a repeatable post-race or post-training routine that involves hydrating and eating enough carbohydrates (~50g) and enough protein (~30g) to start their recovery immediately. This could be in the form of a hydration drink, a protein bar and carbohydrate bar, or a recovery drink that includes everything.
RELATED RESEARCH
PHYSIOLOGY: Mechanistic influence of the torque cadence relationship on power output during exhaustive all-out field tests in professional cyclists
The relationship between torque, cadence, and power output has been widely examined in cycling research, mostly in laboratory environments. However, field-based assessments may better reflect real-world performance in elite cyclists. In this study, the authors set out to “examine the mechanistic influence of the torque-cadence relationship on power output under fresh and fatigued conditions in professional cyclists".
STUDY DETAILS
17 elite male cyclists (mean age 24.1years, body mass 66.0kg, critical power 5.5W.kg⁻¹) were tested during a pre-season training camp.
Cyclists performed sprint, torque, and critical power tests under both fresh and accumulated work conditions using multiple durations (15s, 3min, 12min).
All-out tests were conducted outdoors in stable environmental conditions (15–20°C), using varied gear ratios to elicit a wide range of torque and cadence outputs.
After accumulated work, power output, torque, and cadence decreased across all test durations.
Tmax (from sprints) was strongly associated with torque intercepts for critical power, and Cmax was negatively correlated with cadences during fatigued tests, indicating consistent declines in cadence with fatigue.
PRACTICAL TAKEAWAY
This study showed that accumulated work significantly lowers both cadence and power output in elite cyclists. This is a useful marker of durability and is something that could be incorporated into field testing or used during training. My recommendation for athletes is to start monitoring changes in torque and cadence and to capture that data for their own analysis. Being aware of the usefulness of these metrics and learning how they change under different conditions can help inform future training.
RELATED RESEARCH
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 (625 studies and practical takeaways). Last week, the newsletter covered studies on the following topics:
Common questions and misconceptions about creatine supplementation
Elite collegiate swimmers do not meet sport nutrition recommendations
Post-exercise cooling lowers skeletal muscle microvascular perfusion
Influence of "live high-train low" on hemoglobin mass
Neuromuscular adaptations to concurrent aerobic and strength training
