This study highlights the potential for protein supplementation to enhance the effectiveness of concurrent training, which combines aerobic and resistance exercises within the same session. Concurrent training is increasingly recognized as a time-efficient and effective strategy for improving both cardiorespiratory fitness and muscle strength, which makes it particularly appealing for people with limited time for exercise.

Despite long-standing concerns about the interference effect,^[1] in which adaptations in strength and endurance may counteract each other, this study and others suggest that these effects are minimal, especially in untrained people.^[2]^[3] Although concurrent training does impose unique physiological demands, such as glycogen depletion from aerobic activity that can potentially affect resistance performance, the observed benefits in both VO2max and strength suggest that these challenges can be managed effectively, especially with nutritional strategies like protein supplementation.^[4] These findings support the growing consensus that concurrent training is a practical and effective approach for improving overall fitness.

This is particularly true when time constraints are a critical factor. One of the major advantages of concurrent training is its ability to integrate both fitness modalities into a single, shorter session, resulting in improved adherence compared to separate endurance and resistance training programs. Training separately for each outcome often requires more time and planning, which can lower adherence rates. By incorporating both modalities, concurrent training maximizes health benefits and is practical and accessible for people with busy schedules.

The study also provides key insights into the role of protein supplementation in enhancing strength gains during concurrent training. The protein group showed greater improvements in 1RM strength across all muscle groups, particularly in the legs, where the placebo group demonstrated only small gains. This aligns with evidence that protein consumption promotes muscle protein synthesis, aids recovery, and reduces muscle breakdown, all of which are critical for strength adaptation.^[5]^[6]

Because the participants in this study consumed their protein after their workout, the relevance of protein timing warrants further consideration. Although the so-called postexercise “anabolic window” is likely less relevant and much wider than previously thought,^[7]^[8] consuming protein immediately after a workout remains a practical strategy. A postworkout intake routine likely reinforces adherence, and, for people who like the supplement's taste, it can be a satisfying reward after exercise. Additionally, given the transient anabolic effects of a typical protein-rich meal, consuming protein at least 3 to 4 times per day, approximately 3 to 5 hours apart, may be ideal.^[9] However, it’s also worth noting that other timing strategies, such as unevenly distributing protein intake throughout the day, can still support strength and fitness gains.

Interestingly, the observed strength gains did not translate to detectable changes in muscle mass within the covered study’s timeframe. This apparent lack of hypertrophy could be attributed to several factors, including the short duration of the intervention (8 weeks), the low training volume, and the untrained nature of the participants, which meant that they may have exhibited neural adaptations (improved motor unit recruitment and coordination) rather than hypertrophy as the primary driver of strength gains in the initial phases of training. As such, muscle mass improvements often require longer interventions or higher training volumes to become apparent.^[10] It’s also worth noting that the method used to measure muscle mass, bioelectrical impedance, is not considered the most reliable method for measuring body composition.^[11]

Beyond muscle mass and strength, concurrent training may have distinct effects on performance outcomes related to power and agility. Although concurrent training is highly effective for improving general fitness, the demands of endurance training can interfere more noticeably with activities that rely heavily on rapid power output or agility.^[3] For example, a powerlifter might not experience a significant drawback from incorporating moderate aerobic exercise, such as jogging, into their routine. However, athletes whose success depends on peak explosiveness (such as sprinters, throwers, or high jumpers) could see a reduction in their capacity for rapid, high-intensity movements due to the physiological demands of concurrent training. Similarly, in team sports, intensive conditioning may slightly diminish the explosiveness and agility required for quick changes of direction or bursts of speed. For people whose primary goal is to maximize power-based performance, it may be wise to minimize endurance training as much as possible while still maintaining adequate conditioning to meet sport-specific needs.

In summary, these findings underline the practicality and effectiveness of concurrent training as a balanced approach to fitness. Protein supplementation can amplify strength gains, which makes it a useful strategy for people seeking efficient, comprehensive fitness improvements. For untrained people or people with busy schedules, concurrent training combined with simple nutritional strategies like whey protein supplementation represents an effective and time-efficient tool for achieving meaningful health and fitness outcomes.

Does protein supplementation enhance the effects of exercise? Original paper