Exercise Dose Equalization in High-Intensity Interval Training: A Scoping Review

Current methods for the exercise dose equalization in resistance training drive to markedly different session-induced efforts

BACKGROUND

Effects comparison of resistance exercises may require equalizing the exercise-induced dose, this is currently done by using methods based on total weight lifted or on sets performed until failure. Dose equalization of resistance training sessions by these methods was analyzed in the present study.

METHODS

Twelve trained participants performed five bench-press sessions with a similar relative endpoint determined by the inability to complete a set of 50% of the maximum repetitions number (MNR). Sessions were performed at 50 or 85% of one-repetition maximum (1-RM) with sets until failure or sets prescribing 50% of MNR. The last session was performed with a reduced recovery pause to match the exercise density (total weight lifted/pause duration) of a previous session.

RESULTS

Sessions resulted in different total weight lifted (3158±1592 kg at 85% of 1-RM vs. 5330±1967 at 50%, P<0.001) and number of sets until failure (5.1±1.9 at 85% of 1-RM vs. 2.9±1.1 at 50%, P<0.001). Matching of sessions' density suppressed the differences in the number of sets performed (P=0.50).

CONCLUSIONS

Protocols' equalization based on the total weight lifted is likely to result in exercise volumes close to maximums when performed with heavy loads, whereas equalization based on sets to failure could induce a sets number close to the maximum when performed with light loads. Current methods for protocols equalization rely on gross values of exercise volume without considering maximums, that can result in markedly unbalanced efforts and biased results. Prescribing each exercise volume according to its maximum might optimize the training protocols' equalization.

Effects of thermal interventions on skeletal muscle adaptations and regeneration: perspectives on epigenetics: a narrative review

Recovery methods, such as thermal interventions, have been developed to promote optimal recovery and maximize long-term training adaptations. However, the beneficial effects of these recovery strategies remain a source of controversy. This narrative review aims to provide a detailed understanding of how cold and heat interventions impact long-term training adaptations. Emphasis is placed on skeletal muscle adaptations, particularly the involvement of signaling pathways regulating protein turnover, ribosome and mitochondrial biogenesis, as well as the critical role of satellite cells in promoting myofiber regeneration following atrophy. The current literature suggests that cold interventions can blunt molecular adaptations (e.g., protein synthesis and satellite cell activation) and oxi-inflammatory responses after resistance exercise, resulting in diminished exercise-induced hypertrophy and lower gains in isometric strength during training protocols. Conversely, heat interventions appear promising for mitigating skeletal muscle degradation during immobilization and atrophy. Indeed, heat treatments (e.g., passive interventions such as sauna-bathing or diathermy) can enhance protein turnover and improve the maintenance of muscle mass in atrophic conditions, although their effects on uninjured skeletal muscles in both humans and rodents remain controversial. Nonetheless, heat treatment may serve as an important tool for attenuating atrophy and preserving mitochondrial function in immobilized or injured athletes. Finally, the potential interplay between exercise, thermal interventions and epigenetics is discussed. Future studies must be encouraged to clarify how repeated thermal interventions (heat and cold) affect long-term exercise training adaptations and to determine the optimal modalities (i.e., method of application, temperature, duration, relative humidity, and timing).

How to Equalize High- and Low-Intensity Endurance Exercise Dose

PURPOSE

Without appropriate standardization of exercise doses, comparing high- (HI) and low-intensity (LI) training outcomes might become a matter of speculation. In athletic preparation, proper quantification ensures an optimized stress-to-recovery ratio. This review aims to compare HI and LI doses by estimating theoretically the conversion ratio, 1:x, between HI and LI: How many minutes, x, of LI are equivalent to 1 minute of HI using various quantification methods? A scrutinized analysis on how the dose increases in relation to duration and intensity was also made.

ANALYSIS

An estimation was conducted across 4 categories encompassing 10 different approaches: (1) "arbitrary" methods, (2) physiological and perceptual measurements during exercise, (3) postexercise measurements, and comparison to (4a) acute and (4b) chronic intensity-related maximum dose. The first 2 categories provide the most conservative estimation for the HI:LI ratio (1:1.5-1:10), and the third, slightly higher (1:4-1:11). The category (4a) provides the highest estimation (1:52+) and (4b) suggests 1:10 to 1:20. The exercise dose in the majority of the approaches increase linearly in relation to duration and exponentially in relation to intensity.

CONCLUSIONS

As dose estimations provide divergent evaluations of the HI:LI ratio, the choice of metric will have a large impact on the research designs, results, and interpretations. Therefore, researchers should familiarize themselves with the foundations and weaknesses of their metrics and justify their choice. Last, the linear relationship between duration and exercise dose is in many cases assumed rather than thoroughly tested, and its use should be subjected to closer scrutiny.

Are Activity Wrist-Worn Devices Accurate for Determining Heart Rate during Intense Exercise?

The market for wrist-worn devices is growing at previously unheard-of speeds. A consequence of their fast commercialization is a lack of adequate studies testing their accuracy on varied populations and pursuits. To provide an understanding of wearable sensors for sports medicine, the present study examined heart rate (HR) measurements of four popular wrist-worn devices, the (Fitbit Charge (FB), Apple Watch (AW), Tomtom runner Cardio (TT), and Samsung G2 (G2)), and compared them with gold standard measurements derived by continuous electrocardiogram examination (ECG). Eight athletes participated in a comparative study undergoing maximal stress testing on a cycle ergometer or a treadmill. We analyzed 1,286 simultaneous HR data pairs between the tested devices and the ECG. The four devices were reasonably accurate at the lowest activity level. However, at higher levels of exercise intensity the FB and G2 tended to underestimate HR values during intense physical effort, while the TT and AW devices were fairly reliable. Our results suggest that HR estimations should be considered cautiously at specific intensities. Indeed, an effective intervention is required to register accurate HR readings at high-intensity levels (above 150 bpm). It is important to consider that even though none of these devices are certified or sold as medical or safety devices, researchers must nonetheless evaluate wrist-worn wearable technology in order to fully understand how HR affects psychological and physical health, especially under conditions of more intense exercise.

Editorial: New Training Strategies and Evaluation Methods for Improving Health and Physical Performance

Physical activity is among the most effective methods for improving health, body composition, and physical function, and its practice is suitable for every population [...].