The Effect of 30-Second Sprints During Prolonged Exercise on Gross Efficiency, Electromyography, and Pedaling Technique in Elite Cyclists

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.

Effects of Alternating Unilateral vs. Bilateral Resistance Training on Sprint and Endurance Cycling Performance in Trained Endurance Athletes: A 3-Armed, Randomized, Controlled, Pilot Trial

ABSTRACT

Ji, S, Donath, L, and Wahl, P. Effects of alternating unilateral vs. bilateral resistance training on sprint and endurance cycling performance in trained endurance athletes: A 3-armed, randomized, controlled, pilot trial. J Strength Cond Res 36(12): 3280-3289, 2022-Traditional preparatory resistance training for cyclists mainly relies on simultaneous bilateral movement patterns. This lack of movement specificity may impede transfer effects to specific aerobic and anaerobic requirements on the bike. Hence, this study investigated the effects of resistance training in alternating unilateral vs. simultaneous bilateral movement pattern on strength and anaerobic as well as aerobic cycling performance indices. Twenty-four trained triathletes and cyclists (age: 31.1 ± 8.1 years; V̇ o2 max: 57.6 ± 7.1 ml·min -1 ·kg -1 ) were randomly assigned to either an alternating unilateral (AUL), a simultaneous bilateral (BIL) training group or a control group (CON). Ten weeks of resistance training (4 × 4-10 repetition maximum) were completed by both training groups, although CON maintained their usual training regimen without resistance training. Maximal strength was tested during isometric leg extension, leg curl, and leg press in both unilateral and bilateral conditions. To compare the transfer effects of the training groups, determinants of cycling performance and time to exhaustion at 105% of the estimated anaerobic threshold were examined. Maximal leg strength notably increased in both training groups (BIL: ∼28%; AUL: ∼27%; p < 0.01) but not in CON (∼6%; p > 0.54). A significant improvement in cycling time trial performance was also observed in both training groups (AUL: 67%; BIL: 43%; p < 0.05) but not for CON (37%; p = 0.43). Bilateral group exhibited an improved cycling economy at submaximal intensities (∼8%; p < 0.05) but no changes occurred in AUL and CON (∼3%; p > 0.24). While sprint cycling performance decreased in CON (peak power: -6%; acceleration index: -15%; p < 0.05), improvement in favor of AUL was observed for acceleration abilities during maximal sprinting (20%; d = 0.5). Our pilot data underpin the importance of resistance training independent of its specific movement pattern both for improving the endurance cycling performance and maximal leg strength. Further research should corroborate our preliminary findings on whether sprint cycling benefits favorably from AUL resistance training.

Grey Relational Analysis of Lower Limb Muscle Fatigue and Pedalling Performance Decline of Elite Athletes during a 30-Second All-Out Sprint Cycling Exercise

The 30-second all-out sprint cycling exercise is a classical sport capacity evaluation method, which may cause severe lower limb muscle fatigue. However, the relationship between lower limb muscle fatigue and the decline in exercise performance during 30-second sprint cycling remains unclear. In this study, ten cyclists volunteered to participate in a 30-second all-out sprint cycling while power, cadence, and surface electromyographic (EMG) signals of eight lower limb muscles were recorded during the exercise. EMG mean frequency (MNF) of each lower limb muscle group was computed for every 3-second epoch based on wavelet packet transformation. Grey relational grades between pedalling performance and the EMG MNF of each lower limb muscle group during the whole process were calculated. The results demonstrated that EMG MNF of the rectus femoris (RF), vastus (VAS), gastrocnemius (GAS), and tibialis anterior (TA) progressively tired during a 30-second all-out sprint cycling exercise. Of the muscles evaluated, the degree of fatigue of TA showed the greatest association with exercise performance decline, whereas the muscle fatigue of RF, VAS, and GAS also significantly impacted exercise performance during a 30-second all-out sprint cycling exercise.

The Aerobic and Anaerobic Contribution During Repeated 30-s Sprints in Elite Cyclists

Although the ability to sprint repeatedly is crucial in road cycling races, the changes in aerobic and anaerobic power when sprinting during prolonged cycling has not been investigated in competitive elite cyclists. Here, we used the gross efficiency (GE)-method to investigate: (1) the absolute and relative aerobic and anaerobic contributions during 3 × 30-s sprints included each hour during a 3-h low-intensity training (LIT)-session by 12 cyclists, and (2) how the energetic contribution during 4 × 30-s sprints is affected by a 14-d high-volume training camp with (SPR, n = 9) or without (CON, n = 9) inclusion of sprints in LIT-sessions. The aerobic power was calculated based on GE determined before, after sprints, or the average of the two, while the anaerobic power was calculated by subtracting the aerobic power from the total power output. When repeating 30-s sprints, the mean power output decreased with each sprint (p < 0.001, ES:0.6-1.1), with the majority being attributed to a decrease in mean anaerobic power (first vs. second sprint: -36 ± 15 W, p < 0.001, ES:0.7, first vs. third sprint: -58 ± 16 W, p < 0.001, ES:1.0). Aerobic power only decreased during the third sprint (first vs. third sprint: -17 ± 5 W, p < 0.001, ES:0.7, second vs. third sprint: 16 ± 5 W, p < 0.001, ES:0.8). Mean power output was largely maintained between sets (first set: 786 ± 30 W vs. second set: 783 ± 30 W, p = 0.917, ES:0.1, vs. third set: 771 ± 30 W, p = 0.070, ES:0.3). After a 14-d high-volume training camp, mean power output during the 4 × 30-s sprints increased on average 25 ± 14 W in SPR (p < 0.001, ES:0.2), which was 29 ± 20 W more than CON (p = 0.008, ES: 0.3). In SPR, mean anaerobic power and mean aerobic power increased by 15 ± 13 W (p = 0.026, ES:0.2) and by 9 ± 6 W (p = 0.004, ES:0.2), respectively, while both were unaltered in CON. In conclusion, moderate decreases in power within sets of repeated 30-s sprints are primarily due to a decrease in anaerobic power and to a lesser extent in aerobic power. However, the repeated sprint-ability (multiple sets) and corresponding energetic contribution are maintained during prolonged cycling in elite cyclists. Including a small number of sprints in LIT-sessions during a 14-d training camp improves sprint-ability mainly through improved anaerobic power.

Effects of including sprints during prolonged cycling on hormonal and muscular responses and recovery in elite cyclists

This study investigated the acute effects of including 30‐second sprints during prolonged low‐intensity cycling on muscular and hormonal responses and recovery in elite cyclists. Twelve male cyclists (VO_2max, 73.4 ± 4.0 mL/kg/min) completed a randomized crossover protocol, wherein 4 hours of cycling at 50% of VO_2max were performed with and without inclusion of three sets of 3 × 30 seconds maximal sprints (E&S vs E, work‐matched). Muscle biopsies (m. vastus lateralis) and blood were sampled at Pre, immediately after (Post) and 3 hours after (3 h) finalizing sessions. E&S led to greater increases in mRNA levels compared with E for markers of fat metabolism (PDK4, Δ‐Log2 fold change between E&S and E ± 95%CI Post; 2.1 ± 0.9, Δ3h; 1.3 ± 0.7) and angiogenesis (VEGFA, Δ3h; 0.3 ± 0.3), and greater changes in markers of muscle protein turnover (myostatin, ΔPost; −1.4 ± 1.2, Δ3h; −1.3 ± 1.3; MuRF1, ΔPost; 1.5 ± 1.2, all P < .05). E&S showed decreased mRNA levels for markers of ion transport at 3h (Na⁺‐K⁺ α1; −0.6 ± 0.6, CLC1; −1.0 ± 0.8 and NHE1; −0.3 ± 0.2, all P < .05) and blunted responses for a marker of mitochondrial biogenesis (PGC‐1α, Post; −0.3 ± 0.3, 3h; −0.4 ± 0.3, P < .05) compared with EE&S and E showed similar endocrine responses, with exceptions of GH and SHBG, where E&S displayed lower responses at Post (GH; −4.1 ± 3.2 μg/L, SHBG; −2.2 ± 1.9 nmol/L, P < .05). Both E&S and E demonstrated complete recovery in isokinetic knee extension torque 24 hours after exercise. In conclusion, we demonstrate E&S to be an effective exercise protocol for elite cyclists, which potentially leads to beneficial adaptations in skeletal muscle without impairing muscle recovery 24 hours after exercise.