Low‐load blood‐flow‐restriction resistance training (LL‐BFR‐RT) is gaining popularity, but its physiological effects remain unclear. This study aimed to compare LL‐BFR‐RT with low‐load resistance exercise (LL‐RT) and high‐load resistance exercise (HL‐RT) on metabolism, electrolytes, and ions in the lower extremities by invasive catheter measurements, which are crucial for risk assessment. Ten healthy men (27.6 ± 6.4 years) completed three trials of knee‐extensor exercises with LL‐RT (30% 1RM), LL‐BFR‐RT (30% 1RM, 50% limb occlusion pressure), and HL‐RT (75% 1RM). The exercise protocol consisted of four sets to voluntary muscle failure with 1 min of rest between sets. Blood gas analysis was collected before, during, and after each trial through intravenous catheters at the exercising leg. LL‐BFR‐RT had lower total workload (1274 ± 237 kg, mean ± SD) compared to LL‐RT (1745 ± 604 kg), and HL‐RT (1847 ± 367 kg, p < 0.01), with no difference between LL‐RT and HL‐RT. Pain perception did not differ significantly. Exercise‐induced drop in oxygen partial pressure, lactate accumulation and electrolyte shifts (with increased [K⁺]) occurred during under all conditions (p < 0.001). Creatine kinase and lactate dehydrogenase increased significantly 24‐ and 48‐h postexercise under all three conditions (p < 0.001). This study, using invasive catheter measurements, found no significant differences in metabolic, ionic, and electrolyte responses among LL‐BFR‐RT, LL‐RT, and HL‐RT when exercised to voluntary muscular failure. LL‐BFR‐RT reduced time to failure without specific physiological responses.

Purpose: Understanding physiological determinants of lactate threshold 2 (LT2) is crucial for tracking adaptations and deriving individualized training recommendations in cycling. Therefore, the study investigated: 1. the accuracy of modeling power output at LT2 in young athletes of both sexes using maximal oxygen uptake ( $${\dot{V}}\textrm{O}_{2_\textrm{peak}}$$ V ˙ O 2 peak ), fractional utilization of $${\dot{V}}\textrm{O}_{2_\textrm{peak}}$$ V ˙ O 2 peak (% $${\dot{V}}\textrm{O}_{2_\textrm{peak}}$$ V ˙ O 2 peak ), and oxygen cost of cycling (Cc); 2. the influence of Cc determination on the model accuracy; 3. the influence of the model predictors and inclusion of maximal lactate accumulation rate ( $${\dot{c}}La_\textrm{max}$$ c ˙ L a max ) on power at LT2 depending on sex. Methods: Eighty-three cyclists and triathletes (22 females, 61 males; age [median and IQR]: 14.6 [13.8–17.6] years, $${\dot{V}}\textrm{O}_{2_\textrm{peak}}$$ V ˙ O 2 peak [mean ± SD]: 59.2 ± 6.5 mL⋅kg^–1⋅min^–1) performed an incremental test to determine power at LT2, $${\dot{V}}\textrm{O}_{2_\textrm{peak}},$$ V ˙ O 2 peak , % $${\dot{V}}\textrm{O}_{2_\textrm{peak}}$$ V ˙ O 2 peak at LT2, and Cc (assessed at 3 W⋅kg^–1, 75% $${\dot{V}}\textrm{O}_{2_\textrm{peak}},$$ V ˙ O 2 peak , and 90% LT2). Results: Modeled and experimentally determined power at LT2 demonstrated excellent agreement for all, male and female athletes (ICC $$\ge$$ ≥ 0.961), with Cc at 90% LT2 providing the highest accuracy (ICC $$\ge$$ ≥ 0.986). The three physiological determinants explained $$\ge$$ ≥ 98% of the variance in power at LT2, with the largest unique contribution from $${\dot{V}}\textrm{O}_{2_\textrm{peak}}$$ V ˙ O 2 peak (62 and 67% of total $$R^2$$ R 2 ), followed by Cc (8 and 34%) and % $${\dot{V}}\textrm{O}_{2_\textrm{peak}}$$ V ˙ O 2 peak at LT2 (5 and 12%) in males and females, respectively, while $${\dot{c}}La_\textrm{max}$$ c ˙ L a max did not improve the regression. Conclusion: $${\dot{V}}\textrm{O}_{2_\textrm{peak}}, $$ V ˙ O 2 peak , % $${\dot{V}}\textrm{O}_{2_\textrm{peak}}$$ V ˙ O 2 peak at LT2 and Cc accurately predict power at LT2 in young cycling athletes independent of sex, with determination of Cc at 90% LT2 providing the highest accuracy. While $${\dot{V}}\textrm{O}_{2_\textrm{peak}}$$ V ˙ O 2 peak contributes most to LT2 in both sexes, Cc appears more important in young females.

Purpose: This study aimed to investigate: 1. The influence of sex and age on the accuracy of the classical model of endurance performance, including maximal oxygen uptake ( $$\dot{V}\mathrm{O}_{2}\mathrm{peak}$$V ˙ O 2 peak ), its fraction (LT2_%), and cost of running (C_R), for calculating running speed at lactate threshold 2 (vLT2) in young athletes. 2. The impact of different C_R determination methods on the accuracy of the model. 3. The contributions of $$\dot{V}\mathrm{O}_{2}\mathrm{peak}$$V ˙ O 2 peak , LT2_%, and C_R to vLT2 in different sexes. Methods: 45 male and 55 female young squad athletes from different sports (age: 15.4 ± 1.3 years; $$\dot{V}\mathrm{O}_{2}\mathrm{peak}$$V ˙ O 2 peak : 51.4 ± 6.8 $$\hbox {mL} \cdot \hbox {kg}^{-1} \cdot \hbox {min}^{-1}$$mL · kg - 1 · min - 1 ) performed an incremental treadmill test to determine $$\dot{V}\mathrm{O}_{2}\mathrm{peak}$$V ˙ O 2 peak , LT2_%, C_R, and vLT2. C_R was assessed at a fixed running speed (2.8 $$ \hbox {m} \cdot \hbox {s}^{-1} $$m · s - 1 ), at lactate threshold 1 (LT1), and at 80% of $$\dot{V}\mathrm{O}_{2}\mathrm{peak}$$V ˙ O 2 peak , respectively. Results: Experimentally determined and modeled vLT2 were highly consistent independent of sex and age (ICC $$\ge$$≥ 0.959). The accuracy of vLT2 modeling was improved by reducing random variation using individualized C_R at 80% $$\dot{V}\mathrm{O}_{2}\mathrm{peak}$$V ˙ O 2 peak (± 4%) compared to C_R at LT1 (± 7%) and at a fixed speed (± 8%). 97% of the total variance of vLT2 was explained by $$\dot{V}\mathrm{O}_{2}\mathrm{peak}$$V ˙ O 2 peak , LT2_%, and C_R. While $$\dot{V}\mathrm{O}_{2}\mathrm{peak}$$V ˙ O 2 peak and C_R showed the highest unique (96.5% and 31.9% of total $$R^2$$R 2 , respectively) and common (– 31.6%) contributions to the regression model, LT2_% made the smallest contribution (7.5%). Conclusion: Our findings indicate: 1. High accuracy of the classical model of endurance performance in calculating vLT2 in young athletes independent of age and sex. 2. The importance of work rate selection in determining C_R to accurately predict vLT2. 3. The largest contribution of $$\dot{V}\mathrm{O}_{2}\mathrm{peak}$$V ˙ O 2 peak and C_R to vLT2, the latter being more important in female athletes than in males, and the least contribution of LT2_%.

Background and Objectives: This study aimed to compare the calculated running velocity at the anaerobic lactate threshold (cLT_An), determined by a mathematical model for metabolic simulation, with two established threshold concepts (onset of blood lactate accumulation (OBLA; 4 mmol∙L⁻¹) and modified maximal deviation method (mDmax)). Additionally, all threshold concepts were correlated with performance in different endurance running events. Materials and Methods: Ten sub-elite runners performed a 30 s sprint test on a cycle ergometer adjusted to an isokinetic mode set to a cadence of 120 rpm to determine maximal lactate production rate (VLa_max), and a graded exercise test on a treadmill to determine maximal oxygen uptake (VO_2max). Running velocities at OBLA, mDmax, and cLT_An were then compared with each other, and further correlated with running performance over various distances (3000 m, 5000 m, and 10,000 m). Results: The mean difference in cLT_An was −0.13 ± 0.43 m∙s⁻¹ and −0.32 ± 0.39 m∙s⁻¹ compared to mDmax (p = 0.49) and OBLA (p < 0.01), respectively. cLT_An indicated moderate to good concordance with the established threshold concepts (mDmax: ICC = 0.87, OBLA: ICC = 0.74). In comparison with other threshold concepts, cLT_An exhibited comparable correlations with the assessed running performances (cLT_An: r = 0.61–0.76, mDmax: r = 0.69–0.79, OBLA: r = 0.56–0.69). Conclusion: Our data show that cLT_An can be applied for determining endurance performance during running. Due to the consideration of individual physiological profiles, cLT_An offers a physiologically justified approach to assess an athlete’s endurance performance.

Despite growing interest in blood flow restriction (BFR) for enhancing training adaptations, its acute impacts on local and systemic physiological stress remain incompletely understood. This study compared the metabolic and perceptual responses of low‐intensity cycling (LI) with BFR (LI + BFR) to both LI and high‐intensity (HI) cycling without BFR, matched for time and external work. Ten males (26.9 ± 4.6 years) completed LI (20 min at 55% peak aerobic power output, PPO), LI + BFR (with 50% limb occlusion pressure), and HI (10 × 1 min at 90% PPO interspersed with 1‐min recovery at 20% PPO) protocols in a randomized cross‐over design. Interstitial metabolic responses were assessed via microdialysis in the vastus lateralis; systemic blood responses were evaluated via venous blood gas analysis. Cardiorespiratory responses, including heart rate, oxygen uptake, and ventilation, were continuously monitored during exercise. Serum creatine kinase (CK) and lactate dehydrogenase (LDH) were measured as indirect markers of muscle damage, and perceptual responses were documented. Muscle interstitial lactate and pyruvate were highest in HI, followed by LI + BFR, and lowest in LI ( p < 0.05). Systemic blood and cardiorespiratory responses were comparable between LI + BFR and HI and exceeded LI ( p < 0.05), while electrolyte shifts occurred across all conditions ( p < 0.001) without between‐condition differences. All protocols increased CK and LDH 24–48 h post‐exercise, with the greatest increases in HI ( p < 0.05). Perceived exertion and pain were higher in LI + BFR than in other conditions ( p < 0.05). In conclusion, BFR intensifies local and systemic stress during LI and may be a potent strategy to promote muscle adaptive stimulus. However, when time and total external work are matched, high mechanical loading appears more effective in inducing local stress, which may be essential for further muscular adaptation processes.

Strength training responses are influenced by sets, repetitions, and mechanical load, whereas Blood Flow Restriction (BFR) training adds the variable of temporarily restricting blood flow via a tourniquet. This has intensified scientific discussions regarding the vascular responses and thereby safety of the BFR method. To address these concerns, we investigated intravascular pressure changes during low‐load (LL‐RT), low‐load with BFR (LL‐BFR‐RT), and high‐load (HL‐RT) exercise. Ten healthy men (26.8 ± 4.59 years) performed unilateral biceps curls to failure in a randomized cross‐over design: (1) LL‐RT (30% 1RM), (2) LL‐BFR‐RT (30% 1RM, 50% LOP), and (3) HL‐RT (75% 1RM). Total workload was significantly higher in LL‐RT (692 ± 251 kg) compared to LL‐BFR‐RT (378 ± 58.7 kg) and HL‐RT (327 ± 65.1 kg, p < 0.001). In terms of mean values, LL‐BFR‐RT resulted in higher diastolic and mean arterial pressures during rest periods between sets compared to other conditions (p ≤ 0.02). Both LL‐RT and LL‐BFR‐RT led to longer durations spent at increased diastolic (above 90 mmHg, LL‐RT: ~419 s vs. LL‐BFR‐RT: ~356 s vs. Hl‐RT: ~122 s), systolic (above 140 mmHg, LL‐RT: ~437 s vs. LL‐BFR‐RT: ~336 s vs. HL‐RT: ~199 s), and mean arterial pressures (above 107 mmHg, LL‐RT: ~451 s vs. LL‐BFR‐RT: ~384 s vs. HL‐RT: ~168 s) compared to HL‐RT (p ≤ 0.028). Relative to total exercise time, LL‐BFR‐RT resulted in higher proportion of time spent at elevated diastolic (above 90 mmHg, LL‐RT: ~56.5% vs. LL‐BFR‐RT: ~68.7% vs. Hl‐RT: ~33.5%) and mean arterial pressures (above 107 mmHg, LL‐RT: ~60.8% vs. LL‐BFR‐RT: ~74.0% vs. HL‐RT: ~45.7%) compared to HL‐RT (p ≤ 0.034). Peripheral venous pressure was significantly higher in LL‐BFR‐RT compared to other conditions (p < 0.001), with both absolute and relative time spent at higher pressures (above 75 mmHg, LL‐RT: ~57.0 s and ~ 9.12% vs. LL‐BFR‐RT: ~424 s and ~ 81.7% vs. HL‐RT: ~36.0 s and ~ 8.99%, p ≤ 0.002). Our results suggest that BFR training performed to failure imposes greater arterial and venous stress in the exercising limb compared to high‐load training without BFR, particularly due to prolonged exposure to elevated pressures. Further research is needed to assess the potential risks of elevated local arterial and venous pressure responses by frequent BFR use, particularly in populations with pre‐existing medical conditions.