Energy System Contribution during 1500M Running in Untrained and Endurance-Trained Asian Male College Students

OBJECTIVES To compare the aerobic and anaerobic energy system contribution during 1500m running between collegiate untrained (UT) and endurance trained (ET) subjects.METHODS Five Asian UT (age: 23.8 ± 0.4 yrs, body fat %: 15.9 ± 5.7 %, height: 174.0 ± 4.1 cm, weight: 65.5 ± 4.1 kg) and 5 Asian ET male participants (age: 24.4 ± 3.9 yrs, body fat %: 12.9 ± 6.9 %, height: 169.4 ± 5.1 cm, weight: 60.6 ± 8.1 kg) participated in this study. Participants attended 3 sessions to determine their body composition, submaximal and maximal oxygen consumption (VO_2max) test, 1500m track running session (RS) and 1500m treadmill RS. The maximally accumulated oxygen deficit (MAOD) method was used to calculate energy system contribution.RESULTS The times for the 1500m track run for the UT and ET were 428.0 ± 48.7 and 331.6 ± 14.0 seconds (p=0.004) respectively. There were no significant differences in VO₂ between the 1500m track and treadmill RS indicating the participants ran to their personal best times for both trials. The mean VO_2max(mL•kg^-1•min^-1) were significantly different between UT (45.1 ± 5.0) and ET participants (58.3 ± 2.2) (p=0.002). The mean relative contributions of the aerobic and anaerobic energy system during 1500m running were significantly different for the UT, 65.4 ± 7.0%, 34.6 ± 7.0 and ET, 75.7 ± 1.5%, 24.3 ± 1.5 % (p =0.011).CONCLUSIONS The point of equal contribution of the aerobic and the anaerobic systems occurred after thirty to forty seconds of intensive exhaustive running after which the aerobic contribution continues to increase while the anaerobic contribution decreases with increasing duration. By the end of 60th second of exhaustive running, the ET mean aerobic contribution is 71.5% compared to the UT’s 58.6%. This finding suggests a greater reliance on the aerobic energy system by the ET.

Determination of Maximum Accumulated Oxygen Deficit Using Backward Extrapolation

This study aimed to compare the Maximum Accumulated Oxygen Deficit determined by the conventional method (MAODC) with that determined by the backward extrapolation technique (MAODEXTR) in runners. Fourteen runners underwent a maximal incremental test for determination of iVO2MAX, ten submaximal efforts (50–95% of iVO2MAX for 7 min). During the submaximal efforts oxygen consumption (VO2) values were obtained conventionally and through the backward extrapolation technique (~ 3 s after the end of each effort). A supramaximal effort (110% of iVO2MAX) (tLimC) and five supramaximal bouts (tLimEXTR) were performed. MAODC and MAODEXTR were determined from the difference between the VO2 accumulated during tLimC and tLimEXTR and the predicted values. The tLimC was lower than tLimEXTR (164.06±36.32 s, 200.23±63.78 s, p<0.05). No significant differences were found between absolute and relative MAODC and MAODEXTR values, however, low intraclass correlations (0.26 and 0.24), high typical errors (2.03 L and 24 mL∙kg−1) were observed, and coefficients of variation (46 and 48%), respectively. The graphical analysis of the differences showed agreement and correlation between the methods (r=0.86 and 0.85). Thus, it can be concluded that the MAODEXTR is not a valid method for estimating the anaerobic capacity of runners, moreover, unreliable.

Non-oxidative Energy Supply Correlates with Lactate Transport and Removal in Trained Rowers

This study aimed to test if the non-oxidative energy supply (estimated by the accumulated oxygen deficit) is associated with an index of muscle lactate accumulation during exercise, muscle monocarboxylate transporter content and the lactate removal ability during recovery in well-trained rowers. Seventeen rowers completed a 3-min all-out exercise on rowing ergometer to estimate the accumulated oxygen deficit. Blood lactate samples were collected during the subsequent passive recovery to assess individual blood lactate curves, which were fitted to the bi-exponential time function: La(t)= [La](0)+A1·(1–e–γ 1 t)+A2·(1–e–γ 2 t), where the velocity constants γ1 and γ2 (min–1) denote the lactate exchange and removal abilities during recovery, respectively. The accumulated oxygen deficit was correlated with the net amount of lactate released from the previously active muscles (r =0.58, P<0.05), the monocarboxylate transporters MCT1 and MCT4 (r=0.63, P<0.05) and γ2 (r=0.55, P<0.05). γ2 and the lactate release rate at exercise completion were negatively correlated with citrate synthase activity. These findings suggest that the capacity to supply non-oxidative energy during supramaximal rowing exercise is associated with muscle lactate accumulation and transport, as well as lactate removal ability.

Decrescent intensity training concurrently improves maximal anaerobic power, maximal accumulated oxygen deficit, and maximal oxygen uptake

This study aimed to investigate the effects of a gradually decreasing intensity training from that corresponding to maximal anaerobic power (MAnP) to that of near maximal oxygen uptake () (decrescent intensity training) on MAnP, maximal accumulated oxygen deficit (MAOD), and in untrained young men. Seventeen untrained young men were randomly divided into either a training (TR; n = 9) group or a control (CON; n = 8) group. The TR group performed the decrescent intensity training, whereas the CON group did not perform any exercises. The mean training time per session throughout the training period was 275 ± 135 s. There was a Group × Time interaction for both absolute and relative (p < 0.01) values of , MAOD, and MAnP. The TR group had significantly increased values for all variables after the 8-week training program, and the relative values of all variables were significantly higher in the TR group than in the CON group. Muscle thicknesses in the anterior and posterior aspects of the thigh and maximal isokinetic knee extension and flexion strengths improved only in the TR group (p < 0.05). A single-exercise training with gradually decreasing intensity from that corresponding to the MAnP to that of approximately 100% improves MAnP, MAOD, and concurrently, despite the short training time per session.

Assessment of high-intensity over-ground conditioning and simulated racing on aerobic and anaerobic capacities in racehorses

A prospective, randomised study assessed the impact of high-intensity racetrack conditioning on aerobic and anaerobic capacities in seasoned Thoroughbred racehorses. The effect of 10 weeks race conditioning and two simulated races on V̇O2max and maximum accumulated oxygen deficit (MAOD) were evaluated. An incremental treadmill test to determine V̇O2max, followed by three supramaximal runs to fatigue (at speeds (V105%, V115%, V125%) corresponding to oxygen requirements 105%, 115% and 125% of V̇O2max, in randomised order) were performed at each timepoint (T1 [pre-conditioning] and T2 [post-conditioning]). Prior to T1, racehorses were briefly de-trained for four-six weeks and given low-level treadmill conditioning to prepare them for the more strenuous race conditioning after T1. Paired variables between T1 and T2 were analysed using a paired t-test. A 2-way RM ANOVA compared variables with >1 measurement. Speed at V̇O2max (P=0.04) and V̇O2max (P=0.01) increased with conditioning. Calculated speeds for the supramaximal runs increased for V105% (P=0.02) and V115% (P=0.03) but not for V125% (P=0.08). There was no conditioning effect on time to fatigue (P=0.34), although it was different between all intensities (2.8, 2.2 and 1.4 mins at V105%, V115% and V125% respectively at T2). O2 demand increased with conditioning (P=0.02) for each supramaximal intensity. On average, horses’ aerobic capacity improved 4.43% after conditioning. MAOD was unchanged with conditioning (P=0.25) and unaffected by exercise intensity. Fit racehorses that have undergone repeated intensive training programs, experience smaller, incremental improvement than completely unfit horses. The anaerobic capacity of previously trained racehorses is relatively stable, despite brief periods of de-training.

Remote ischemic preconditioning increases accumulated oxygen deficit in middle-distance runners

The mediators underlying the putative benefits of remote ischemic preconditioning (IPC) on dynamic whole body exercise performance have not been widely investigated. Our objective was to test the hypothesis that remote IPC improves supramaximal exercise performance in National Collegiate Athletic Association (NCAA) Division I middle-distance runners by increasing accumulated oxygen deficit (AOD), an indicator of glycolytic capacity. A randomized sham-controlled crossover study was employed. Ten NCAA Division I middle-distance athletes [age: 21 ± 1 yr; maximal oxygen uptake (V̇o2max): 65 ± 7 ml·kg−1·min−1] completed three supramaximal running trials (baseline, after mock IPC, and with remote IPC) at 110% V̇o2max to exhaustion. Remote IPC was induced in the right arm with 4 × 5 min cycles of brachial artery ischemia with 5 min of reperfusion. Supramaximal AOD (ml/kg) was calculated as the difference between the theoretical oxygen demand required for the supramaximal running bout (linear regression extrapolated from ~12 × 5 min submaximal running stages) and the actual oxygen demand for these bouts. Remote IPC [122 ± 38 s, 95% confidence interval (CI): 94–150] increased ( P < 0.001) time to exhaustion 22% compared with baseline (99 ± 23 s, 95% CI: 82–116, P = 0.014) and sham (101 ± 30 s, 95% CI: 80–123, P = 0.001). In the presence of IPC, AOD was 47 ± 36 ml/kg (95% CI: 20.8–73.9), a 29% increase compared with baseline (36 ± 28 ml/kg, 95% CI: 16.3–56.9, P = 0.008) and sham (38 ± 32 ml/kg, 95% CI: 16.2–63.0, P = 0.024). Remote IPC considerably improved supramaximal exercise performance in NCAA Division I middle-distance athletes. Greater glycolytic capacity, as estimated by increased AOD, is a potential mediator for these performance improvements. NEW & NOTEWORTHY Our novel findings indicate that ischemic preconditioning enhanced glycolytic exercise capacity, enabling National Collegiate Athletic Association (NCAA) middle-distance track athletes to run ~22 s longer before exhaustion compared with baseline and mock ischemic preconditioning. The increase in “all-out” performance appears to be due to increased accumulated oxygen deficit, an index of better supramaximal capacity. Of note, enhanced exercise performance was demonstrated in a specific group of in-competition NCAA elite athletes that has already undergone substantial training of the glycolytic energy systems.