The efficacy of downhill running as a method to enhance running economy in trained distance runners

Running downhill, in comparison to running on the flat, appears to involve an exaggerated stretch-shortening cycle (SSC) due to greater impact loads and higher vertical velocity on landing, whilst also incurring a lower metabolic cost. Therefore, downhill running could facilitate higher volumes of training at higher speeds whilst performing an exaggerated SSC, potentially inducing favourable adaptations in running mechanics and running economy (RE). This investigation assessed the efficacy of a supplementary 8-week programme of downhill running as a means of enhancing RE in well-trained distance runners. Nineteen athletes completed supplementary downhill (-5% gradient; n = 10) or flat (n = 9) run training twice a week for 8 weeks within their habitual training. Participants trained at a standardised intensity based on the velocity of lactate turnpoint (vLTP), with training volume increased incrementally between weeks. Changes in energy cost of running (E_C) and vLTP were assessed on both flat and downhill gradients, in addition to maximal oxygen uptake (⩒O_2max). No changes in E_C were observed during flat running following downhill (1.22 ± 0.09 vs 1.20 ± 0.07 Kcal kg^-1 km^-1, P = .41) or flat run training (1.21 ± 0.13 vs 1.19 ± 0.12 Kcal kg^-1 km^-1). Moreover, no changes in E_C during downhill running were observed in either condition (P > .23). vLTP increased following both downhill (16.5 ± 0.7 vs 16.9 ± 0.6 km h^-1_, P = .05) and flat run training (16.9 ± 0.7 vs 17.2 ± 1.0 km h^-1, P = .05), though no differences in responses were observed between groups (P = .53). Therefore, a short programme of supplementary downhill run training does not appear to enhance RE in already well-trained individuals.

Exercise duration-matched interval and continuous sprint cycling induce similar increases in AMPK phosphorylation, PGC-1α and VEGF mRNA expression in trained individuals

Purpose

The effects of low-volume interval and continuous ‘all-out’ cycling, matched for total exercise duration, on mitochondrial and angiogenic cell signalling was investigated in trained individuals.

Methods

In a repeated measures design, 8 trained males (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{O}}_{{2{\text{peak}}}}$$\end{document}V˙O2peak, 57 ± 7 ml kg⁻¹ min⁻¹) performed two cycling exercise protocols; interval (INT, 4 × 30 s maximal sprints interspersed by 4 min passive recovery) or continuous (CON, 2 min continuous maximal sprint). Muscle biopsies were obtained before, immediately after and 3 h post-exercise.

Results

Total work was 53 % greater (P = 0.01) in INT compared to CON (71.2 ± 7.3 vs. 46.3 ± 2.7 kJ, respectively). Phosphorylation of AMPK^Thr172 increased by a similar magnitude (P = 0.347) immediately post INT and CON (1.6 ± 0.2 and 1.3 ± 0.3 fold, respectively; P = 0.011), before returning to resting values at 3 h post-exercise. mRNA expression of PGC-1α (7.1 ± 2.1 vs. 5.5 ± 1.8 fold; P = 0.007), VEGF (3.5 ± 1.2 vs. 4.3 ± 1.8 fold; P = 0.02) and HIF-1α (2.0 ± 0.5 vs. 1.5 ± 0.3 fold; P = 0.04) increased at 3 h post-exercise in response to INT and CON, respectively; the magnitude of which were not different between protocols.

Conclusions

Despite differences in total work done, low-volume INT and CON ‘all-out’ cycling, matched for exercise duration, provides a similar stimulus for the induction of mitochondrial and angiogenic cell signalling pathways in trained skeletal muscle.

Acute and chronic effect of sprint interval training combined with postexercise blood-flow restriction in trained individuals

This investigation assessed the efficacy of sprint interval training (SIT) combined with postexercise blood-flow restriction as a novel approach to enhance maximal aerobic physiology and performance. In study 1, a between-groups design was used to determine whether 4 weeks (2 days per week) of SIT (repeated 30 s maximal sprint cycling) combined with postexercise blood-flow restriction (BFR) enhanced maximal oxygen uptake (V̇(O2max)) and 15 km cycling time-trial performance (15 km TT) compared with SIT alone (CON) in trained individuals. The V̇(O2max) increased after BFR by 4.5% (P = 0.01) but was unchanged after CON. There was no difference in 15 km TT performance after CON or BFR. In study 2, using a repeated-measures design, participants performed an acute bout of either BFR or CON. Muscle biopsies were taken before and after exercise to examine the activation of signalling pathways regulating angiogenesis and mitochondrial biogenesis. Phosphorylation of p38MAPK(Thr180/Tyr182) increased by a similar extent after CON and BFR. There was no difference in the magnitude of increase in PGC-1α, VEGF and VEGFR-2 mRNA expression between protocols; however, HIF-1α mRNA expression increased (P = 0.04) at 3 h only after BFR. We have demonstrated the potency of combining BFR with SIT in increasing V̇(O2max) in trained individuals, but this did not translate to an enhanced exercise performance. Sprint interval training alone did not induce any observable adaptation. Although the mechanisms are not fully understood, we present preliminary evidence that BFR leads to enhanced HIF-1α-mediated cell signalling.

The valid measurement of running economy in runners

Oxygen cost (OC) is commonly used to assess an athlete's running economy, although the validity of this measure is often overlooked.

PURPOSE

This study evaluated the validity of OC as a measure of running economy by comparison with the underlying energy cost (EC). In addition, the most appropriate method of removing the influence of body mass was determined to elucidate a measure of running economy that enables valid interindividual comparisons.

METHODS

One hundred and seventy-two highly trained endurance runners (males, n = 101; females, n = 71) performed a discontinuous submaximal running assessment, consisting of approximately seven 3-min stages (1 km·h increments), to determine the absolute OC (L·km) and EC (kcal·km) for the four speeds below lactate turn point.

RESULTS

Comparisons between models revealed linear ratio scaling to be a more suitable method than power function scaling for removing the influence of body mass for both EC (males, R = 0.589 vs 0.588; females, R = 0.498 vs 0.482) and OC (males, R = 0.657 vs 0.652; females, R = 0.532 vs 0.531). There were stepwise increases in EC and RER with increments in running speed (both, P < 0.001). However, no differences were observed for OC across the four monitored speeds (P = 0.54).

CONCLUSIONS

Although EC increased with running speed, OC was insensitive to changes in running speed and, therefore, does not appear to provide a valid index of the underlying EC of running, likely due to the inability of OC to account for variations in substrate use. Therefore, EC should be used as the primary measure of running economy, and for runners, an appropriate scaling with body mass is recommended.

The correlation between running economy and maximal oxygen uptake: cross-sectional and longitudinal relationships in highly trained distance runners

A positive relationship between running economy and maximal oxygen uptake (V̇O2max) has been postulated in trained athletes, but previous evidence is equivocal and could have been confounded by statistical artefacts. Whether this relationship is preserved in response to running training (changes in running economy and V̇O2max) has yet to be explored. This study examined the relationships of (i) running economy and V̇O2max between runners, and (ii) the changes in running economy and V̇O2max that occur within runners in response to habitual training. 168 trained distance runners (males, n = 98, V̇O2max 73.0 ± 6.3 mL∙kg-1∙min-1; females, n = 70, V̇O2max 65.2 ± 5.9 mL kg-1∙min-1) performed a discontinuous submaximal running test to determine running economy (kcal∙km-1). A continuous incremental treadmill running test to volitional exhaustion was used to determine V̇O2max 54 participants (males, n = 27; females, n = 27) also completed at least one follow up assessment. Partial correlation analysis revealed small positive relationships between running economy and V̇O2max (males r = 0.26, females r = 0.25; P<0.006), in addition to moderate positive relationships between the changes in running economy and V̇O2max in response to habitual training (r = 0.35; P<0.001). In conclusion, the current investigation demonstrates that only a small to moderate relationship exists between running economy and V̇O2max in highly trained distance runners. With >85% of the variance in these parameters unexplained by this relationship, these findings reaffirm that running economy and V̇O2max are primarily determined independently.

Tapering strategies in elite British endurance runners

The aim of the study was to explore pre-competition training practices of elite endurance runners. Training details from elite British middle distance (MD; 800 m and 1500 m), long distance (LD; 3000 m steeplechase to 10,000 m) and marathon (MAR) runners were collected by survey for 7 days in a regular training (RT) phase and throughout a pre-competition taper. Taper duration was [median (interquartile range)] 6 (3) days in MD, 6 (1) days in LD and 14 (8) days in MAR runners. Continuous running volume was reduced to 70 (16)%, 71 (24)% and 53 (12)% of regular levels in MD, LD and MAR runners, respectively (P < 0.05). Interval running volume was reduced compared to regular training (MD; 53 (45)%, LD; 67 (23)%, MAR; 64 (34)%, P < 0.05). During tapering, the peak interval training intensity was above race speed in LD and MAR runners (112 (27)% and 114 (3)%, respectively, P < 0.05), but not different in MD (100 (2)%). Higher weekly continuous running volume and frequency in RT were associated with greater corresponding reductions during the taper (R = -0.70 and R = -0.63, respectively, both P < 0.05). Running intensity during RT was positively associated with taper running intensity (continuous intensity; R = 0.97 and interval intensity; R = 0.81, both P < 0.05). Algorithms were generated to predict and potentially prescribe taper content based on the RT of elite runners. In conclusion, training undertaken prior to the taper in elite endurance runners is predictive of the tapering strategy implemented before competition.

The reliability of running economy expressed as oxygen cost and energy cost in trained distance runners

This study assessed the between-test reliability of oxygen cost (OC) and energy cost (EC) in distance runners, and contrasted it with the smallest worthwhile change (SWC) of these measures. OC and EC displayed similar levels of within-subject variation (typical error < 3.85%). However, the typical error (2.75% vs 2.74%) was greater than the SWC (1.38% vs 1.71%) for both OC and EC, respectively, indicating insufficient sensitivity to confidently detect small, but meaningful, changes in OC and EC.

Modelling the determinants of 2000 m rowing ergometer performance: a proportional, curvilinear allometric approach

Previous studies have investigated the determinants of indoor rowing using correlations and linear regression. However, the power demands of ergometer rowing are proportional to the cube of the flywheel's (and boat's) speed. A rower's speed, therefore, should be proportional to the cube root (0.33) of power expended. Hence, the purpose of the present study was to explore the relationship between 2000 m indoor rowing speed and various measures of power of 76 elite rowers using proportional, curvilinear allometric models. The best single predictor of 2000 m rowing ergometer performance was power at VO(2max)(WVO(2max))(0.28), that explained R(2)=95.3% in rowing speed. The model realistically describes the greater increment in power required to improve a rower's performance by the same amount at higher speeds compared with that at slower speeds. Furthermore, the fitted exponent, 0.28 (95% confidence interval 0.226-0.334) encompasses 0.33, supporting the assumption that rowing speed is proportional to the cube root of power expended. Despite an R(2)=95.3%, the initial model was unable to explain "sex" and "weight-class" differences in rowing performances. By incorporating anaerobic as well as aerobic determinants, the resulting curvilinear allometric model was common to all rowers, irrespective of sex and weight class.

Sodium bicarbonate improves swimming performance

Sodium bicarbonate ingestion has been shown to improve performance in single-bout, high intensity events, probably due to an increase in buffering capacity, but its influence on single-bout swimming performance has not been investigated. The effects of sodium bicarbonate supplementation on 200 m freestyle swimming performance were investigated in elite male competitors. Following a randomised, double blind counterbalanced design, 9 swimmers completed maximal effort swims on 3 separate occasions: a control trial (C); after ingestion of sodium bicarbonate (SB: NaHCO3 300 mg . kg (-1) body mass); and after ingestion of a placebo (P: CaCO3 200 mg . kg (-1) body mass). The SB and P agents were packed in gelatine capsules and ingested 90 - 60 min prior to each 200 m swim. Mean 200 m performance times were significantly faster for SB than C or P (1 : 52.2 +/- 4.7; 1 : 53.7 +/- 3.8; 1 : 54.0 +/- 3.6 min : ss; p < 0.05). Base excess, pH and blood bicarbonate were all elevated pre-exercise in the SB compared to C and P trials (p < 0.05). Post-200 m blood lactate concentrations were significantly higher following the SB trial compared with P and C (p < 0.05). It was concluded that SB supplementation can improve 200 m freestyle performance time in elite male competitors, most likely by increasing buffering capacity.

Comparison of the Oxygen Uptake Kinetics of Club and Olympic Champion Rowers

PURPOSE

To test the hypothesis that elite rowers would possess a faster, more economic oxygen uptake response than club standard rowers.

METHODS

Eight Olympic champion (ELITE) rowers were compared with a cohort of eight club standard (CLUB) rowers. Participants completed a progressive exercise test to exhaustion, repeated 6-min moderate and heavy square-wave transitions, and a maximal 2000-m ergometer time trial.

RESULTS

The time constant (tau) of the primary component (PC) was faster for the ELITE group compared with CLUB for moderate-intensity (13.9 vs 19.4 s, P = 0.02) and heavy-intensity (18.7 vs 22.4 s, P = 0.005) exercise. ELITE rowers consumed less oxygen for moderate (14.2 vs 15.6 mL x min(-1) x W(-1); P = 0.009) and heavy (12.1 vs 13.7 mL x min(-1) x W(-1); P = 0.01) exercise. A greater absolute slow component was observed in the ELITE group (P = 0.009), but no differences were noted when the slow component was expressed relative to work rate performed (P = 0.14). Intergroup correlation with time trial performance speed was significant for tauPC during heavy-intensity exercise (r = -0.59, P = 0.02).

CONCLUSIONS

Compared with CLUB rowers, the shorter time constant response and greater economy observed in ELITE rowers may suggest advantageous adjustment of oxidative processes from rest to work. Training status or performance level do not seem to be associated with a smaller slow component when comparing CLUB and ELITE oarsmen.

The detraining and retraining of an elite rower: a case study

A heavyweight male rower, and current Olympic champion, undertook a laboratory-based incremental rowing test on four separate occasions; eight weeks prior to the Sydney Olympics (Pre OG), after eight weeks of inactivity (Post-IA), after 8 weeks of retraining (Post 8) and after a further 12 weeks of training (Post 20). Following the period of inactivity, peak oxygen uptake (VO2peak) declined by 8%, power at reference blood lactate concentrations declined by approximately 100 W (25%), and power at VO2peak was 20% lower. With eight weeks of retraining, rapid improvements were seen. For most parameters, however, the rate of improvement slowed and after 20 weeks of retraining the individual was approaching pre-Olympic levels. VO2 at lactate threshold as a percentage of VO2peak remained unchanged. These results show that detraining in the elite athlete can be pronounced, with rapid improvements upon retraining which slow, so that retraining takes considerably longer to achieve than detraining did. Complete cessation of training should be limited to short periods only in the preparation of the elite heavyweight rower. Any break should, if possible, include 'maintenance training'. In this way any decrements in those physiological parameters associated with 2000 m rowing performance will be minimised.

Determinants of 2,000 m rowing ergometer performance in elite rowers

This study examined the physiological determinants of performance during rowing over 2,000 m on an ergometer in finalists from World Championship rowing or sculling competitions from all categories of competion rowing (19 male and 13 female heavyweight, 4 male and 5 female lightweight). Discontinuous incremental rowing to exhaustion established the blood lactate threshold, maximum oxygen consumption (VO(2max)) and power at VO(2max); five maximal strokes assessed maximal force, maximal power and stroke length. These results were compared to maximal speed during a 2,000 m ergometer time trial. The strongest correlations were for power at VO(2max), maximal power and maximal force (r=0.95; P<0.001). Correlations were also observed for VO(2max) (r=0.88, P<0.001) and oxygen consumption (VO(2)) at the blood lactate threshold (r=0.87, P=0.001). The physiological variables were included in a stepwise regression analysis to predict performance speed (metres per second). The resultant model included power at VO(2max), VO(2) at the blood lactate threshold, power at the 4 mmol x l(-1) concentration of blood lactate and maximal power which together explained 98% of the variance in the rowing performance over 2,000 m on an ergometer. The model was validated in 18 elite rowers, producing limits of agreement from -0.006 to 0.098 m x s(-1) for speed of rowing over 2,000 m on the ergometer, equivalent to times of -1.5 to 6.9 s (-0.41% to 1.85%). Together, power at VO(2max), VO(2) at the blood lactate threshold, power at 4 mmol x l(-1) blood lactate concentration and maximal power could be used to predict rowing performance.