The Effects of Different Training Backgrounds on VO2 Responses to All-Out and Supramaximal Constant-Velocity Running Bouts

To investigate the impact of different training backgrounds on pulmonary oxygen uptake (V̇O₂) responses during all-out and supramaximal constant-velocity running exercises, nine sprinters (SPRs) and eight endurance runners (ENDs) performed an incremental test for maximal aerobic velocity (MAV) assessment and two supramaximal running exercises (1-min all-out test and constant-velocity exercise). The V̇O₂ responses were continuously determined during the tests (K4^b2, Cosmed, Italy). A mono-exponential function was used to describe the V̇O₂ onset kinetics during constant-velocity test at 110%MAV, while during 1-min all-out test the peak of V̇O₂ (V̇O₂peak), the time to achieve the V̇O₂peak (tV̇O₂peak) and the V̇O₂ decrease at last of the test was determined to characterize the V̇O₂ response. During constant-velocity exercise, ENDs had a faster V̇O₂ kinetics than SPRs (12.7 ± 3.0 vs. 19.3 ± 5.6 s; p < 0.001). During the 1-min all-out test, ENDs presented slower tV̇O₂peak than SPRs (40.6 ± 6.8 and 28.8 ± 6.4 s, respectively; p = 0.002) and had a similar V̇O₂peak relative to the V̇O₂max (88 ± 8 and 83 ± 6%, respectively; p = 0.157). Finally, SPRs was the only group that presented a V̇O₂ decrease in the last half of the test (-1.8 ± 2.3 and 3.5 ± 2.3 ml.kg^-1.min^-1, respectively; p < 0.001). In summary, SPRs have a faster V̇O₂ response when maximum intensity is required and a high maximum intensity during all-out running exercise seems to lead to a higher decrease in V̇O₂ in the last part of the exercise.     

Deletion of CD73 increases exercise power in mice

Ecto-5′-nucleotidase or CD73 is the main source of extracellular adenosine involved in the activation of adenosine A_2A receptors, responsible for the ergogenic effects of caffeine. We now investigated the role of CD73 in exercise by comparing female wild-type (WT) and CD73 knockout (KO) mice in a treadmill-graded test to evaluate running power, oxygen uptake (V̇O₂), and respiratory exchange ratio (RER) — the gold standards characterizing physical performance. Spontaneous locomotion in the open field and submaximal running power and V̇O₂ in the treadmill were similar between CD73-KO and WT mice; V̇O₂max also demonstrated equivalent aerobic power, but CD73-KO mice displayed a 43.7 ± 4.2% larger critical power (large effect size, P < 0.05) and 3.8 ± 0.4% increase of maximum RER (small effect size, P < 0.05). Thus, KO of CD73 was ergogenic; i.e., it increased physical performance.     

Effects of self-paced high-intensity interval training and moderate-intensity continuous training on the physical performance and psychophysiological responses in recreationally active young adults

This study aimed to compare the effects of 8-week self-paced high-intensity interval training (HIIT) vs. self-paced moderate-intensity continuous training (MICT) on the physical performance and psychophysiological responses of young adults. Twenty-eight recreationally active young adults (age: 21.1 ± 1.6 years) were randomly assigned to either the self-paced HIIT (n = 14) or the MICT (n = 14) group training protocol. The HIIT consisted of two 12–24 x 30 seconds of high-intensity runs interspersed by 30 seconds of recovery. The MICT completed 24–48 minutes of continuous running. Before and after the 8-week interventions the following tests were completed: maximum oxygen consumption (V̇O_2max) estimated from the Yo-Yo Intermittent Recovery Test level 1 (YYIRTL-1), repeated sprint ability (RSA), 10–30-m sprint test, change of direction test (T-drill), countermovement jump (CMJ) and squat jump (SJ), and triple hop distance test (THD). Training rating of perceived exertion (RPE) and physical activity enjoyment scale (PACES) were assessed during the training programme. The HIIT resulted in greater improvement in YYIRTL-1, V̇O_2max, RSA and T-drill performances compared to the MICT. Furthermore, RPE and PACES values were higher in the HIIT than the MICT. This study suggested that self-paced HIIT may be a more effective training regime to improve aerobic fitness with greater physical enjoyment in recreationally active young adults.     

Effects of Heavy Strength Training on Running Performance and Determinants of Running Performance in Female Endurance Athletes

Purpose

The purpose of the current study was to investigate the effects of adding strength training to normal endurance training on running performance and running economy in well-trained female athletes. We hypothesized that the added strength training would improve performance and running economy through altered stiffness of the muscle-tendon complex of leg extensors.

Methods

Nineteen female endurance athletes [maximal oxygen consumption (VO_2max): 53±3 ml∙kg^-1∙min^-1, 5.8 h weekly endurance training] were randomly assigned to either normal endurance training (E, n = 8) or normal endurance training combined with strength training (E+S, n = 11). The strength training consisted of four leg exercises [3 x 4–10 repetition maximum (RM)], twice a week for 11 weeks. Muscle strength, 40 min all-out running distance, running performance determinants and patellar tendon stiffness were measured before and after the intervention.

Results

E+S increased 1RM in leg exercises (40 ± 15%) and maximal jumping height in counter movement jump (6 ± 6%) and squat jump (9 ± 7%, p < 0.05). This was accompanied by increased muscle fiber cross sectional area of both fiber type I (13 ± 7%) and fiber type II (31 ± 20%) in m. vastus lateralis (p < 0.05), with no change in capillary density in m. vastus lateralis or the stiffness of the patellar tendon. Neither E+S nor E changed running economy, fractional utilization of VO_2max or VO_2max. There were also no change in running distance during a 40 min all-out running test in neither of the groups.

Conclusion

Adding heavy strength training to endurance training did not affect 40 min all-out running performance or running economy compared to endurance training only.     

Maximal oxygen uptake, anaerobic threshold and running economy in women and men with similar performances level in marathons

Sex differences in running economy (gross oxygen cost of running, C_R), maximal oxygen uptake (VO_2max), anaerobic threshold (Th_an), percentage utilization of aerobic power (% VO_2max), and Th_an during running were investigated. There were six men and six women aged 20–30 years with a performance time of 2 h 40 min over the marathon distance. The VO_2max, Th_an, and CR were measured during controlled running on a treadmill at 1° and 3° gradient. From each subject's recorded time of running in the marathon, the average speed (v _M) was calculated and maintained during the treadmill running for 11 min. The VO_{2 max} was inversely related to body mass (m _b), there were no sex differences, and the mean values of the reduced exponent were 0.65 for women and 0.81 for men. These results indicate that for running the unit ml·kg^–0.75·min^–1 is convenient when comparing individuals with different m _b. The VO_2max was about 10% (23 ml·kg^–0.75·min^–1) higher in the men than in the women. The women had on the average 10–12 ml·kg^–0.75·min^–1 lower VO₂ than the men when running at comparable velocities. Disregarding sex, the mean value of C_R was 0.211 (SEM 0.005) ml·kg^–1·m^–1 (resting included), and was independent of treadmill speed. No sex differences in Th_an expressed as % VO_2max or percentage maximal heart rate were found, but Than expressed as VO₂ in ml·kg^–0.75·min^–1 was significantly higher in the men compared to the women. The percentage utilization of f _emax and concentration of blood lactate at v _M was higher for the female runners. The women ran 2 days more each week than the men over the first 4 months during the half year preceding the marathon race. It was concluded that the higher VO_2max and Th_an in the men was compensated for by more running, superior C_R, and a higher exercise intensity during the race in the performance-matched female marathon runners.     

A comparison of two commercially available ELISA methods for the quantification of human plasma heat shock protein 70 during rest and exercise stress

This study compared resting and exercise heat/hypoxic stress-induced levels of plasma extracellular heat shock protein 70 (eHSP70) in humans using two commercially available enzyme-linked immunosorbent assay (ELIS)A kits. EDTA plasma samples were collected from 21 males during two separate investigations. Participants in part A completed a 60-min treadmill run in the heat (HOT70; 33.0 ± 0.1 °C, 28.7 ± 0.8 %, n = 6) at 70 % V̇O_2max. Participants in part B completed 60 min of cycling exercise at 50 % V̇O_2max in either hot (HOT50; 40.5 °C, 25.4 relative humidity (RH)%, n = 7) or hypoxic (HYP50; fraction of inspired oxygen (F_IO₂) = 0.14, 21 °C, 35 % RH, n = 8) conditions. Samples were collected prior to and immediately upon termination of exercise and analysed for eHSP70 using EKS-715 high-sensitivity HSP70 ELISA and new ENZ-KIT-101 Amp’d™ HSP70 high-sensitivity ELISA. ENZ-KIT was superior in detecting resting eHSP70 (1.54 ± 3.27 ng·mL⁻¹; range 0.08 to 14.01 ng·mL⁻¹), with concentrations obtained from 100 % of samples compared to 19 % with EKS-715 assay. The ENZ-KIT requires optimisation prior to running samples in order to ensure participants fall within the standard curve, a step not required with EKS-715. Using ENZ-KIT, a 1:4 dilution allowed for quantification of resting HSP70 in 26/32 samples, with a 1:8 (n = 3) and 1:16 (n = 3) dilution required to determine the remaining samples. After exercise, eHSP70 was detected in 6/21 and 21/21 samples using EKS-715 and ENZ-KIT, respectively. eHSP70 was increased from rest after HOT70 (p < 0.05), but not HOT50 (p > 0.05) or HYP50 (p > 0.05) when analysed using ENZ-KIT. It is recommended that future studies requiring the precise determination of resting plasma eHSP70 use the ENZ-KIT (i.e. HSP70 Amp’d® ELISA) instead of the EKS-715 assay, despite additional assay development time and cost required.     

Skeletal muscle biochemical origin of exercise intensity domains and their relation to whole-body V̇O2 kinetics

This article presents the biochemical intra-skeletal-muscle basis of exercise intensity domains: moderate (M), heavy (H), very heavy (VH) and severe (S). Threshold origins are mediated by a ‘P_i double-threshold’ mechanism of muscle fatigue, which assumes (1) additional ATP usage, underlying muscle V̇O₂ and metabolite slow components, is initiated when inorganic phosphate (P_i) exceeds a critical value (Pi_crit); (2) exercise is terminated because of fatigue, when P_i reaches a peak value (Pi_peak); and (3) the P_i increase and additional ATP usage increase mutually stimulate each other forming a positive feedback. M/H and H/VH borders are defined by P_i on-kinetics in relation to Pi_crit and Pi_peak. The values of the ATP usage activity, proportional to power output (PO), for the M/H, H/VH and VH/S borders are lowest in untrained muscle and highest in well-trained muscle. The metabolic range between the M/H and H/VH border (or ‘H space’) decreases with muscle training, while the difference between the H/VH and VH/S border (or ‘VH space’) is only weakly dependent on training status. The absolute magnitude of the muscle V̇O₂ slow-component, absent in M exercise, rises gradually with PO to a maximal value in H exercise, and then decreases with PO in VH and S exercise. Simulations of untrained, physically active and well-trained muscle demonstrate that the muscle M/H border need not be identical to the whole-body M/H border determined from pulmonary V̇O₂ on-kinetics and blood lactate, while suggesting that the biochemical origins of the H/VH border reside within skeletal muscle and correspond to whole-body critical power.     

DIFFERENCES IN GROUND CONTACT TIME EXPLAIN THE LESS EFFICIENT RUNNING ECONOMY IN NORTH AFRICAN RUNNERS

The purpose of this study was to investigate the relationship between biomechanical variables and running economy in North African and European runners. Eight North African and 13 European male runners of the same athletic level ran 4-minute stages on a treadmill at varying set velocities. During the test, biomechanical variables such as ground contact time, swing time, stride length, stride frequency, stride angle and the different sub-phases of ground contact were recorded using an optical measurement system. Additionally, oxygen uptake was measured to calculate running economy. The European runners were more economical than the North African runners at 19.5 km · h⁻¹, presented lower ground contact time at 18 km · h⁻¹ and 19.5 km · h⁻¹ and experienced later propulsion sub-phase at 10.5 km · h⁻¹,12 km · h⁻¹, 15 km · h⁻¹, 16.5 km · h⁻¹ and 19.5 km · h⁻¹ than the European runners (P < 0.05). Running economy at 19.5 km · h⁻¹ was negatively correlated with swing time (r = -0.53) and stride angle (r = -0.52), whereas it was positively correlated with ground contact time (r = 0.53). Within the constraints of extrapolating these findings, the less efficient running economy in North African runners may imply that their outstanding performance at international athletic events appears not to be linked to running efficiency. Further, the differences in metabolic demand seem to be associated with differing biomechanical characteristics during ground contact, including longer contact times.     

Better economy in field running than on the treadmill: evidence from high-level distance runners

Given the ongoing interest in ways to improve the specificity of testing elite athletes in their natural environment, portable metabolic systems provide an opportunity to assess metabolic demand of exercise in sport-specific settings. Running economy (RE) and maximal oxygen uptake (V.O₂max) were compared between track and treadmill (1% inclination) conditions in competitive level European distance runners who were fully habituated to treadmill running (n = 13). All runners performed an exercise test on running track and on treadmill. While V.O₂max was similar on the track and on the treadmill (68.5 ± 5.3 vs. 71.4 ± 6.4 ml·kg⁻¹·min⁻¹, p = 0.105, respectively), superior RE was found on the track compared to the treadmill (215.4 ± 12.4 vs. 236.8 ± 18.0 O₂ ml·kg⁻¹·km⁻¹, p < 0.001). RE on the track was strongly correlated with RE on the treadmill (r = 0.719, p = 0.006). The present findings indicate that high-level distance runners have significantly better RE but not V.O₂max on the track compared to treadmill. This difference may be due to biomechanical adjustments. As RE is strongly correlated between the two conditions, it would be reasonable to assume that interventions affecting RE on the treadmill will also affect RE on the track.     

Assessment of middle-distance running performance in sub-elite young runners using energy cost of running

The purpose of this study was to assess the validity of v _amax as an indicator of middle-distance running performance in sub-elite young runners, _amax being defined as the quotient maximal oxygen uptake (V˙O _2max) divided by the net energy cost of running (C _r) on a treadmill at a submaximal running velocity (280 m · min⁻¹). The V˙O _2max, ventilatory threshold, _amax, and C _r were assessed in 39 young male sub-elite runners having only small variations in performance level. The relationship between each variable and running performance (at 1500 m, 3000 m, and 5000 m) was evaluated. A trend toward a negative correlation existed between C _r and performance although this was not significant. The V˙O _2max and _amax were significantly related to performance. The _amax accounted for around 50% of the variability in performance whereas other physiological variables selected in this study were responsible, at best, for approximately 39%. The results presented in this study suggested that _amax was a useful indicator of middle-distance running performance in sub-elite young runners with similar performance levels as well as in top elite athletes. Accepted: 19 August 1997     

Long Distance Runners Present Upregulated Sweating Responses than Sedentary Counterparts

Relatively few studies have investigated peripheral sweating mechanisms of long-distance runners. The aim of this study was to compare peripheral sweating mechanisms in male long-distance runners, and sedentary counterparts. Thirty six subjects, including 20 sedentary controls and 16 long-distance runners (with 7–12 years of athletic training, average 9.2±2.1 years) were observed. Quantitative sudomotor axon reflex testing (QSART) with iontophoresis (2 mA for 5 min) and 10% acetylcholine (ACh) were performed to determine axon reflex-mediated and directly activated (DIR, muscarinic receptor) sweating. Sweat onset time, sweat rate, number of activated sweat glands, sweat output per gland and skin temperature were measured at rest while maximum oxygen uptake (VO₂max) were measured during maximal cycling. Sweat rate, activated sweat glands, sweat output per gland, skin temperature and VO₂max were significantly higher in the trained runners than in the sedentary controls. Sweat onset time was significantly shorter for the runners. In the group of long-distance runners, significant correlations were found between VO₂max and sweat onset time (r² = 0.543, P<0.01, n = 16), DIR sweat rate (r² = 0.584, P<0.001, n = 16), sweat output per gland (r² = 0.539, P<0.01, n = 16). There was no correlation between VO₂max and activated sweat glands. These findings suggest that habitual long-distance running results in upregulation of the peripheral sweating mechanisms in humans. Additional research is needed to determine the molecular mechanism underlying these changes. These findings complement the existing sweating data in long-distance runners.     

Markers for Routine Assessment of Fatigue and Recovery in Male and Female Team Sport Athletes during High-Intensity Interval Training

Aim

Our study aimed to investigate changes of different markers for routine assessment of fatigue and recovery in response to high-intensity interval training (HIIT).

Methods

22 well-trained male and female team sport athletes (age, 23.0 ± 2.7 years; V̇O_2max, 57.6 ± 8.6 mL·min·kg⁻¹) participated in a six-day running-based HIIT-microcycle with a total of eleven HIIT sessions. Repeated sprint ability (RSA; criterion measure of fatigue and recovery), countermovement jump (CMJ) height, jump efficiency in a multiple rebound jump test (MRJ), 20-m sprint performance, muscle contractile properties, serum concentrations of creatinkinase (CK), c-reactive protein (CRP) and urea as well as perceived muscle soreness (DOMS) were measured pre and post the training program as well as after 72 h of recovery.

Results

Following the microcycle significant changes (p < 0.05) in RSA as well as in CMJ and MRJ performance could be observed, showing a decline (%Δ ± 90% confidence limits, ES = effect size; RSA: -3.8 ± 1.0, ES = -1.51; CMJ: 8.4 ± 2.9, ES = -1.35; MRJ: 17.4 ± 4.5, ES = -1.60) and a return to baseline level (RSA: 2.8 ± 2.6, ES = 0.53; CMJ: 4.1 ± 2.9, ES = 0.68; MRJ: 6.5 ± 4.5, ES = 0.63) after 72 h of recovery. Athletes also demonstrated significant changes (p < 0.05) in muscle contractile properties, CK, and DOMS following the training program and after the recovery period. In contrast, CRP and urea remained unchanged throughout the study. Further analysis revealed that the accuracy of markers for assessment of fatigue and recovery in comparison to RSA derived from a contingency table was insufficient. Multiple regression analysis also showed no correlations between changes in RSA and any of the markers.

Conclusions

Mean changes in measures of neuromuscular function, CK and DOMS are related to HIIT induced fatigue and subsequent recovery. However, low accuracy of a single or combined use of these markers requires the verification of their applicability on an individual basis.     

DIFFERENT ENDURANCE CHARACTERISTICS OF FEMALE AND MALE GERMAN SOCCER PLAYERS

The aims of the present study were to assess gender differences regarding lactate threshold and intermittent shuttle run performance in female and male soccer players as well as to investigate the relationships between both endurance characteristics in both genders. Fourteen female (1^st division) and thirteen male (4^th division) soccer players completed an incremental test (IT) to determine running velocities at 2 and 4 mmol · l⁻¹ blood lactate (v2 and v4) and maximum velocity (v_max) as well as an interval shuttle run test (ISRT) to determine running distance. Based on v2 and v4 and their percentages in relation to v_max, three intensity zones were calculated: a low lactate zone (<v2), a lactate accommodation zone (v2 to v4), and a lactate accumulation zone (>v4). Female soccer players have a lower v4 (8.2%), v_max (11.3%) and ISRT distance (31.6%). No gender difference was found in v2. In contrast to males, ISRT distance correlates with v_max as well as with v2 and v4 in female soccer players. The intensity zones <v2 and >v4 differ between genders. The present study revealed that gender differences increase when the running performance is intermittent including change of directions. In both genders, different relationships between lactate threshold and intermittent shuttle run performance exist. During incremental testing, the running performances of female and male players reflect different distributions of aerobic and anaerobic metabolic pathways. The revealed gender differences should be considered for soccer endurance training.     

Comparison of “Live High-Train Low” in Normobaric versus Hypobaric Hypoxia

We investigated the changes in both performance and selected physiological parameters following a Live High-Train Low (LHTL) altitude camp in either normobaric hypoxia (NH) or hypobaric hypoxia (HH) replicating current “real” practices of endurance athletes. Well-trained triathletes were split into two groups (NH, n = 14 and HH, n = 13) and completed an 18-d LHTL camp during which they trained at 1100–1200 m and resided at an altitude of 2250 m (P_iO₂  = 121.7±1.2 vs. 121.4±0.9 mmHg) under either NH (hypoxic chamber; F_iO₂ 15.8±0.8%) or HH (real altitude; barometric pressure 580±23 mmHg) conditions. Oxygen saturations (S_pO₂) were recorded continuously daily overnight. P_iO₂ and training loads were matched daily. Before (Pre-) and 1 day after (Post-) LHTL, blood samples, VO_2max, and total haemoglobin mass (Hb_mass) were measured. A 3-km running test was performed near sea level twice before, and 1, 7, and 21 days following LHTL. During LHTL, hypoxic exposure was lower for the NH group than for the HH group (220 vs. 300 h; P<0.001). Night S_pO₂ was higher (92.1±0.3 vs. 90.9±0.3%, P<0.001), and breathing frequency was lower in the NH group compared with the HH group (13.9±2.1 vs. 15.5±1.5 breath.min⁻¹, P<0.05). Immediately following LHTL, similar increases in VO_2max (6.1±6.8 vs. 5.2±4.8%) and Hb_mass (2.6±1.9 vs. 3.4±2.1%) were observed in NH and HH groups, respectively, while 3-km performance was not improved. However, 21 days following the LHTL intervention, 3-km run time was significantly faster in the HH (3.3±3.6%; P<0.05) versus the NH (1.2±2.9%; ns) group. In conclusion, the greater degree of race performance enhancement by day 21 after an 18-d LHTL camp in the HH group was likely induced by a larger hypoxic dose. However, one cannot rule out other factors including differences in sleeping desaturations and breathing patterns, thus suggesting higher hypoxic stimuli in the HH group.     

Mechanisms of Attenuation of Pulmonary V’O2 Slow Component in Humans after Prolonged Endurance Training

In this study we have examined the effect of prolonged endurance training program on the pulmonary oxygen uptake (V’O₂) kinetics during heavy-intensity cycling-exercise and its impact on maximal cycling and running performance. Twelve healthy, physically active men (mean±SD: age 22.33±1.44 years, V’O_2peak 3198±458 mL ∙ min^-1) performed an endurance training composed mainly of moderate-intensity cycling, lasting 20 weeks. Training resulted in a decrease (by ~5%, P = 0.027) in V’O₂ during prior low-intensity exercise (20 W) and in shortening of τ_p of the V’O₂ on-kinetics (30.1±5.9 s vs. 25.4±1.5 s, P = 0.007) during subsequent heavy-intensity cycling. This was accompanied by a decrease of the slow component of V’O₂ on-kinetics by 49% (P = 0.001) and a decrease in the end-exercise V’O₂ by ~5% (P = 0.005). An increase (P = 0.02) in the vascular endothelial growth factor receptor 2 mRNA level and a tendency (P = 0.06) to higher capillary-to-fiber ratio in the vastus lateralis muscle were found after training (n = 11). No significant effect of training on the V’O_2peak was found (P = 0.12). However, the power output reached at the lactate threshold increased by 19% (P = 0.01). The power output obtained at the V’O_2peak increased by 14% (P = 0.003) and the time of 1,500-m performance decreased by 5% (P = 0.001). Computer modeling of the skeletal muscle bioenergetic system suggests that the training-induced decrease in the slow component of V’O₂ on-kinetics found in the present study is mainly caused by two factors: an intensification of the each-step activation (ESA) of oxidative phosphorylation (OXPHOS) complexes after training and decrease in the ‘‘additional” ATP usage rising gradually during heavy-intensity exercise.     

Influence of the oxygen uptake slow component on the aerobic energy cost of high-intensity submaximal treadmill running in humans

During high-intensity running, the oxygen uptake (V˙O₂) kinetics is characterised by a slow component which delays the attainment of the steady-state beyond the 3rd min of exercise. To assess if the aerobic energy cost of running measured at the 3rd min (C ₃) adequately reflects the variability of the true aerobic energy cost measured during the steady-state (C _ss), 13 highly-trained runners completed sessions of square-wave running at intensities above 80% maximal oxygen uptake (V˙O_2max) on a level treadmill. To evaluate the time at which the steady-state V˙O₂ was attained (t _ss), the V˙O₂ responses were described using a general double-exponential equation and t _ss was defined as the time at which V˙O₂ was less than 1% below the asymptotic value given by the model. All the subjects achieved a steady state for intensities equal to or greater than 92% V˙O_2max, and 8 out of 13 achieved it at 99% V˙O_2max. In all cases, t _ss was less than 13 min. For intensities greater than 85% V˙O_2max, C _ss was significantly higher than C ₃ and was positively related to %V˙O_2max (r= 0.44; P < 0.001) while C ₃ remained constant. The C ₃ only explained moderately the variability of C _ss (0.39 < r ² < 0.72, depending on the velocity or the (relative intensity at which the relationship was calculated). Moreover, the excess aerobic energy cost of running the (difference between C _ss and C ₃) was well predicted by age (0.90 < r ² < 0.93). Therefore, when the aerobic profile of runners is evaluated, it is recommended that their running efficiencies at velocities which reflect their race intensities should be determined, with V˙O₂ data being measured at the true steady-state. Accepted: 1 June 1998     

Running for Exercise Mitigates Age-Related Deterioration of Walking Economy

Introduction

Impaired walking performance is a key predictor of morbidity among older adults. A distinctive characteristic of impaired walking performance among older adults is a greater metabolic cost (worse economy) compared to young adults. However, older adults who consistently run have been shown to retain a similar running economy as young runners. Unfortunately, those running studies did not measure the metabolic cost of walking. Thus, it is unclear if running exercise can prevent the deterioration of walking economy.

Purpose

To determine if and how regular walking vs. running exercise affects the economy of locomotion in older adults.

Methods

15 older adults (69±3 years) who walk ≥30 min, 3x/week for exercise, “walkers” and 15 older adults (69±5 years) who run ≥30 min, 3x/week, “runners” walked on a force-instrumented treadmill at three speeds (0.75, 1.25, and 1.75 m/s). We determined walking economy using expired gas analysis and walking mechanics via ground reaction forces during the last 2 minutes of each 5 minute trial. We compared walking economy between the two groups and to non-aerobically trained young and older adults from a prior study.

Results

Older runners had a 7–10% better walking economy than older walkers over the range of speeds tested (p = .016) and had walking economy similar to young sedentary adults over a similar range of speeds (p = .237). We found no substantial biomechanical differences between older walkers and runners. In contrast to older runners, older walkers had similar walking economy as older sedentary adults (p = .461) and ∼26% worse walking economy than young adults (p<.0001).

Conclusion

Running mitigates the age-related deterioration of walking economy whereas walking for exercise appears to have minimal effect on the age-related deterioration in walking economy.     

Times to exhaustion at 100% of velocity at [(V)\dot]\textO\text2 \dot V{\text{O}}_{\text{2}} max and modelling of the time-limit / velocity relationship in elite long-distance runners

The aim of this study was to measure running times to exhaustion (Tlim) on a treadmill at 100% of the minimum velocity which elicits _{max max} in 38 elite male long - distance runners _max = 71.4 ± 5.5 ml.kg^–1.min^–1 and _max = 21.8 ± 1.2 km.h^–1). The lactate threshold (LT) was defined as a starting point of accelerated lactate accumulation around 4 mM and was expressed in _max. Tlim value was negatively correlated with _max (r = -0.362, p< 0.05) and _max (r = –0.347, p< 0.05) but positively with LT (%v _max) (r = 0.378, p < 0.05). These data demonstrate that running time to exhaustion at _max in a homogeneous group of elite male long-distance runners was inversely related to _max and experimentally illustrates the model of Monod and Scherrer regarding the time limit-velocity relationship adapted from local exercise for running by Hughson et al. (1984) .