Level, Uphill, and Downhill Running Economy Values Are Correlated Except on Steep Slopes

Abstract

The aim of this study was first to determine if level, uphill, and downhill energy cost of running (ECR) values were correlated at different slopes and for different running speeds, and second, to determine the influence of lower limb strength on ECR. Twenty-nine healthy subjects completed a randomized series of 4-min running bouts on an instrumented treadmill to determine their cardiorespiratory and mechanical (i.e., ground reaction forces) responses at different constant speeds (8, 10, 12, and 14 km·h−1) and different slopes (−20, −10, −5, 0, +5, +10, +15, and +20%). The subjects also performed a knee extensor (KE) strength assessment. Oxygen and energy costs of running values were correlated between all slopes by pooling all running speeds (all r2 ≥ 0.27; p ≤ 0.021), except between the steepest uphill vs. level and the steepest downhill slope (i.e., +20% vs. 0% and −20% slopes; both p ≥ 0.214). When pooled across all running speeds, the ECR was inversely correlated with KE isometric maximal torque for the level and downhill running conditions (all r2 ≥ 0.24; p ≤ 0.049) except for the steepest downhill slope (−20%), but not for any uphill slopes. The optimal downhill grade (i.e., lowest oxygen cost) varied between running speeds and ranged from −14% and −20% (all p < 0.001). The present results suggest that compared to level and shallow slopes, on steep slopes ~±20%, running energetics are determined by different factors (i.e., reduced bouncing mechanism, greater muscle strength for negative slopes, and cardiopulmonary fitness for positive slopes). On shallow negative slopes and during level running, ECR is related to KE strength.

The time course of different neuromuscular adaptations to short-term downhill running training and their specific relationships with strength gains

“…From a mechanical point of view, eccentric muscle contraction refers to a muscle action that occurs when the magnitude of the force applied to the muscle exceeds the momentary force produced by the muscle itself, resulting in a lengthening action of the musculotendinous system (Lindstedt et al 2001 ; Douglas et al 2017b ). These unique mechanical properties typically lead to a lower metabolic cost (Abbott et al 1952 ; Fenn 1924 ; Hody et al 2019 ) and lower cardiorespiratory demands (Chasland et al 2017 ; Dufour et al 2004 ; Penailillo et al 2017 ; Lemire et al 2021 ) for a matched workload compared to other contraction modalities, which is of paramount importance in athletic and clinical populations.…”

Correspondence Between Values of Vertical Loading Rate and Oxygen Consumption During Inclined Running

“…The present results confirm that VLR decreases by increasing positive slope but extend the previous work by Gottschall et al [ 19 ] by combining physiological responses to running biomechanics associated with treadmill speed and slope change in a large group of athletes. The results also provide new insights into VLR with respect to ECR in downhill running, which elicits specific cardiorespiratory responses (i.e., lower metabolic demand, more superficial ventilation pattern, exacerbated heart rate) [ 16 , 20 ] relative to level running, whereas it increases VLR, presumably due to increased braking forces to absorb the ground impact itself associated with eccentric muscle actions. The muscles involved during extension forcibly lengthen under the potential effect of gravity to limit the drop-down of the center of mass.…”

“…As indicators of running economy, ECR was normalized by body weight (BW) and averaged over 30 s for each running condition by dividing the mean by the velocity and multiplied by the energy equivalent of O 2 estimated by respiratory exchange ratio to be expressed in J kg −1 m −1 [ 16 ].…”

“…Ground reaction forces in the vertical (VGRF), forward, and lateral components were continuously recorded with an instrumented single-belt treadmill (T170—FMT-MED; Arsalis, Belgium) at a sampling rate of 1000 Hz. The calculation of the various biomechanical parameters has been described previously [ 16 , 17 ]. The VLR was calculated as the average VGRF slope between 20 and 80% of the point where the VGRF slope is less than 15 BW s −1 [ 18 ].…”

Can We Quantify the Benefits of “Super Spikes” in Track Running?

“…The anaerobic metabolic energy contribution is hard to quantify accurately and reliably [ 59 , 60 ], which makes these distances inherently harder to study. While some have tried to quantify the total metabolic energy demand (aerobic and anerobic metabolic energy) by taking into account blood lactate concentrations [ 61 , 62 ], that approach is outdated and ignores the fact that blood lactate concentrations result from the difference in lactate production and lactate utilization [ 60 , 63 ]. This is true irrespective of whether researchers attempt to convert blood lactate concentration to metabolic energy or use it as an intensity outcome by itself.…”