Effect of Level and Downhill Running on Breathing Efficiency

Downhill Running: What Are The Effects and How Can We Adapt? A Narrative Review

Downhill running (DR) is a whole-body exercise model that is used to investigate the physiological consequences of eccentric muscle actions and/or exercise-induced muscle damage (EIMD). In a sporting context, DR sections can be part of running disciplines (off-road and road running) and can accentuate EIMD, leading to a reduction in performance. The purpose of this narrative review is to: (1) better inform on the acute and delayed physiological effects of DR; (2) identify and discuss, using a comprehensive approach, the DR characteristics that affect the physiological responses to DR and their potential interactions; (3) provide the current state of evidence on preventive and in-situ strategies to better adapt to DR. Key findings of this review show that DR may have an impact on exercise performance by altering muscle structure and function due to EIMD. In the majority of studies, EIMD are assessed through isometric maximal voluntary contraction, blood creatine kinase and delayed onset muscle soreness, with DR characteristics (slope, exercise duration, and running speed) acting as the main influencing factors. In previous studies, the median (25th percentile, Q1; 75th percentile, Q3) slope, exercise duration, and running speed were - 12% (- 15%; - 10%), 40 min (30 min; 45 min) and 11.3 km h-1 (9.8 km h-1; 12.9 km h-1), respectively. Regardless of DR characteristics, people the least accustomed to DR generally experienced the most EIMD. There is growing evidence to suggest that preventive strategies that consist of prior exposure to DR are the most effective to better tolerate DR. The effectiveness of in-situ strategies such as lower limb compression garments and specific footwear remains to be confirmed. Our review finally highlights important discrepancies between studies in the assessment of EIMD, DR protocols and populations, which prevent drawing firm conclusions on factors that most influence the response to DR, and adaptive strategies to DR.

Effect of acute downhill running on bone markers in responders and non-responders

This study showed that procollagen type 1 amino-terminal pro-peptide and N-MID osteocalcin significantly increased after exercise independent of the form of muscle contraction. Thus, these preliminary results will be useful for future studies that will consider bone turnover characteristics of responders and non-responders to acute and chronic aerobic exercise.

INTRODUCTION

The aim of the current study was to compare the effects of acute flat running (FR) and downhill running (DHR) on bone turnover markers in men.

METHODS

Fourteen healthy young active men performed three exercise tests in a counterbalanced order, including rest condition, FR, and DHR, at 60% maximal aerobic capacity on a treadmill with 0 and - 12% inclines. Blood samples were taken in the pre-exercise, immediately post-exercise, and 24-h post-exercise periods, and bone markers included total procollagen type 1 amino-terminal pro-peptide (total PINP) and N-MID osteocalcin.

RESULTS

Total P1NP significantly increased after exercise independent of the form of muscle contraction (p > 0.05). N-MID osteocalcin increased after DHR by 17% compared to after pre-exercise, but the difference did not reach significance (p = 0.07; partial eta square, 0.21). Biomarker responses to exercise were dependent on the exercise form and independent of hormone type in half of the participants who were classified as responders. Physiological parameters and changes in muscle voluntary contraction did not explain the differences between responders and non-responders.

CONCLUSION

The effect of acute DHR on bone turnover is determined by biomarker type and participant characteristics. Future studies should discriminate between the characteristics of responders and those of non-responders.

Cardiorespiratory Responses to Downhill Versus Uphill Running in Endurance Athletes

PURPOSE

Mountain running races are becoming increasingly popular, although our understanding of the particular physiology associated with downhill running (DR) in trained athletes remains scarce. This study explored the cardiorespiratory responses to high-slope constant velocity uphill running (UR) and DR.

METHOD

Eight endurance athletes performed a maximal incremental test and 2 15-min running bouts (UR, +15%, or DR, -15%) at the same running velocity (8.5 ± 0.4 km·h^-1). Oxygen uptake ([Formula: see text]O₂), heart rate (HR), and ventilation rates ([Formula: see text]_E) were continuously recorded, and blood lactate (bLa) was measured before and after each trial.

RESULTS

Downhill running induced a more superficial [Formula: see text]_E pattern featuring reduced tidal volume (p < .05, ES = 6.05) but similar respiratory frequency (p > .05, ES = 0.68) despite lower [Formula: see text]_E (p < .05, ES = 5.46), [Formula: see text]O₂ (p < .05, ES = 12.68), HR (p < .05, ES = 6.42), and bLa (p < .05, ES = 1.70). A negative slow component was observed during DR for [Formula: see text]O₂ (p < .05, ES = 1.72) and HR (p < .05, ES = 0.80).

CONCLUSIONS

These results emphasize the cardiorespiratory responses to DR and highlight the need for cautious interpretation of [Formula: see text]O₂, HR, and [Formula: see text]_E patterns as markers of exercise intensity for training load prescription and management.