Physiological and Perceptual Demands of Running on a Curved Nonmotorized Treadmill Compared With Running on a Motorized Treadmill Set at Different Grades.

Schoenmakers, PPJM, Crisell, JJ, and Reed, KE. Physiological and perceptual demands of running on a curved nonmotorized treadmill compared with running on a motorized treadmill set at different grades. J Strength Cond Res 34(5): 1197-1200, 2020-The current study compared the physiological and perceptual demands of running on a commercially available curved nonmotorized treadmill (cNMT) with different incline grades on a motorized treadmill (MT). Ten male team-sport athletes completed, after a familiarization session, a 6-minute run at a target velocity of 2.78 m·s on the cNMT (cNMTrun). The mean individual running velocity of cNMTrun was then used as warm-up and experimental running velocity in 3 subsequent visits, in which subjects ran for 6 minutes on the MT set at different grades (4, 6, or 8%). In all experimental trials (cNMTrun, 4MTrun, 6MTrun, and 8MTrun) and in the warm-up of the subjects' third visit (1MTrun), oxygen consumption (V[Combining Dot Above]O2) and heart rate (HR) were monitored, and ratings of perceived exertion (RPE) were obtained. The HR in cNMTrun was significantly higher compared with all MT trials. V[Combining Dot Above]O2 and RPE were significantly higher in cNMTrun compared with 1MTrun and 4MTrun, but not different from 6MTrun and 8MTrun. The relationship between V[Combining Dot Above]O2 and MT grades was highly linear (V[Combining Dot Above]O2 = 34.36 + 1.7 MT grade; r = 0.99), and using linear interpolation, the concave curved design of the cNMT was estimated to mimic a 6.9 ± 3% MT grade. On matched running velocities, V[Combining Dot Above]O2 and RPE responses while running on the cNMT are similar to a 6-8% MT grade. These findings can be used as a reference value by athletes and coaches in the planning of cNMT training sessions and amend running velocities accordingly. Future studies are needed to determine whether this estimate is similar for female runners, or those of a lower body mass.

The effects of recovery duration on physiological and perceptual responses of trained runners during four self-paced HIIT sessions.

OBJECTIVES: This study aimed to examine the effects of different recovery durations on self-selected running velocities, physiological responses, and ratings of perceived exertion (RPE) in a commonly used high intensity interval training (HIIT) protocol. DESIGN & METHODS: Twelve trained runners performed an incremental treadmill exercise test to determine maximal oxygen uptake (V˙O2max) and heart rate (HRmax). In four subsequent visits, participants performed a HIIT session comprising six 4-min work intervals, in which the recovery duration between work intervals equalled either a fixed (1MIN, 2MIN, 3MIN) or a self-selected duration (ssMIN). HIIT sessions were run on a non-motorized treadmill, and were performed under isoeffort conditions. RESULTS: Mean running velocity was significantly higher in 3MIN compared with all other protocols, and higher in ssMIN compared with 2MIN. No significant differences in time spent ≥90% and 95% V˙O2max, or ≥90% and 95% HRmax were evident between the four protocols. RPE responses were similar across and within the protocols showing a gradual increase with each progressive interval. CONCLUSION: In a self-paced HIIT session of six 4-min work intervals, the length of recovery durations had a limited effect on the total physiological strain endured in the training. However, running velocities were higher when participants received the longest recovery period (3MIN). Longer recovery durations may facilitate a higher external training load (faster running), whilst maintaining a similar internal training load (physiological stimulus), and may therefore allow for greater training adaptations.

The Moderating Role of Recovery Durations in High-Intensity Interval-Training Protocols.

Purpose: Over recent years, multiple studies have tried to optimize the exercise intensity and duration of work intervals in high-intensity-interval training (HIIT) protocols. Although an optimal work interval is of major importance to facilitate training adaptations, an optimal HIIT protocol can only be achieved with an adequate recovery interval separating work bouts. Surprisingly, little research has focused on the acute responses and long-term impact of manipulating recovery intervals in HIIT sessions. This invited commentary therefore aimed to review and discuss the current literature and increase the understanding of the moderating role of recovery durations in HIIT protocols. Conclusion: The acute responses to manipulations in recovery durations in repeated-sprint training (RST), sprint interval training (SIT), and aerobic interval training (AIT) protocols have recently begun to receive scientific interest. However, limited studies have manipulated only the recovery duration in RST, SIT, or AIT protocols to analyze the role of recovery durations on long-term training adaptations. In RST and SIT, longer recovery intervals (≥80 s) facilitate higher workloads in subsequent work intervals (compared with short recovery intervals), while potentially lowering the aerobic stimulus of the training session. In AIT, the total physiological strain endured per training protocol appears not to be moderated by the recovery intervals, unless the recovery duration is too short. This invited commentary highlights that further empirical evidence on a variety of RST, SIT, and AIT protocols and in exercise modalities other than cycling is needed.

The physiological and perceptual demands of running on a curved non-motorised treadmill: Implications for self-paced training.

OBJECTIVES: To compare physiological and perceptual response of running on a curved non-motorized treadmill (cNMT) with running on a motorized treadmill (MT), and to determine the running velocity at which a physiological response≥90% V˙O2max was elicited. DESIGN & METHODS: 13 trained male runners (mean±SD; 36±11years, 1.80±0.06m, 70±4kg, V˙O2max: 57.3±3.5 mLkg-1min-1) performed an incremental running test on a MT to determine V˙O2max and the accompanying maximum velocity (Vmax). Participants first completed a familiarization session on the cNMT. Next, participants ran for 4min at five/six progressively higher velocities (40-90% Vmax). These runs were completed on the cNMT and MT in two separate visits in a randomized and counterbalanced order. RESULTS: No participant was able to complete the 4min run at 80% Vmax on the cNMT. Running on the cNMT elicit a higher relative oxygen uptake (%V˙O2max) across all velocities compared to the MT (32.5±5%, p<0.001, ES 3.3±0.9), and was accompanied by significantly higher heart rates (16.8±3%, p<0.001, ES 3.4±1.5), an altered cadence (2.6±0.7%, p<0.001, ES 0.8±0.3) and ratings of perceived exertion (27.2±5%, p<0.001, ES 2.3±0.6). A less efficient running economy was evident when running on the cNMT (+38.4±16%, p<0.001, ES 2.73). Individual (n=9) linear interpolation predicted an exercise intensity of 90% V˙O2max was achieved in the non-motorized condition when running at 62.1±3.5% Vmax (R2=0.986±0.01), which was lower than MT run in which 90% V˙O2max was achieved at 81.4±5.6% Vmax (R2=0.985±0.02; 29.8±8%, p<0.001, ES 3.87). CONCLUSIONS: Running on the cNMT has higher physiological and perceptual demands and increases cadence.

Determining cardiovascular disease risk in elementary school children: developing a healthy heart score.

At least 50% of children have one or more cardiovascular disease (CVD) risk factor. We aimed to 1) determine the prevalence of CVD risk factors in a sample of Canadian children, and 2) create a Healthy Heart Score that could be used in a school setting, to identify children with a greater number and severity of CVD risk factors. Children (n = 242, 122M, 120F, aged 9-11 years) were assessed for cardiovascular fitness, physical activity, systolic/diastolic blood pressure, and body mass index (BMI). Biological values were converted to age and sex specific percentiles and allocated a score. Healthy Heart Scores could range between 5 and 18, with lower scores suggesting a healthier cardiovascular profile. Seventy-seven children volunteered for blood samples in order to assess the relationship between the Healthy Heart Score and (total cholesterol (TC), high and low-density lipoprotein cholesterol (HDL, LDL) and triglycerides (TG). Fifty eight percent of children had elevated scores for at least 1 risk factor. The group mean Healthy Heart Score was 8 (2.2). The mean score was significantly higher in boys (9 (2.2)) compared with girls (8 (2.1), p < 0.01). A high score was significantly associated with a low serum HDL, a high TC:HDL and a high TG concentration. Our results support other studies showing a high prevalence of CVD risk factors in children. Our method of allocation of risk score, according to percentile, allows for creation of an age and sex specific CVD risk profile in children, which takes into account the severity of the elevated risk factor. Key pointsThere was a high incidence of elevated risk factors for cardiovascular disease in Canadian elementary school children.Physical fitness and physical activity levels were particularly low.In this cohort, boys had increased levels of cardiovascular disease risk factors compared with age-matched girls.