How parameters derived from oxygen uptake kinetics relate to critical speed is not fully understood, and how such parameters relate to more sport-specific performances, such as shuttle running, has not been investigated. Therefore, the primary aims of the present student were to examine the kinetics during all-out linear and shuttle running and compare physiological variables of all-out running to variables measured during a graded exercise test (GXT). Fifteen male soccer players performed a graded exercise test (GXT) and the kinetics from a series of three different 3-min all-out tests (3MT’s) were evaluated. achieved during the GXT did not differ from maximal achieved during the all-out tests (F = 1.85, p = 0.13) (overall ICC = 0.65; typical error = 2.48 ml∙kg^-1∙min^-1; coefficient of variation = 4.8%). A moderate, inverse correlation (r = -0.62, p = 0.02) was observed between τ (14.7 ± 1.92 s) and CS (3.96 ± 0.52 m∙s^-1) despite the narrow SD for τ. No differences (p > 0.05) were observed for any of the kinetics between continuous and shuttle running bouts. The linear running 3MT (r3MT) represents a viable surrogate to the GXT and data beyond CS and D’ may be gleaned by using the bi-exponential speed-time model.

All‐out exercise testing (AOT) has emerged as a method for quantifying critical speed (CS) and the curvature constant (D′). The AOT method was recently validated for shuttle running yet how that method compares with linear running is unknown. In the present study, we utilized a novel bi‐exponential model that derives CS and D′ with additional new parameters from the AOT method. Fourteen male athletes (age = 21.6 ± 2.2 years; height = 177 ± 70 cm; weight = 83.0 ± 11.8 kg) completed a graded exercise test (GXT) to derive maximum oxygen uptake () and the average speed between gas exchange threshold and (sΔ50%), a linear AOT, and two shuttle AOTs. Measurement agreement was determined using intraclass correlation coefficient (ICC ), typical error (TE), and coefficient of variation (CV). The y‐asymptote () of the speed‐time curve (3.52 ± 0.66 m·sec⁻¹) did not differ from sΔ50% (3.49 ± 0.41 m·sec⁻¹) or CS (3.77 ± 0.56 m·sec⁻¹) (P = 0.34). Strong agreement was observed for estimates of CS (ICC = 0.92, TE = 0.18 m·sec⁻¹, and CV = 5.7%) and D′ (ICC = 0.94, TE = 16.0 m, CV = 7.6%) with significant (P < 0.01) correlations observed between and CS and between and (r values of 0.74 and 0.84, respectively). The time constant of the decay in speed () and the amplitude between maximal speed and () emerged as unique metrics. The and metrics may glean new insights for prescribing and interpreting high‐intensity exercise using the AOT method.

Kramer, M, Clark, IE, Jamnick, N, Strom, C, and Pettitt, RW. Normative data for critical speed and D' for high-level male rugby players. J Strength Cond Res 32(3): 783–789, 2018—The critical speed (CS) concept helps characterize the aerobic and anaerobic fitness of an athlete. Rugby players should, hypothetically, have modest CS values but extremely high curvature constant (D') values, yet, normative data are currently unavailable. To develop normative data of CS and D' for high-level male rugby players, a total of 30 male rugby players were recruited from the Eastern Cape of South Africa. All subjects performed the running 3-minute all-out exercise test (3 MT) using global positioning system (GPS) technology to determine CS and D'. The GPS data were used to determine the total distance and velocities performed, and to examine for pacing effects. Summary statistics of mean ± SD are provided. High total running speeds for the initial 150 seconds (S _150s = 5.79 ± 0.59 m·s⁻¹), and total distance (3 MT distance = 871.5 ± 71.9 m) were observed. A total of 13 of 30 subjects surpassed the 300 m D' value (mean D' = 288.2 ± 49.1 m). The CS of the total group was 3.87 ± 0.55 m·s⁻¹. All 3 MT-derived data were categorized using standard nine (stanine) tables that allowed for the generation of normative data with which future performances, performances across similar sporting domains, and more accurate contrasts across the literature can be compared. Skewing of CS and D' was observed between forwards and backs, therefore, between-group differences in neither CS nor D' were observed (p > 0.05). Comparisons with previous literature indicate that male rugby players have higher CS values than female rugby players. When compared with Olympic distance runners, male rugby players have markedly higher D' values and markedly lower CS values. The 3 MT provides a useful procedure for assessing and prescribing high-intensity interval training for rugby athletes.

Most schoolchildren carry schoolbags, of which a substantial proportion carry loads that exceed 15% of their body mass. Although the effects of loading have been investigated to varying degrees, the status of schoolbag loading and the acute affects thereof on gait and posture have not been thoroughly investigated within the South African context. A total of 60 participants in the 10–13-year age range volunteered for the present study. Significant differences were evident for relative load carriage (χ²(3) = 14.54, p < 0.001), forefoot and heel forces (M_diff = 17.05–34.86 N, p < 0.001), force ratios (M_diff = 0.02, p = 0.029), and gait speed (M_diff = −0.18 km/hr, p = 0.016), but not for any postural angles (M_diff = −3.37–6.08 deg, all p > 0.052). Those who exceeded 15% BM were ~9 times more likely to report pain than those below 15% BM. The children in the current study carried significantly heavier relative loads (p < 0.001) compared to similarly aged children from other countries. Loading leads to acute changes in posture and gait that are likely not meaningful. However, excessive loading (>15% BM) leads to significantly higher perceptions and reporting of pain in 10–13-year-old children.