The magnitude of translational and rotational head accelerations experienced by riders during downhill mountain biking

Objectives To determine the magnitude of translational and rotational head accelerations during downhill mountain biking. Design Observational study Methods Sixteen male downhill cyclists (age 26.4 ± 8.4 years; stature 179.4 ± 7.2 cm; mass 75.3 ± 5.9 kg) were monitored during two rounds of the British Downhill Series. Riders performed two runs on each course wearing a triaxial accelerometer behind the right ear. The means of the two runs for each course were used to determine differences between courses for mean and maximum peak translational (g) and rotational accelerations (rads/s2) and impact duration for each course. Results Significant differences (p 10 g), FW = 12.5 ± 7.6, RYF = 42.8 ± 27.4 (t(22.96) = -4.70; p < 0.001; 95 % CI = 17.00 to 43.64); maximum peak rotational acceleration, FW = 6805.4 ± 3073.8 rads/s2, RYF = 9799.9 ± 3381.7 rads/s2 (t(32) = -2.636; p = 0.01; 95 % CI = 680.31 to 5308.38); mean acceleration duration FW = 4.7 ± 1.2 ms, RYF = 6.5 ± 1.4 ms (t(32) = -4.05; p < 0.001; 95 % CI = 0.91 to 2.76) and maximum acceleration duration, FW = 11.6 ± 4.5 ms, RYF = 21.2 ± 9.1 (t(29.51) = -4.06; p = 0.001; 95 % CI = 4.21 to 14.94). No other significant differences were found. Conclusions Findings indicate that downhill riders may be at risk of sustaining traumatic brain injuries and course design influences the number and magnitude of accelerations

The effect of mountain bike wheel size on Cross-Country performance

The purpose of this study was to determine the influence of different wheel size diameters on indicators of cross-country mountain bike time trial performance. Nine competitive male mountain bikers (age 34.7 ± 10.7 years; stature 177.7 ± 5.6 cm; body mass 73.2 ± 8.6 kg) performed 1 lap of a 3.48 km mountain bike (MTB) course as fast as possible on 26″, 27.5″ and 29″ wheeled MTB. Time (s), mean power (W), cadence (revs · min−1) and velocity (km · h−1) were recorded for the whole lap and during ascent and descent sections. One-way repeated measure ANOVA was used to determine significant differences. Results revealed no significant main effects for any variables by wheel size during all trials, with the exception of cadence during the descent (F(2, 16) = 8.96; P = .002; P2 = .53). Post hoc comparisons revealed differences lay between the 26″ and 29″ wheels (P = .02). The findings indicate that wheel size does not significantly influence performance during cross-country when ridden by trained mountain bikers, and that wheel choice is likely due to personal choice or sponsorship commitments

Variability in Laboratory vs. Field Testing of Peak Power, Torque, and Time of Peak Power Production Among Elite Bicycle Motocross Cyclists

The aim of this study was to ascertain the variation in elite male bicycle motocross (BMX) cyclists' peak power, torque, and time of power production during laboratory and field-based testing. Eight elite male BMX riders volunteered for the study, and each rider completed 3 maximal sprints using both a Schoberer Rad Messtechnik (SRM) ergometer in the laboratory and a portable SRM power meter on an Olympic standard indoor BMX track. The results revealed a significantly higher peak power (p <= 0.001, 34 ± 9%) and reduced time of power production (p <= 0.001, 105 ± 24%) in the field tests when compared with laboratory-derived values. Torque was also reported to be lower in the laboratory tests but not to an accepted level of significance (p = 0.182, 6 ± 8%). These results suggest that field-based testing may be a more effective and accurate measure of a BMX rider's peak power, torque, and time of power production

Effect of cadence selection on peak power and time of power production in elite BMX riders; a laboratory based study.

The aims of this study were to analyse the optimal cadence for peak power production and time to peak power in bicycle motocross (BMX) riders. Six male elite BMX riders volunteered for the study. Each rider completed 3 maximal sprints at a cadence of 80, 100, 120 and 140revs·min-1 on a laboratory Schoberer Rad Messtechnik (SRM) cycle ergometer in isokinetic mode. The riders’ mean values for peak power and time of power production in all three tests were recorded. The BMX riders produced peak power (1105±139W) at 100revs·min-1 with lower peak power produced at 80revs:min-1 (1060±69W, (F(2,15)=3.162; p=.266; η2 =0.960), 120revs·min-1 (1077±141W, (F(2,15)=4.348; p=.203; η2 =0.970) and 140revs·min-1 (1046±175W, (F(2,15)=12.350; p=0.077; η2 =0.989). The shortest time to power production was attained at 120revs·min-1 in 2.5±1.07s. Whilst a cadence of 80revs:min-1 (3.5±0.8s, (F(2,15)=2.667; p=.284; η2 =0.800) 100revs:min-1 (3.00±1.13s, (F(2,15)=24.832; p=.039; η2 =0.974) and 140revs:min-1 (3.50±0.88s, (F(2,15)=44.167; p=.006; η2 =0.967)) all recorded a longer time to peak power production. The results indicate that the optimal cadence for producing peak power output and reducing the time to peak power output are attained at comparatively low cadences for sprint cycling events. These findings could potentially inform strength and conditioning training to maximise dynamic force production and enable coaches to select optimal gear ratios

GPS-Based Evaluation of Activity Profiles in Elite Downhill Mountain Biking and the Influence of Course Type

Abstract This study aimed to profile the activity patterns of elite downhill (DH) mountain bikers during off-road descending, and to determine the influence of course types on activity patterns. Six male elite DH mountain bikers (age 20 ± 2 yrs; stature 178.8 ± 3.1 cm; body mass 75.0 ± 3.0 kg) performed single runs on one man-made (MM) and one natural terrain (NT) DH courses under race conditions. A 5 Hz global positioning systems (GPS) unit, including a 100 Hz triaxial accelerometer, was positioned in a neoprene harness between the C7 and T2 vertebrae on each rider. GPS was used to determine the temporal characteristics of each run for velocity, run time, distance, effort, heart rate (HR), rider load (RLd) which reflects instantaneous rate of change in acceleration, and accumulated rider load (RLdAcc), which reflects change in acceleration over the event duration. Significant differences were found between NT and MM courses for mean velocity (p&lt;.001), peak velocity (p=.014), mean RLd (p=.001) and peak RLd (p=.002). Significant differences were also found both within and between courses for all velocity parameters, when analysed by intensity zone (p&lt;.05). No significant differences were found between courses for HR parameters by zone, though significant differences were revealed between HR zones within courses (p&lt;.05). This study indicates that course terrain has a significant impact on the activity profiles of DH and that GPS can provide a practical means of monitoring these differences in activity

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

Physical, cognitive, and mental health impacts of COVID-19 after hospitalisation (PHOSP-COVID): a UK multicentre, prospective cohort study

Background: The impact of COVID-19 on physical and mental health and employment after hospitalisation with acute disease is not well understood. The aim of this study was to determine the effects of COVID-19-related hospitalisation on health and employment, to identify factors associated with recovery, and to describe recovery phenotypes. // Methods: The Post-hospitalisation COVID-19 study (PHOSP-COVID) is a multicentre, long-term follow-up study of adults (aged ≥18 years) discharged from hospital in the UK with a clinical diagnosis of COVID-19, involving an assessment between 2 and 7 months after discharge, including detailed recording of symptoms, and physiological and biochemical testing. Multivariable logistic regression was done for the primary outcome of patient-perceived recovery, with age, sex, ethnicity, body-mass index, comorbidities, and severity of acute illness as covariates. A post-hoc cluster analysis of outcomes for breathlessness, fatigue, mental health, cognitive impairment, and physical performance was done using the clustering large applications k-medoids approach. The study is registered on the ISRCTN Registry (ISRCTN10980107). // Findings: We report findings for 1077 patients discharged from hospital between March 5 and Nov 30, 2020, who underwent assessment at a median of 5·9 months (IQR 4·9–6·5) after discharge. Participants had a mean age of 58 years (SD 13); 384 (36%) were female, 710 (69%) were of white ethnicity, 288 (27%) had received mechanical ventilation, and 540 (50%) had at least two comorbidities. At follow-up, only 239 (29%) of 830 participants felt fully recovered, 158 (20%) of 806 had a new disability (assessed by the Washington Group Short Set on Functioning), and 124 (19%) of 641 experienced a health-related change in occupation. Factors associated with not recovering were female sex, middle age (40–59 years), two or more comorbidities, and more severe acute illness. The magnitude of the persistent health burden was substantial but only weakly associated with the severity of acute illness. Four clusters were identified with different severities of mental and physical health impairment (n=767): very severe (131 patients, 17%), severe (159, 21%), moderate along with cognitive impairment (127, 17%), and mild (350, 46%). Of the outcomes used in the cluster analysis, all were closely related except for cognitive impairment. Three (3%) of 113 patients in the very severe cluster, nine (7%) of 129 in the severe cluster, 36 (36%) of 99 in the moderate cluster, and 114 (43%) of 267 in the mild cluster reported feeling fully recovered. Persistently elevated serum C-reactive protein was positively associated with cluster severity. // Interpretation: We identified factors related to not recovering after hospital admission with COVID-19 at 6 months after discharge (eg, female sex, middle age, two or more comorbidities, and more acute severe illness), and four different recovery phenotypes. The severity of physical and mental health impairments were closely related, whereas cognitive health impairments were independent. In clinical care, a proactive approach is needed across the acute severity spectrum, with interdisciplinary working, wide access to COVID-19 holistic clinical services, and the potential to stratify care