Comparison of the Turn Switch Time Points Measured by Portable Force Platforms and Pressure Insoles.

Several methods to determine turn switch points during alpine skiing using the vertical GRF exist in the literature. Although comparative studies between pressure insoles (PI) and force platforms (FP) have been conducted, there are no reports comparing the detected time points. Yet, these sensors and methods have been used interchangeably. This study aims to compare the turn switch time points with both sensors and various methods. Twenty skiers performed turns with FP and PI for two different ski styles (high and low dynamic turns). Three different assessment methodologies were compared: minima, functional minima, and crossings. Bland Altman and repeated measures ANOVA were used to assess statistical differences. Main effects of sensor and method were observed (p < 0.001). Although there was a low effect size ( η p 2 = 0.013) between FP and PI, the 95% CI yielded values representing >30% of the turn duration. A large effect size (η2 = 0.153) was found between the crossing method and the minima and functional minima methods. This indicates that those methods assess different events during the turn switch phase. In conclusion, the sensors and assessment methodologies compared in this study are not interchangeable with the possible exception of the minima and functional minima assessed with FP.

Grade and speed have greater influence on HR and RPE than ability, sex, and age in alpine skiing.

The purpose of this study was to investigate the influence of ski slope grade, skiing speed, skiing ability, sex, and age on HR, RPE, and energy expenditure responses during recreational alpine skiing. Thirty-eight participants were divided by age, sex, and skiing ability. Instructor- and self-paced skiing conditions were conducted on 10° and 19.8° slopes. Skiing HR was recorded, RPE collected at the end of each run, and energy expenditure calculated. The pertinent results of this study demonstrate that the interactions of grade × speed, speed × age, and grade × age and the main effects of speed and grade significantly influenced %HRmax, mean HR, RPE, and energy expenditure during skiing. When %HRmax is taken into account, the older skiers skied at a greater relative intensity than the young skiers. The sex, age, and skiing ability main effects did not have a significant influence on mean HR, RPE, and energy expenditure. These data demonstrates that increased speed and grade results in increased physiological stress. Using mean, HR data may not be the best option for assessing physiological stress during exercise in the older athlete as it does not account for the influence of the ageing process.

A Comparison between Alpine Skiing, Cross-Country Skiing and Indoor Cycling on Cardiorespiratory and Metabolic Response.

Since physical inactivity especially prevails during winter months, we set out to identify outdoor alternatives to indoor cycling (IC) by comparing the metabolic and cardiorespiratory responses during alpine skiing (AS), cross-country skiing (XCS) and IC and analyse the effects of sex, age and fitness level in this comparison. Twenty one healthy subjects performed alpine skiing (AS), cross-country skiing (XCS), and IC. Oxygen uptake (VO2), total energy expenditure (EE), heart rate (HR), lactate, blood glucose and rate of perceived exertion (RPE) were determined during three 4-min stages of low, moderate and high intensity. During XCS and IC VO2max and EE were higher than during AS. At least 2½ hours of AS are necessary to reach the same EE as during one hour of XCS or IC. HR, VO2, lactate, and RPEarms were highest during XCS, whereas RPEwhole-body was similar and RPElegs lower than during AS and IC, respectively. Weight adjusted VO2 and EE were higher in men than in women while fitness level had no effect. Male, fit and young participants were able to increase their EE and VO2 values more pronounced. Both AS and XCS can be individually tailored to serve as alternatives to IC and may thus help to overcome the winter activity deficit. XCS was found to be the most effective activity for generating a high EE and VO2 while AS was the most demanding activity for the legs. Key pointsDuring cross-country skiing and indoor cycling VO2max and energy expenditure were higher than during alpine skiingApproximately 2½ hours of alpine skiing are necessary to reach the same energy expenditure of one hour of cross-country skiing or indoor cycling.Alpine skiing and cross-country skiing can be individually tailored to serve as sports alternatives in winter to activity deficit.By applying different skiing modes as parallel ski steering, carving long radii and short turn skiing, metabolic and cardiorespiratory response can be increased during alpine skiing.Male, fit and young participants were able to increase their energy expenditure and VO2 more pronounced with an increase in intensity compared with their counterparts.

Instructor-paced vs. self-paced skiing modes in older recreational alpine skiers.

Parallel ski steering (PSS), carving in long radii (CLR), and individual technique (IT) skiing modes are mainly used throughout instructor-guided skiing of older recreational skiers. The aims of this study were (a) to determine differences in the physiologic response of older skiers to PSS, CLR, and IT skiing modes, (b) to quantify correlations between rate of perceived exertion (RPE) and the physiologic response, and (c) to analyze the relationship between aerobic capacity, skiing skills, and the blood lactate (LA) response during instructor-guided skiing. Twenty recreational skiers (61.1 ± 5.6 years) performed instructor-paced (PSS and CLR) and self-paced (IT) skiing modes. Heart rate (HR), LA, mean arterial blood pressure (MAP), and RPE were determined during skiing. Skiers skiing skills were judged by expert ski instructors. The aerobic capacity was tested by a physical work capacity test (PWC130) test. Heart rate was lower for PSS (106 ± 15 b · min(-1)), compared to CLR (118 ± 16 b · min(-1)) and IT (120 ± 15 b · min(-1)) skiing modes, both p < 0.001. Lactate levels were 1.45 ± 0.50 mmol · L(-1) for PSS, 1.67 ± 0.61 mmol · L(-1) for CLR, and 2.00 ± 0.74 mmol · L(-1) for IT skiing modes, all p < 0.004. Individual reductions in LA concentrations from 3.9 to 2.6 mmol · L were found, for IT and PSS skiing modes, respectively. No significant correlations were determined between any physiologic variable and RPE. Weak correlations were found between LA and PWC130 results (R2 < 0.114) and between LA and skiing skills (R2 < 0.132). In conclusion, significant reductions in the physiologic response were determined for PSS and CLR, compared with IT skiing modes. Instructor-paced skiing modes may minimize the risk of premature fatigue of skiers with high physiological responses. Those skiers may not perceive their disproportionate higher stress compared with skiers on the low end.

Physiological responses of elderly recreational alpine skiers of different fitness and skiing abilities.

We measured physiological responses of elderly recreational skiers of different fitness and skiing abilities. Six subjects (mean age: 61.2 ± 4.6 yrs; Wt: 76.8 ± 15.6 kg; Ht: 1.69 ± 0.10 m; BMI: 26.9 ± 5.0) were tested in a laboratory and during 30 and 75 min of recreational downhill skiing. Oxygen uptake (VO2), heart rate (HR), blood lactate (LA) concentration, and diastolic (DBP) and systolic (SBP) blood pressure were used to estimate energy demands while skiing. During maximal testing in a laboratory, subjects achieved a mean maximal VO2max of 28.2 ± 7.5 ml.kg(-1).min(-1) and a mean HRpeak of 165 ± 4 bpm (98 ± 1% of HRmax). Mean maximal workload measured on a cycle ergometer was 2.2 ± 0.7 W.kg(-1) with a mean LApeak of 7.4 ± 1 mmol.l(-1). During field testing, mean VO2 during skiing was 12 ± 2 ml.kg(-1).min(-1) (45 ± 16% of VO2max). Skiing VO2peak was 19 ± 5 ml. kg(-1).min(-1) (72 ± 23% of VO2max) was lower than VO2max in the lab (p = 0.04). Mean HR during skiing was 126 ± 2 bpm (77 ± 1% of HRmax from lab tests). Skiing HRpeak was 162 ± 2 bpm. This was not different from HRmax in the lab (p = 0.68). Mean LA after 30 and 75 min of skiing was not different (2.2 ± 0.8 mmol.l(-1) and 2.0 ± 0.8, respectively, p = 0.71). Both LA samples during skiing were lower than lab tests (p < 0.0001). There was no difference for DBP between field and laboratory tests; however, SBP increased after 30 min of skiing to 171 ± 20 (p < 0.009) and 165 ± 17 (p < 0.003) after 75 min. These remained below the mean peak SBP determined in lab tests (218+31). Mean oxygen demand during 30 and 75 min of recreational skiing is only 45% of VO2max while mean HR is 77% of HRmax. This departure from linearity not often seen in typical aerobic activities suggests that alpine skiing requires a combination of aerobic and anaerobic activity. Blood LA remained low during skiing suggesting that elderly skiers may govern their intensity via signals closer to VO2 and LA compared to HR or BP. Key pointsRecreational Alpine skiing for elderly population does not pose health risksBlood pressure and heart rate during recreational Alpine skiing is retain within normal limitsBlood lactate levels remain relatively low and do not contribute to fatigueOxygen uptake and blood lactate are better markers of intensity in elderly Alpine skier compared to heart rate and blood pressure.

A comparison of ground reaction forces determined by portable force-plate and pressure-insole systems in alpine skiing.

For the determination of ground reaction forces in alpine skiing, pressure insole (PI) systems and portable force plate (FP) systems are well known and widely used in previous studies. The purposes of this study were 1) to provide reference data for the vertical component of the ground reaction forces (vGRF) during alpine skiing measured by the PI and FP systems, and 2) to analyze whether the differences in the vGRF measured by the PI and the FP depend on a skier's level, skiing mode and pitch. Ten expert and ten intermediate level skiers performed 10 double turns with the skiing technique "Carving in Short Radii" as High Dynamic Skiing mode and "Parallel Ski Steering in Long Radii" as Low Dynamic Skiing mode on both the steep (23 °) and the flat (15 °) slope twice. All subjects skied with both the PI and the FP system simultaneously. During the outside phase, the mean vGRF and the maximum vGRF determined by the FP are greater than the PI (p < 0.01). Additionally during the inside phase, the mean vGRF determined by the FP were greater than the PI (p < 0.01). During the edge changing phases, the mean vGRF determined by the FP were greater than the PI (p < 0.01). However, the minimum vGRF during the edge changing phases determined by the FP were smaller than the PI (p < 0.01) in the High-Steep skiing modes of Experts and Intermediates (p < 0.001). We have found that generally, the PI system underestimates the total vGRF compared to the FP system. However, this difference depends not only the phase in the turn (inside, outside, edge changing), but also is affected by the skier's level, the skiing mode performed and pitch. Key pointsTypically, during the steering phases of the ski turns the total vGRFs measured by the pressure-insole system were lower compared to the portable force-plate system.However, in some skiing modes during the edge changing phase, the pressure-insole system overestimates the total vGRF compared to the portable force-plate system.Differences between the forces determined by the both systems depend on the phase in the turn (inside, outside, edge changing) and are affected additionally by the skier's level, the performed skiing mode and pitch.

Physiologic responses of older recreational alpine skiers to different skiing modes.

We measured physiological variables in nine older recreational skiers (62.6 +/- 5.1 years) who completed a maximal cycle ergometry test and four different skiing modes via ski instructor-guided skiing at moderate altitude. During testing, we measured heart rate (HR), oxygen uptake (VO(2)), blood lactate concentration (LA), blood pressure (BP) and ratings of perceived exertion (RPE). The mean values in the laboratory were: HR(max) 167 +/- 7.9 bpm, VO(2peak) of 35.7 +/- 5.1 ml kg(-1) min(-1), LA(max) 8.9 +/- 2.4 mmol l(-1) and BP of 228/91 mmHg. The average values of field compared to laboratory test ranged from 48 to 94% of HR(max), VO(2) of 22-66% of VO(2peak), LA of 0.7-6.0 mmol l(-1), RPE during on-snow was 6-17, while BP remained at submaximal level during field tests. Weak correlation was found between laboratory and field tests. Our results suggest that aerobic metabolism predominates on flat and low intensity steep slopes and transitions to anaerobic metabolism on steeper high intensity runs.