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 points During cross-country skiing and indoor cycling VO2max and energy expenditure were higher than during alpine skiing Approximately 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 Key words: Borg, blood lactate, cross-country skiing, cycling, energy expenditure, fitness level, oxygen uptake, gender Introduction During the winter season the frequency of participating in physical activity and the total daily energy expenditure has been shown to be reduced when compared with the summer months (Dannenberg et al., 1989, Merchant et al., 2007). Furthermore, blood pressure, cholesterol and body mass index tend to increase in all age groups and both sexes during winter months, leading to an increasing risk of chronic coronary disease and cardiac events (Ulmer et al., 2004). Physical inactivity is one of the main modifiable risk factors of cardiovascular diseases and has been reported to be as deleterious as tobacco smoking (Mendis et al., 2011). Therefore, there is a need to identify modes of exercise and sports that are attractive to the wider population with the potential to maintain if not even increase physical fitness during winter. Indoor cycling (IC) might be regarded as the gold standard for physical training with no seasonal limitations and its feasibility for different target groups, i.e. those without access to mountains and snow or injuries and chronic disease that preclude them from participation in winter sports. Alpine and Nordic sports have a long standing tradition in alpine and Scandinavian countries. More than one third of all Austrians (~7.6 Million in the year 1986) think that alpine skiing (AS) is the best way to experience nature and freedom in the winter months (Bachleitner, 1998). AS has become the most popular winter sport world-wide, with more than eight million skiers visiting Austria each year (Burtscher et al., 2000). Alpine skiing is a leisure sport where gravity is the driving force and the work needed to raise the potential energy for the next downhill is provided by the chairlift not the skier as i.e. during alpine touring skiing or cross-country skiing (XCS). It is open to debate whether AS might provide sufficient cardiovascular and metabolic stimuli to achieve fitness gains. In the past few years, recent investigations have shown that AS is a suitable and safe recreational sport for an elderly and sedentary population (Kahn et al., 1993; Krautgasser et al., 2011; Muller et al., 2011; Potzelsberger et al., 2015; Scheiber et al., 2009; 2012). However, Karlsson et al. (1978) listed some limitations for recreational skiers not being able to reach high intensities during skiing due to poor technique and strength when compared with professional skiers. While there are several studies that discuss the physiological response during XCS in general (e.g. Mygind et al., 1991, Mognoni et al., 2001, Welde et al., 2003, Larsson and Henriksson-Larsen, 2008), research about the effects of fitness level on physiological response during XCS or IC is missing. Cross-country skiing can be regarded as the gold standard winter time aerobic exercise mode, with a high percentage of muscles in the whole body being activated (Rusko, 2008, Bjorklund et al., 2015, Stoggl et al., 2013, Bjorklund et al., 2010), and the highest VO2max values among all sports being measured in world class XCS athletes (Holmberg et al., 2007, Rusko, 2008, Saltin and Astrand, 1967). It is not known if AS can be used as an alternative to XCS and/or IC to fill the winter gap of physical activity and provide an alternative to indoor training. There are many studies that have analyzed the physiological responses of AS, XCS and IC separately (e.g., Bergh, 1982; Hoffman, 1992; Holmberg, 2005; Impellizzeri and Marcora, 2007; Mujika and Padilla, 2001; Kahn et al., 1993; Krautgasser et al., 2011; Muller et al., 2011; Potzelsberger et al., 2015; Scheiber et al., 2009; Vogt et al., 2005). However to the best of our knowledge, no direct comparisons within the same subjects were done while performing AS, XCS as well as IC. In addition, most of the previous studies included well-trained if not elite athletes, which is not representative of the common population. Furthermore, data about energy expenditure (EE) and MET values during AS are solely provided during the downhill phase (Ainsworth et al., 2011, Vogt et al., 2005) representing not a measure with sufficient external validity based on recovery periods while standing in line, taking a lift and short breaks during skiing of up to 67% of total skiing time (Muller et al., 2011). And lastly, sex, fitness and age aspects were largely neglected; and interactions of the above mentioned factors with exercise intensity and exercise mode (here IC vs. XCS vs. AS) are missing. Recently we have provided a first outline about the cardiorespiratory and metabolic response with AS, XCS and IC (Stoggl et al., 2015), however the detailed effects of exercise intensity, sex, age, fitness level and its interactions are open to be discussed. Therefore, in the current study we set out to 1) compare the metabolic and cardiorespiratory responses as well as rates of perceived exertion during AS to XCS and IC, 2) analyze the effects of gender, age and fitness level and its interaction with exercise intensity and exercise mode in this comparison, and 3) translate the duration of an AS session into isocaloric training sessions of XCS and IC.