Page 1 of 28
Appl. Physiol. Nutr. Metab. Downloaded from www.nrcresearchpress.com by University of Otago on 09/05/14 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record.
Effect of cycle vs run SIT on VO2 1 2
Mode of exercise and sex are not important for oxygen consumption during and in recovery from sprint interval training
3 4 5 6 7 8 9 10
Logan K. Townsend1, Katie M. Couture2, Tom J. Hazell1 1
Department of Kinesiology and Physical Education, Faculty of Science Wilfrid Laurier University, Waterloo, Ontario, CANADA, N2L 3C5 2
Department of Kinesiology and Physical Education, Faculty of Arts and Science University of Lethbridge, Lethbridge, Alberta, CANADA, T1K 3M4
11
Co-Authors:
12 13
Logan K. Townsend [email protected]
14 15
Katie M. Couture [email protected]
16 17
Communicating Author:
18 19 20 21 22 23 24 25
Tom J. Hazell, PhD Department of Kinesiology and Physical Education Wilfrid Laurier University 75 University Ave W Waterloo, Ontario, CANADA, N2L 3C5 Email: [email protected] Tel: 519-884-1970 x4773 Fax: 519-474-4594
1
Page 2 of 28
Appl. Physiol. Nutr. Metab. Downloaded from www.nrcresearchpress.com by University of Otago on 09/05/14 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record.
Effect of cycle vs run SIT on VO2 26
Abstract
27
Most sprint interval training (SIT) research involves cycling as the mode of exercise and whether
28
running SIT elicits a similar excess post-exercise O2 consumption (EPOC) response to cycling
29
SIT is unknown. As running is a more whole-body natured exercise, the potential EPOC
30
response could be greater when using a running compared to cycling. The purpose of the current
31
study was to determine the acute effects of a running versus cycling SIT session on EPOC and
32
whether potential sex differences exist. Sixteen healthy recreationally active individuals (8
33
males and 8 females) had their gas exchange measured over ~2.5 h under three experimental
34
sessions: 1) a cycle SIT session; 2) a run SIT session; 3) and a control (CTRL; no exercise)
35
session. Diet was controlled. During exercise, both SIT modes increased VO2 (cycle – male:
36
1.967±0.343; female: 1.739±0.296 L⋅min-1; run – male: 2.169±0.369; female: 1.791±0.481
37
L⋅min-1) vs CTRL (male: 0.425±0.065 L⋅min-1; female: 0.357±0.067; P0.05). Our data demonstrate that
44
the mode of exercise during SIT (cycling or running) is not important to O2 consumption and that
45
males and females respond similarly.
46 47
KEYWORDS: EPOC; energy expenditure; sprint exercise; metabolism; post-exercise
2
Page 3 of 28
Appl. Physiol. Nutr. Metab. Downloaded from www.nrcresearchpress.com by University of Otago on 09/05/14 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record.
Effect of cycle vs run SIT on VO2 48
INTRODUCTION
49
Due to the prevalence of excess caloric intake and the adoption of increasingly sedentary
50
lifestyles, obesity has reached epidemic proportions (Hawley and Gibala 2009). While regular
51
physical activity is an obvious remedy, people often do not exercise due to a perceived lack of
52
time and lack of enjoyment (Godin et al. 1994, Leslie et al. 1999, Reichert et al. 2007, Sallis et
53
al. 1997, Stutts 2002, Trost et al. 2002). High-intensity interval training (HIT) has emerged as a
54
time-efficient training method to improve body composition (Boutcher 2011) and participants
55
recently demonstrated high confidence in their ability complete the intervals (1 min at 70 or
56
100% peak work rate followed by 1 min rest) as well as schedule HIT schedule it into their
57
weekly routine (Boyd et al. 2013). Further, other research has suggested that HIT (6 bouts of 3
58
min at 90% VO2max followed by 3 min rest) was more enjoyable than traditional moderate-
59
intensity continuous exercise of 50 min at 70% VO2max (Bartlett et al. 2011). A more potent
60
form of HIT is sprint interval training (SIT), which can be distinguished from more conventional
61
HIT by its increased intensity (i.e. super-maximal) and its shorter durations (10-30 sec) (Weston
62
et al. 2014). Specifically, SIT is a time efficient training method that involves repeated 30-
63
second “all-out” exercise efforts separated by 4 min of active recovery amounting to 2-3 min of
64
exercise in an 18-27 min exercise session. This SIT paradigm has proven to be a time effective
65
method to accrue metabolic and performance adaptations similar to those of traditional
66
continuous aerobic exercise training (Gibala et al. 2006, MacPherson et al. 2011), while also
67
improving body composition (Hazell et al. 2014, MacPherson et al. 2011). Some SIT research
68
has demonstrated no change in body mass (Burgomaster et al. 2008) or body composition
69
measured with skinfold fat measures (Astorino et al. 2011) and air displacement
3
Page 4 of 28
Appl. Physiol. Nutr. Metab. Downloaded from www.nrcresearchpress.com by University of Otago on 09/05/14 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record.
Effect of cycle vs run SIT on VO2 70
plethysmography (Hazell et al. 2010), though these were only over 2 weeks of SIT (6 exercise
71
sessions) and potential changes were not expected.
72
While the potential mechanisms for improved body composition with SIT are not well
73
understood, it would appear that some increase in post-exercise metabolism is likely a
74
contributing factor as the VO2 during an SIT session is much less than a continuous aerobic
75
exercise session (Hazell et al. 2012). Excess post-exercise oxygen consumption is the increased
76
oxygen utilized above rest post-exercise (Gaesser and Brooks 1984) and depends on both
77
exercise intensity and duration (Borsheim and Bahr 2003, Laforgia et al. 2006, Sedlock et al.
78
1989). A single SIT session has been demonstrated to increase EPOC (~14 L or 70 kcal) in the 2
79
h post-exercise (Chan and Burns 2013) and perhaps more importantly to increase total O2
80
consumed over 24 h vs continuous aerobic exercise (Hazell et al. 2012). However, there is also
81
research suggesting very little EPOC occurring in response to a single SIT session vs continuous
82
aerobic exercise (Williams et al. 2013). This limited research on SIT and EPOC has also been
83
limited to male participants and whether the responses are similar in females is unknown.
84
Furthermore, women performing SIT may have smaller decreases in fat mass following training
85
(MacPherson et al. 2011) suggesting there may be a gender specific response to SIT.
86
As running SIT has demonstrated fat loss (Hazell et al. 2014, MacPherson et al. 2011)
87
with potential contribution from an increase in EPOC, only cycling SIT has been measured post-
88
exercise (Hazell et al. 2012, Skelly et al. 2014) and whether running SIT elicits a similar EPOC
89
response to cycling SIT is unknown. Different physiological responses to cycling and running
90
have been previously demonstrated where fat oxidation is significantly higher while running than
91
cycling at the same relative intensity (Achten et al. 2003, Capostagno and Bosch 2010). In
92
addition, oxygen consumption is 7-10% higher for running as compared to cycling (Achten et al.
4
Page 5 of 28
Appl. Physiol. Nutr. Metab. Downloaded from www.nrcresearchpress.com by University of Otago on 09/05/14 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record.
Effect of cycle vs run SIT on VO2 93
2003, Hill et al. 2003) and time to achieve VO2max is more rapid when running (Hill et al. 2003).
94
As running is a more whole-body natured exercise, these data suggest the potential EPOC
95
response should be greater when using a running mode of SIT compared to a cycling mode.
96
Therefore, the purpose of the present study was to determine the acute effects of a single run vs
97
cycle SIT session on EPOC and whether there are potential sex differences. We hypothesized
98
that running will elicit a greater EPOC than cycling and males and females would respond
99
similarly.
100
101
METHODS
102
Protocol Overview
103
Sixteen healthy recreationally active individuals (8 males and 8 females) had their gas
104
exchange measured over ~2.5 h under three experimental sessions: 1) a cycling SIT session; 2) a
105
running SIT session; 3) and a control (CTRL; no exercise) session. All treatments were
106
separated by a minimum of 72 h. All participants were non-smokers, physically active but not
107
involved in an exercise training program at the time of data collection (or for at least 4 months
108
prior to data collection), and none were taking dietary supplements. Participants were instructed
109
to perform no physical activity or ingest any caffeine for 48 h prior to data collection.
110
Nutritional intake the morning of the first data collection section was recorded and provided back
111
to the participant’s before their next session so they could replicate that intake. No other
112
physical activity other than the prescribed exercise was performed. To avoid order effects, the
113
three treatments were administered via balanced randomized exposure to treatment order (Hazell
114
et al. 2012).
5
Page 6 of 28
Appl. Physiol. Nutr. Metab. Downloaded from www.nrcresearchpress.com by University of Otago on 09/05/14 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record.
Effect of cycle vs run SIT on VO2 115
Prior to the initiation of the study all participants provided their informed written consent,
116
passed the Physical Activity Readiness Questionnaire (PAR-Q) health survey (Thomas et al.
117
1992) and participated in a familiarization visit (5 days before 1st experimental session). During
118
the familiarization session, participants were fitted with a respiratory mask to become
119
accustomed to breathing with the mask on as well as practicing using the cycle ergometer and
120
specialized treadmill. The University of Lethbridge Human Subjects Research Committee
121
approved this study in accordance with the ethical standards of the 1964 Declaration of Helsinki.
122
Experimental Protocol
123
Participants arrived in the lab at 1100 h after having not eaten for 3 h. Upon arrival,
124
participants sat quietly in a chair for 20 minutes. Participants were fitted with a silicone
125
collection facemask (Vmask, Hans Rudolph, Inc., Shawnee, Kansas, USA). Gas exchange was
126
then gathered continuously for the next 158 minutes (15 min resting, 5 min warm-up, 18 min SIE
127
session, 5 min cool-down, 120 min post-exercise; Figure 1).
128
(VO2, VCO2) were made using an online breath-by-breath gas collection and analysis system
129
(Quark CPET, Cosmed, Rome, Italy). Prior to data collection the gas analyzers were calibrated
130
with gases of known concentrations and flow with a 3-L syringe. All measures were collected
131
while participants were seated in a chair in a temperature-controlled room (21 °C). Heart rate
132
(HR) was also collected continuously using a Cosmed HR belt. To calculate EPOC, VO2 from
133
the CTRL session was subtracted from the VO2 of either the running SIT or cycling SIT data.
134
Total session VO2 was calculated by using the average VO2 for the distinct phases of the session:
135
rest (15 min), warm-up (5 min), exercise session (18 min), and recovery (120 min). These values
136
were then multiplied by the associated time period to convert to litres of O2. Total kilocalories
137
(kcal) was calculated using the total VO2 from exercise and post-exercise and an assumed
All gas exchange measurements
6
Page 7 of 28
Appl. Physiol. Nutr. Metab. Downloaded from www.nrcresearchpress.com by University of Otago on 09/05/14 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record.
Effect of cycle vs run SIT on VO2 138
relationship of 5 kcal per L of VO2 as RER is not an accurate measure of fuel utilization after
139
sprint interval exercise (Binzen et al. 2001, Thornton and Potteiger 2002).
140
Exercise sessions
141
The cycle SIT session consisted of a 5 min warm-up (at 1 kg resistance, ~70 W) followed
142
by an 18 min SIT session and 5 min cool down (for a total session duration of 28 min). The
143
sprint bouts included four repeated 30-sec “all-out” efforts on a cycle ergometer (model 874-E,
144
Monark Exercise, Stockholm, Sweden) at 7.5% body mass. Each sprint bout was followed by 4
145
min active recovery (light cycling) with no added resistance. Instructions to begin pedaling as
146
fast as possible against the inertial resistance of the ergometer were given and the appropriate
147
load was applied instantaneously (within 3 s). Verbal encouragement was provided for the
148
remainder of the 30-s test. Peak power (highest output over first 5 s), average power (over the
149
entire effort), and minimum power (lowest output) were determined using an online data-
150
acquisition system (SMI power version 5.2.8, SMI optosensor, St. Cloud, Minnesota, USA).
151
The run SIT session was performed in an identical manner to the cycling, except
152
participants ran on a self-propelled treadmill (Curve, Woodway®, Waukesha, Wisconsin, USA)
153
allowing the participant to be the power source for the running belt, i.e. the treadmill would
154
move as fast as the participant could possibly run. The warm-up speed was ~3 mph while the
155
“all-out” efforts had each participant run as fast as possible. Each sprint bout was also followed
156
by 4 min of active recovery (walking slowly on treadmill). Instructions to begin running as fast
157
as possible were given upon test initiation.
158
remainder of the 30-s test. Peak speed (kph) was recorded as the fastest speed attained in the
159
first 5-10 s, and speed (kph) was recorded at every 5 s interval in order to calculate average
Verbal encouragement was provided for the
7
Page 8 of 28
Appl. Physiol. Nutr. Metab. Downloaded from www.nrcresearchpress.com by University of Otago on 09/05/14 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record.
Effect of cycle vs run SIT on VO2 160
speed (speed at each interval divided by 6) and minimum speed (lowest speed reached during the
161
test).
162
Nutritional Intake Dietary control was maintained by having all participants record their food intake for
163 164
breakfast on the first day of data collection. This dietary intake was provided to them (via email)
165
before any subsequent data collection with the instruction to reproduce this diet (2,814±1,463 kJ;
166
672±349 kcal; 97.1±68.8 g carbohydrate; 21.4±14.3 g fat; 34.5±21.9 g protein).
167
Statistical Analysis All data were analyzed using SPSS Statistics (Version 22). Two-way repeated measures
168 169
analysis of variance (ANOVA) with sex as a between subjects factor was used to determine
170
differences in VO2, RER, and HR among the three treatments (cycle SIT, run SIT, and CTRL) at
171
each time point (during, 1st h post-exercise, 2nd h post-exercise). All data are presented as
172
mean±SD and the level of statistical significance is set at P
Appl. Physiol. Nutr. Metab. Downloaded from www.nrcresearchpress.com by University of Otago on 09/05/14 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record.
Effect of cycle vs run SIT on VO2 1 2
Mode of exercise and sex are not important for oxygen consumption during and in recovery from sprint interval training
3 4 5 6 7 8 9 10
Logan K. Townsend1, Katie M. Couture2, Tom J. Hazell1 1
Department of Kinesiology and Physical Education, Faculty of Science Wilfrid Laurier University, Waterloo, Ontario, CANADA, N2L 3C5 2
Department of Kinesiology and Physical Education, Faculty of Arts and Science University of Lethbridge, Lethbridge, Alberta, CANADA, T1K 3M4
11
Co-Authors:
12 13
Logan K. Townsend [email protected]
14 15
Katie M. Couture [email protected]
16 17
Communicating Author:
18 19 20 21 22 23 24 25
Tom J. Hazell, PhD Department of Kinesiology and Physical Education Wilfrid Laurier University 75 University Ave W Waterloo, Ontario, CANADA, N2L 3C5 Email: [email protected] Tel: 519-884-1970 x4773 Fax: 519-474-4594
1
Page 2 of 28
Appl. Physiol. Nutr. Metab. Downloaded from www.nrcresearchpress.com by University of Otago on 09/05/14 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record.
Effect of cycle vs run SIT on VO2 26
Abstract
27
Most sprint interval training (SIT) research involves cycling as the mode of exercise and whether
28
running SIT elicits a similar excess post-exercise O2 consumption (EPOC) response to cycling
29
SIT is unknown. As running is a more whole-body natured exercise, the potential EPOC
30
response could be greater when using a running compared to cycling. The purpose of the current
31
study was to determine the acute effects of a running versus cycling SIT session on EPOC and
32
whether potential sex differences exist. Sixteen healthy recreationally active individuals (8
33
males and 8 females) had their gas exchange measured over ~2.5 h under three experimental
34
sessions: 1) a cycle SIT session; 2) a run SIT session; 3) and a control (CTRL; no exercise)
35
session. Diet was controlled. During exercise, both SIT modes increased VO2 (cycle – male:
36
1.967±0.343; female: 1.739±0.296 L⋅min-1; run – male: 2.169±0.369; female: 1.791±0.481
37
L⋅min-1) vs CTRL (male: 0.425±0.065 L⋅min-1; female: 0.357±0.067; P0.05). Our data demonstrate that
44
the mode of exercise during SIT (cycling or running) is not important to O2 consumption and that
45
males and females respond similarly.
46 47
KEYWORDS: EPOC; energy expenditure; sprint exercise; metabolism; post-exercise
2
Page 3 of 28
Appl. Physiol. Nutr. Metab. Downloaded from www.nrcresearchpress.com by University of Otago on 09/05/14 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record.
Effect of cycle vs run SIT on VO2 48
INTRODUCTION
49
Due to the prevalence of excess caloric intake and the adoption of increasingly sedentary
50
lifestyles, obesity has reached epidemic proportions (Hawley and Gibala 2009). While regular
51
physical activity is an obvious remedy, people often do not exercise due to a perceived lack of
52
time and lack of enjoyment (Godin et al. 1994, Leslie et al. 1999, Reichert et al. 2007, Sallis et
53
al. 1997, Stutts 2002, Trost et al. 2002). High-intensity interval training (HIT) has emerged as a
54
time-efficient training method to improve body composition (Boutcher 2011) and participants
55
recently demonstrated high confidence in their ability complete the intervals (1 min at 70 or
56
100% peak work rate followed by 1 min rest) as well as schedule HIT schedule it into their
57
weekly routine (Boyd et al. 2013). Further, other research has suggested that HIT (6 bouts of 3
58
min at 90% VO2max followed by 3 min rest) was more enjoyable than traditional moderate-
59
intensity continuous exercise of 50 min at 70% VO2max (Bartlett et al. 2011). A more potent
60
form of HIT is sprint interval training (SIT), which can be distinguished from more conventional
61
HIT by its increased intensity (i.e. super-maximal) and its shorter durations (10-30 sec) (Weston
62
et al. 2014). Specifically, SIT is a time efficient training method that involves repeated 30-
63
second “all-out” exercise efforts separated by 4 min of active recovery amounting to 2-3 min of
64
exercise in an 18-27 min exercise session. This SIT paradigm has proven to be a time effective
65
method to accrue metabolic and performance adaptations similar to those of traditional
66
continuous aerobic exercise training (Gibala et al. 2006, MacPherson et al. 2011), while also
67
improving body composition (Hazell et al. 2014, MacPherson et al. 2011). Some SIT research
68
has demonstrated no change in body mass (Burgomaster et al. 2008) or body composition
69
measured with skinfold fat measures (Astorino et al. 2011) and air displacement
3
Page 4 of 28
Appl. Physiol. Nutr. Metab. Downloaded from www.nrcresearchpress.com by University of Otago on 09/05/14 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record.
Effect of cycle vs run SIT on VO2 70
plethysmography (Hazell et al. 2010), though these were only over 2 weeks of SIT (6 exercise
71
sessions) and potential changes were not expected.
72
While the potential mechanisms for improved body composition with SIT are not well
73
understood, it would appear that some increase in post-exercise metabolism is likely a
74
contributing factor as the VO2 during an SIT session is much less than a continuous aerobic
75
exercise session (Hazell et al. 2012). Excess post-exercise oxygen consumption is the increased
76
oxygen utilized above rest post-exercise (Gaesser and Brooks 1984) and depends on both
77
exercise intensity and duration (Borsheim and Bahr 2003, Laforgia et al. 2006, Sedlock et al.
78
1989). A single SIT session has been demonstrated to increase EPOC (~14 L or 70 kcal) in the 2
79
h post-exercise (Chan and Burns 2013) and perhaps more importantly to increase total O2
80
consumed over 24 h vs continuous aerobic exercise (Hazell et al. 2012). However, there is also
81
research suggesting very little EPOC occurring in response to a single SIT session vs continuous
82
aerobic exercise (Williams et al. 2013). This limited research on SIT and EPOC has also been
83
limited to male participants and whether the responses are similar in females is unknown.
84
Furthermore, women performing SIT may have smaller decreases in fat mass following training
85
(MacPherson et al. 2011) suggesting there may be a gender specific response to SIT.
86
As running SIT has demonstrated fat loss (Hazell et al. 2014, MacPherson et al. 2011)
87
with potential contribution from an increase in EPOC, only cycling SIT has been measured post-
88
exercise (Hazell et al. 2012, Skelly et al. 2014) and whether running SIT elicits a similar EPOC
89
response to cycling SIT is unknown. Different physiological responses to cycling and running
90
have been previously demonstrated where fat oxidation is significantly higher while running than
91
cycling at the same relative intensity (Achten et al. 2003, Capostagno and Bosch 2010). In
92
addition, oxygen consumption is 7-10% higher for running as compared to cycling (Achten et al.
4
Page 5 of 28
Appl. Physiol. Nutr. Metab. Downloaded from www.nrcresearchpress.com by University of Otago on 09/05/14 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record.
Effect of cycle vs run SIT on VO2 93
2003, Hill et al. 2003) and time to achieve VO2max is more rapid when running (Hill et al. 2003).
94
As running is a more whole-body natured exercise, these data suggest the potential EPOC
95
response should be greater when using a running mode of SIT compared to a cycling mode.
96
Therefore, the purpose of the present study was to determine the acute effects of a single run vs
97
cycle SIT session on EPOC and whether there are potential sex differences. We hypothesized
98
that running will elicit a greater EPOC than cycling and males and females would respond
99
similarly.
100
101
METHODS
102
Protocol Overview
103
Sixteen healthy recreationally active individuals (8 males and 8 females) had their gas
104
exchange measured over ~2.5 h under three experimental sessions: 1) a cycling SIT session; 2) a
105
running SIT session; 3) and a control (CTRL; no exercise) session. All treatments were
106
separated by a minimum of 72 h. All participants were non-smokers, physically active but not
107
involved in an exercise training program at the time of data collection (or for at least 4 months
108
prior to data collection), and none were taking dietary supplements. Participants were instructed
109
to perform no physical activity or ingest any caffeine for 48 h prior to data collection.
110
Nutritional intake the morning of the first data collection section was recorded and provided back
111
to the participant’s before their next session so they could replicate that intake. No other
112
physical activity other than the prescribed exercise was performed. To avoid order effects, the
113
three treatments were administered via balanced randomized exposure to treatment order (Hazell
114
et al. 2012).
5
Page 6 of 28
Appl. Physiol. Nutr. Metab. Downloaded from www.nrcresearchpress.com by University of Otago on 09/05/14 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record.
Effect of cycle vs run SIT on VO2 115
Prior to the initiation of the study all participants provided their informed written consent,
116
passed the Physical Activity Readiness Questionnaire (PAR-Q) health survey (Thomas et al.
117
1992) and participated in a familiarization visit (5 days before 1st experimental session). During
118
the familiarization session, participants were fitted with a respiratory mask to become
119
accustomed to breathing with the mask on as well as practicing using the cycle ergometer and
120
specialized treadmill. The University of Lethbridge Human Subjects Research Committee
121
approved this study in accordance with the ethical standards of the 1964 Declaration of Helsinki.
122
Experimental Protocol
123
Participants arrived in the lab at 1100 h after having not eaten for 3 h. Upon arrival,
124
participants sat quietly in a chair for 20 minutes. Participants were fitted with a silicone
125
collection facemask (Vmask, Hans Rudolph, Inc., Shawnee, Kansas, USA). Gas exchange was
126
then gathered continuously for the next 158 minutes (15 min resting, 5 min warm-up, 18 min SIE
127
session, 5 min cool-down, 120 min post-exercise; Figure 1).
128
(VO2, VCO2) were made using an online breath-by-breath gas collection and analysis system
129
(Quark CPET, Cosmed, Rome, Italy). Prior to data collection the gas analyzers were calibrated
130
with gases of known concentrations and flow with a 3-L syringe. All measures were collected
131
while participants were seated in a chair in a temperature-controlled room (21 °C). Heart rate
132
(HR) was also collected continuously using a Cosmed HR belt. To calculate EPOC, VO2 from
133
the CTRL session was subtracted from the VO2 of either the running SIT or cycling SIT data.
134
Total session VO2 was calculated by using the average VO2 for the distinct phases of the session:
135
rest (15 min), warm-up (5 min), exercise session (18 min), and recovery (120 min). These values
136
were then multiplied by the associated time period to convert to litres of O2. Total kilocalories
137
(kcal) was calculated using the total VO2 from exercise and post-exercise and an assumed
All gas exchange measurements
6
Page 7 of 28
Appl. Physiol. Nutr. Metab. Downloaded from www.nrcresearchpress.com by University of Otago on 09/05/14 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record.
Effect of cycle vs run SIT on VO2 138
relationship of 5 kcal per L of VO2 as RER is not an accurate measure of fuel utilization after
139
sprint interval exercise (Binzen et al. 2001, Thornton and Potteiger 2002).
140
Exercise sessions
141
The cycle SIT session consisted of a 5 min warm-up (at 1 kg resistance, ~70 W) followed
142
by an 18 min SIT session and 5 min cool down (for a total session duration of 28 min). The
143
sprint bouts included four repeated 30-sec “all-out” efforts on a cycle ergometer (model 874-E,
144
Monark Exercise, Stockholm, Sweden) at 7.5% body mass. Each sprint bout was followed by 4
145
min active recovery (light cycling) with no added resistance. Instructions to begin pedaling as
146
fast as possible against the inertial resistance of the ergometer were given and the appropriate
147
load was applied instantaneously (within 3 s). Verbal encouragement was provided for the
148
remainder of the 30-s test. Peak power (highest output over first 5 s), average power (over the
149
entire effort), and minimum power (lowest output) were determined using an online data-
150
acquisition system (SMI power version 5.2.8, SMI optosensor, St. Cloud, Minnesota, USA).
151
The run SIT session was performed in an identical manner to the cycling, except
152
participants ran on a self-propelled treadmill (Curve, Woodway®, Waukesha, Wisconsin, USA)
153
allowing the participant to be the power source for the running belt, i.e. the treadmill would
154
move as fast as the participant could possibly run. The warm-up speed was ~3 mph while the
155
“all-out” efforts had each participant run as fast as possible. Each sprint bout was also followed
156
by 4 min of active recovery (walking slowly on treadmill). Instructions to begin running as fast
157
as possible were given upon test initiation.
158
remainder of the 30-s test. Peak speed (kph) was recorded as the fastest speed attained in the
159
first 5-10 s, and speed (kph) was recorded at every 5 s interval in order to calculate average
Verbal encouragement was provided for the
7
Page 8 of 28
Appl. Physiol. Nutr. Metab. Downloaded from www.nrcresearchpress.com by University of Otago on 09/05/14 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record.
Effect of cycle vs run SIT on VO2 160
speed (speed at each interval divided by 6) and minimum speed (lowest speed reached during the
161
test).
162
Nutritional Intake Dietary control was maintained by having all participants record their food intake for
163 164
breakfast on the first day of data collection. This dietary intake was provided to them (via email)
165
before any subsequent data collection with the instruction to reproduce this diet (2,814±1,463 kJ;
166
672±349 kcal; 97.1±68.8 g carbohydrate; 21.4±14.3 g fat; 34.5±21.9 g protein).
167
Statistical Analysis All data were analyzed using SPSS Statistics (Version 22). Two-way repeated measures
168 169
analysis of variance (ANOVA) with sex as a between subjects factor was used to determine
170
differences in VO2, RER, and HR among the three treatments (cycle SIT, run SIT, and CTRL) at
171
each time point (during, 1st h post-exercise, 2nd h post-exercise). All data are presented as
172
mean±SD and the level of statistical significance is set at P
