obesity is one of the greatest public health challenges of the 21st century . between 1980 and 2008 ,
behavioral risk factors including physical inactivity and unhealthy diet are estimated to be responsible for about 80% of coronary heart disease and cerebrovascular disease .
obesity drastically increases the individual risk of developing chronic metabolic diseases , such as cardiovascular disease , cancer , and diabetes mellitus .
in particular , type 2 diabetes mellitus ( t2 dm ) is a worldwide pathological condition associated with obesity and sedentary lifestyle . interestingly ,
adipose tissue excess and physical inactivity have led to the development of a pathological condition defined as  sarcopenic obesity .  hence , sarcopenic obesity prevalence ranges from 2.75% to over 20% , depending on the criteria used for the diagnosis and methods of body composition assessment .
sarcopenia has been described as age - related loss of muscle mass that results in decreased strength , aerobic power , and functional capacity [ 4 , 5 ] .
thus , sarcopenic obesity condition is commonly observed in older people   but , more recently , it can also be observed in younger adults , likely linked to physical inactivity and sedentary behavior [ 6 , 7 ] .
moreover , recent data have demonstrated that obese t2 dm patients have an impaired muscle strength which could increase adverse events in these subjects . physical activity ( pa ) , along with correct nutritional intervention , is considered crucial for the prevention and management of both sarcopenic obesity and diabetes .
indeed , it is well known that regular pa is an essential component in primary and secondary prevention for most of the ncds since it provides several health benefits [ 9 , 10 ] .
pa treatment goals in obese patients with sarcopenia or diabetes include achievement of optimal body composition , aerobic and functional capacity .
it is well known that exercise is more efficient when is structured and performed after a precise prescription and with serious coaching and follow - up .
however , few issues need to be further evaluated and characterized when pa is prescribed to obese individuals .
for instance , the role of exercise intensity in physical training adherence might play a fundamental role [ 11 , 12 ] . individualizing the exercise intensity after an exercise test in order to perform moderate intensity it has been reported to provide positive results .
indeed , exercise intensity should be set to reach positive physiological effects , a decreased risk of injury , and increased adherence .
pa can elicit different responses in obese individuals when prescribed in absolute terms , such as gait speed and power , since no individual adjustment is usually made for each subject 's exercise capacity .
moreover , the use of relative terms such as % vo2max and % hrmax has been substantially criticized [ 9 , 14 , 15 ] since it seems that the relative parameters alone , without considering the individual ventilatory threshold ( ivt ) , are not sufficient and adequate to individualize exercise intensity . in particular
, ivt is the point after which ventilation begins to increase disproportionately relative to oxygen uptake so that it was called 
it is considered a useful submaximal breakpoint for optimal moderate exercise intensity prescription in t2 dm patients and obese subjects [ 17 , 18 ] .
the work load corresponding to these physiological events is sometimes termed  ventilatory threshold 1  or  aerobic threshold  ; we will use the term  individual ventilatory threshold  ( ivt ) for the rest of the text .
for t2 dm patients , predicting the ivt using only relative terms could not lead the specialist physical activity teacher to select the exercise intensity for optimal moderate intensity training .
seeing that the exercise intensity to perform moderate intensity training could be modified by a different pathological condition in obese subjects , it is very important to individualize the intensity of exercise after an individualized exercise test .
this approach may permit individualizing the target intensity training according to the different subjects ' pathological conditions .
moreover , dishman and buckworth   showed that activity - promotion efforts were more effective when the intensity of pa was low rather than high .
previous studies [ 21 , 22 ] showed that subjects would be more inclined to choose an exercise intensity around their ivt .
no data are available to date regarding exercise capacity in adult affected by sarcopenic obesity . as result
, we might hypothesize that differences could exist in responses during exercise among different obesity conditions at the same relative exercise intensity .
therefore , aim of our study was to evaluate whether differences could exist on physiological parameters at ivt and at maximal effort in obese with sarcopenia or diabetes mellitus subjects .
sixteen female obese subjects ( mean  sd : age : 58.8  7.8  yrs ) , sixteen female obese subjects with type 2 diabetes ( age : 60.0  10.0  yrs ) , and sixteen female sarcopenic obese individuals ( age : 60.9  13.0  yrs ) were selected in the department of experimental medicine , section of medical pathophysiology , food science and endocrinology , the policlinico umberto i , sapienza university of rome between january 2013 and june 2013 .
patients were divided into the groups based on the diagnosis of type 2 diabetes mellitus or sarcopenia ( as described in the following paragraph ) .
participants provided written informed consent and protocol was approved by the local ethical committee of policlinico umberto i , sapienza university of rome .
all subjects were sedentary and they had not been previously engaged in regular physical exercise .
subjects underwent clinical examination to rule out any contraindications to pa ( such as neuropathy , autonomic dysfunction , cardiovascular diseases , and blood pressure 140/90  mmhg ) .
body weight ( bw ) measurements were taken on a calibrated digital scale ( inbody 720 , biospace inc . ,
body mass index ( bmi ) was calculated as bw divided by squared height ( kg / m ) .
diagnosis of type 2 diabetes mellitus ( t2 dm ) was established according to the world health organization criteria   and t2 dm patients were on oral pharmacological treatments .
obesity was diagnosed as fat mass equal to or above 35% in women and 25% in men .
sarcopenia was diagnosed according to the definition by the european working group on sarcopenia in older people ( ewgsop ) , considering the reduction of muscle mass , the impairment of muscle strength , and physical performance .
ffm was considered low if a patient 's fat - free mass ( ffm ) was < 90% of their ideal ffm ( iffm ) .
ideal ffm was calculated in kg as the sum of 75% of ideal body weight and 25% of overweight , as expressed by a bmi > 24.9  kg / m [ 5 , 10 ] . body composition was evaluated by dexa ( hologic , bedford , united states ) and by body impedance assessment ( bia 101 impedance analyzer , akern , florence , italy ) .
dietary counselling and psychological counselling were performed by a dietitian and a psychologist , respectively .
a low - calorie diet was set at approximately 400kcal less than total daily energy expenditure in all patients .
total daily energy expenditure was set according to the following equation : resting metabolic rate + pa level .
resting metabolic rate was estimated by the harris benedict equation   while pa level was estimated by the international physical activity questionnaire ( ipaq ) .
pulmonary function tests and a resting electrocardiogram ( ecg ) recording were performed as initial screening in all patients .
prior to the test session , participants took part in a familiarization session to become accustomed to tests .
vo2peak was assessed in all participants by means of a continuous , maximal graded exercise test on a treadmill according to individual abilities . in particular , subjects performed an incremental protocol   on a treadmill ( pro treadmill , woodway , waukesha , wi , usa ) . during exercise testing
, subjects were asked to report the degree of exertion every two minutes , based on the rpe scale .
treadmill protocol started at 3  km / h and then speed increased by 1  km / h every two minutes until 5  km / h was reached .
then , slope was increased by 3% every two minutes until subjects reached a value of 10 on rpe scale .
heart rate ( beatsmin ) was continuously recorded before and throughout the trial using a hr monitor ( rs 400 , polar electro , kempele , finland ) . vo2 and pulmonary ventilation ( ve ) were measured by a semiportable gas analysis system ( fitmate pro , cosmed , rome , italy ) .
prior to each test , the fitmate pro underwent an automatic gas calibration cycle and the turbine flow meter was periodically calibrated using a 3 l syringe according to the manufacturer 's recommendations . during the test ,
the individual ventilatory threshold ( ivt ) was determined offline for each subject by plotting the ventilatory equivalent ( ve / vo2 ) as a function of vo2 to identify the point during exercise where this curve reached its lowest value [ 9 , 16 , 30 ] . the level of vo2 at which we observed the lowest value of ve / vo2 , in the individual plot , was the ivt .
the exercise intensity ( speed and slope ) corresponding to ivt was reached by all the subjects . at ivt and at maximal effort ,
in addition , hr ( hr at ivt  hr at rest ) , % hrmax [ ( hr at ivt)/(220  age ) ] , and % hrr [ ( hr at ivt  hr at rest)/(220  age  hr at rest ) ] were also calculated .
based on a previous clinical trial , sample size estimation of 48 subjects achieved 81% power to detect differences among the means versus the alternative of equal means using an f test with a 0.05 significance level .
normal distribution of data was tested by calculating the skewness and kurtosis and by employing the kolmogorov - smirnov test .
the results obtained in the study are expressed as means  standard deviation ( sd ) . to verify that groups did not differ among each other regarding age , weight , height , bmi , and % fm ,
moreover , one - way anova was used to assess differences among groups at maximal effort and at ivt .
differences between groups were evaluated with a multiple unpaired t - test with bonferroni correction .
all statistical analyses were performed with the spss statistical package ( version 20.0 for windows ; spss inc . ,
all tests were two - tailed , with  = 0.05 being taken as significant .
anthropometric measurements were taken as described in the materials and methods section . in particular , age and
further biochemical evaluation showed that glycated hemoglobin was 49.9  8.3  mmol / mol in t2 dm group , while no alterations in glycemic values were found in subjects of the other 2 groups .
as previously mentioned , treadmill protocol started at 3  km / h and then speed increased by 1  km / h every 2 minutes until 5  km / h was reached , while slope was increased by 3% every minute until subjects reached a value of 10 on rpe scale .
the results regarding absolute and relative exercise intensities at maximal effort in obese , sarcopenic obese , and t2 dm subjects are shown in tables 2 and 3 .
the subjects vo2peak ranging from 18.1  ml  min  kg in ob , 16.9  ml  min  kg in so , and 16.7  ml  min  kg in t2 dm groups demonstrate that the subjects were very unfit . in particular , no significant differences were found among the three different groups for any studied variable at maximal effort as shown in table 2 .
all subjects reached ivt and no significant adverse events were observed during the testing session in all groups ( table 2 ) .
interestingly , all the variables at ivt demonstrated significant differences in t2 dm subjects group as compared to the other two groups of obese individuals , as depicted in table 3 . in detail ,
at ivt all the studied variables were significantly lower in t2 dm groups than in ob and os groups indicating that t2 dm subjects had significantly lower exercise capacity at ivt . at ivt
data regarding peak exercise capacity of these subjects showed that they were all very untrained and unfit .
the primary finding of our study was that all the physiological parameters considered for pa at ivt were lower in t2 dm group as compared to ob and so groups , even if at maximal effort no differences were observed among groups .
thus , the results obtained in our study demonstrate the importance of the use of ivt to prescribe aerobic exercise training in different obesity conditions .
t2 dm subjects were obese and they had not practiced any organized pa prior to the enrollment of this study .
moreover , subjects ' fitness parameters , such as vo2peak , showed that they were unfit as previously described for obese population . according to these observations , the use of a constant moderate intensity exercise as training method appears probably more appropriate .
in fact , the american college of sports medicine ( acsm ) pa guidelines for t2 dm subjects recommend performing low - to - moderate intensity pa ( at 4070%  vo2max ) to achieve cardiorespiratory and metabolic improvement . more importantly
, lower intensity activity leads to a more comfortable level of exertion and , likely , enhances the likelihood of adherence . at the same time it might reduce the risk of musculoskeletal injury and feet - ankle trauma , particularly when
, acsm suggests using three variables to monitor exercise intensity : vo2max , hr , and rate of perceived exertion ( rpe ) .
moreover , during the last years , the gas exchange threshold was identified as valid tool to delineate the  training zone  for endurance training and for unhealthy subjects . indeed ,
in fact , vo2peak was ranging from 11.9 to 21.5  ml  min  kg when considering all groups .
moreover during submaximal exercise test subjects did not reach their hrmax ( 220  age ) but they stopped around 75% of their maximal hr .
interestingly , our results demonstrate that when exercise intensity is prescribed according only to relative parameter based upon hrmax ( such us % hrmax or % hrr ) , without adjustment for each individual 's exercise capacity , exercise intensity could be overestimated .
our results , at peak exercise , were not different from those reported by hulens et al .   in obese population confirming a lower physical fitness level in obese subjects .
low vo2peak is in agreement with the literature regarding the cardiorespiratory fitness in obese subjects [ 32 , 33 ] .
.   showed that vo2peak was 15.8  3.8  ml  min  kg in obese women while in the study developed by aiello et al .  
vo2peak in t2 dm subjects was previously described by our group   assessing that vo2peak in t2 dm subjects ranging from 15.9 to 18.6  ml  min  kg .
our obese subjects , either sarcopenic or diabetic , had 16.9  2.9 and 16.7  4.8  ml  min  kg , respectively , demonstrating that vo2peak in so and t2 dm subjects does not differ from obese subjects .
moreover , ventilation and absolute vo2 were very low and no differences were present among groups , which could be explained by the influence of fat mass on respiratory system . even if the impact of obesity on cardiorespiratory fitness is not completely understood , fat mass might affect respiratory and exercise physiology during exercise . respiratory muscle function and lung volumes at rest and during exercise
could be potentially compromised as a result of obesity , influencing the breathlessness perception and the vo2peak values .
in fact , obese individuals show decreased respiratory system compliance , which results in a restrictive ventilatory defect .
vo2peak in t2 dm patients is slightly lower than those previously reported , which could be explained by the younger age of the subjects recruited by belli et al .   as compared to our study . regarding the data of vo2peak in os subjects , the results obtained in our study are the first ever described in such population .
we might speculate that a decrease in muscle mass could have negative effects on vo2peak .
however , there were no differences among the groups , which could be explained by a potential important negative effect of fat mass on vo2peak in adult population .
t2 dm group showed significantly lower results for all physiological parameters regarding exercise capacity at ivt , compared to ob and os groups , suggesting that during exercise t2 dm subjects reach the ivt earlier than ob and os subjects .
the differences between t2 dm group and the other two groups could be justified by the altered substrate utilization of t2 dm subjects .
in fact , it has been shown that t2 dm patients have a greater boost in basal lactate levels than ob subjects . moreover , metz et al
.   showed that basal- and exercise - induced increases of lactate level in t2 dm women were negatively correlated with 2 indexes of substrate utilization ( crossover and maximal fat oxidation points ) .
the crossover point of substrate utilization is defined as the power output at which energy from cho - derived fuels predominates over energy from lipids , with further increases in power eliciting a relative increment in cho utilization and a decrement in lipid oxidation .
differently , maximal fat oxidation point marks the exercise intensity at which the rate of fat oxidation is maximal .
metz et al .   hypothesized that an elevated lactate level could potentially act on substrate utilization by two mechanisms .
first , it is the process of acting by promoting lactate utilization and , in the same way , carbohydrate oxidation .
consequently , t2 dm subjects could have more pronounced carbohydrate utilization during exercise ( lower crossover point ) .
secondly , lactate could inhibit lipid oxidation as already suggested in experimental animal models ( low maximal fat oxidation point ) .
the ivt marks the upper limit after which there is the first in blood lactate concentration that leads to slight rising in carbon dioxide partial pressure with a compensatory increased stimulus for ventilation .
the strong relationship between ventilatory threshold and substrate utilization could justify the lower physiological parameter values at ivt in t2 dm group than in the other two groups .
these results highlight the importance to individualize the exercise intensity according to the individuals ' physiological characteristics .
in fact , t2 dm showed a lower value of exercise intensity corresponding to ivt compared to ob and os groups .
therefore , the specialist physical activity teacher could overestimate the exercise intensity for optimal moderate training if this intensity is evaluated according to relative terms ( % vo2max , % hrmax , etc . ) in conclusion , even if there were no differences between t2 dm and ob and os groups at maximal effort , t2 dm subjects showed a lower exercise capacity at ivt .
the use of ivt should become more frequent in obese individuals , since training at this intensity improves aerobic capacity , cost effectiveness of treatment but might also increase adherence to physical activity in obese subjects .
these novel results highlight the importance to prescribe exercise intensity , according to ivt to avoid the possibility of overestimating exercise intensity in obese subjects with different condition and , thus , we believe that they might be useful for professional figures who work to achieve and maintain fitness in obese population .
 aim of the study was to examine cardiorespiratory parameters at individual ventilatory threshold ( ivt ) and peak exercise capacity ( vo2peak ) in outpatient diabetic and sarcopenic obese subjects . 
 seventeen obese subjects ( bmi : 36.6  4.1  kgm1 ) and sixteen so subjects ( bmi : 37.0  7.3  kgm1 ) were compared with sixteen t2 dm subjects ( bmi : 37.7  5.6  kgm1 ) . 
 all groups performed an incremental exercise test on a treadmill according to their physical ability . 
 vo2peak , % hrmax , and maximal metabolic equivalent ( metmax ) were evaluated at maximal effort . 
 moreover , vo2ivt , % vo2peak , % hrmax , % hrr , hr , and metivt were assessed at ivt . 
 no significant differences were found in any physiological parameters at maximal effort ( vo2peak , % hrmax , and metmax ) in all groups . on the contrary , 
 vo2ivt , % vo2peak , % hrmax , % hrr , hr , and metivt were significantly lower in t2 dm subjects as compared to ob and so subjects at ivt ( p < 0.05 ) . 
 our results show that while at maximal effort there are no differences among groups , at ivt the physiological parameters are lower in t2 dm subjects than in ob and so subjects . therefore , due to the differences observed in the groups , we suggest usng the ivt as a useful parameter to prescribe aerobic exercise in obese with sarcopenia or diabetes mellitus conditions . 
1. Introduction
2. Methods
3. Results
4. Discussion