:: w 60 Plasma FFA % $ 40 5 ii 20 s B loo t Time Fig. 9. Relative contribution of blood-borne an

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70% VO2maxでの運動時のエネルギー源。運動の後半で筋肉グリコーゲンが減少したときは、摂取した炭水化物が血糖値を維持し、主要な炭水化物エネルギー源となる。 Coyle 1992 ％エネルギー消費量運動時間(時間) 血糖値維持される必要あり脂肪血中ブドウ糖筋肉グリコーゲン

(2)

Romijn JA et al (1993)

SUBSTRATE UTILIZATION DURING EXERCISE E387

3oo f/$j Muscle Glycogen • l Muscle Triglycerides q Plasma FFA q Plasma Glucose v- 25 65 % of V02 max 85

Fig. 8. Maximal contribution to energy expenditure derived from glucose and FFA taken up from blood and minimal contribution of muscle triglyceride and glycogen stores after 30 min of exercise, expressed as function of exercise intensity. Total amount of calories (Cal) available from plasma does not change in relation to exercise intensity.

:: w 60 Plasma FFA % $ 40 5 ‘ii 20 s 0 -15 30 45 60 75 90 105 120 B loo t 15 30 45 60 75 90 105 120 Time (mln)

Fig. 9. Relative contribution of blood-borne and intramuscular substrates to energy production during 120 min of exercise at 25% Voz maX (B) and 65% (A) VO, mBx. Tg, triglycerides.

lipolysis was high during low-intensity exercise and did not increase further with more intense exercise. However, little lipolysis of muscle triglycerides occurred during low- intensity exercise (i.e., 25% Vo, ,,,) compared with exercise at the higher intensities. Despite high lipolytic rates, the R, of plasma FFA, and presumably oxidation, was highest during exercise at 25% Vo, max, and FFA R, declined progressively as the exercise intensity increased to 65 and 85% 00, ,,,Bx. The progressive decline in plasma

Table 2. Plasma concentrations of catecholamines

at rest, during exercise, and after 60 min of recovery

Exercise Intensity,

% iTo max Rest

Exercise, min _Recovery

30 120 (60 min) 25 65 85 25 65 Epinephrine 38rt6 59+3* 52+8* 36+4 58217 199+18*t 239+28*t 62ztl7 36+7 625+86*$ 4428 Norepinephrine 231rt43 388+54* 372+41* 223+27 291+31 1,694+237*t 1,851&286*t 424+130 85 266219 5;085+914*$ 293+52

Values are means rt SE in mg/l. * P < 0.05 vs. rest. t P < 0.05 vs. exercise at 25% of ~osmax.

vo2 max.

$ P-C 0.01 vs. exercise at 25 and 65% of

FFA turnover with increasing exercise intensity was off- set by progressive increases in blood glucose turnover. Therefore the contribution of plasma substrates to ca- loric expenditure remained essentially constant over this wide range of exercise intensities. The changes in lipid

metabolism occurred concurrently with changes in carbohydrate metabolism, consistent with what would have been predicted from previous work, namely that glucose tissue uptake and especially muscle glycogen utilization

increased roughly exponentially in relation to exercise intensity.

Evaluation of Methods

The use of stable isotope tracers for quantification of glucose and palmitate turnover is well established (35). Whole body oxidation rates of fat and carbohydrate were calculated by indirect. calorimetry. This method relies on the assumption that VO, and VCO~ accurately reflect tissue 0s consumption and COB production (14). There is little controversy with respect to VO,, of which there are no large stores in the body. However, at exercise intensities that cause hyperventilation, VCO~ may overestimate tissue CO2 production (13). This can potentially result in the overestimation of the rate of carbohydrate oxidation and, concomitantly, an underestimation of fat oxidation

(13). Therefore, before the present study, we conducted a preliminary study that developed a new breath 13C-toJ2C ratio method for the calculation of carbohydrate and fat oxidation during exercise at low to high intensities that is completely independent of the measurement of VCO~ (26). This new method proved that carbohydrate and fat oxidation calculated by indirect calorimetry during exercise is valid, including during exercise at 85% VO, max in trained subjects, as performed in the present study.

The rates of fat and carbohydrate oxidation in excess of the measured blood glucose and plasma FFA uptake are assumed to equal the oxidation of intramuscular triglyceride and glycogen, respectively. There is no reason to believe that there are major fates other than oxidation for glucose and FFA taken up by the tissues during exercise

(6, 17). The maximal rate of FFA oxidation from periph- eral lipolysis can thus be considered to be equal to plasma FFA uptake. The difference between that rate and total fat oxidation can be attributed largely to intramuscular

筋肉グリコーゲン

筋肉脂肪

血中遊離脂肪酸

血中ブドウ糖

筋肉脂肪

血中遊離脂肪酸

血中ブドウ糖

低強度の運動

中強度の運動

運動強度が高くなると炭水化物エネルギーの消費が増える

(3)

Van Loon LJ et al (2001) J Physiol 536:295–304

(Table 1), implying that plasma FFA oxidation has been overestimated in the past, and conversely that TG oxidation has been underestimated. Furthermore, the data show that the contribution of plasma FFA and TG fat sources was about 50 % each at each exercise intensity. We also correctly assumed that total fat oxidation minus plasma FFA oxidation equals the sum of intramuscular plus lipoprotein-derived TG oxidation, while others (e.g.

Romijn et al. 1993, 1995; Sidossis et al. 1997), for reasons

that are not immediately obvious, excluded lipoprotein-derived TG as an important energy source during exercise. Finally, we have recently validated the assumption that the Rd of glucose equals its oxidation rate during

moderate- to high-intensity exercise (Jeukendrup et al.

1999), indicating that our estimates of blood glucose and muscle glycogen oxidation are about equal to those

published previously (Romijn et al. 1993).

In order to eliminate day-to-day variations, we quantified substrate utilisation at different exercise intensities within a single trial. Furthermore, we investigated possible accumulative effects of the incremental protocol on substrate utilisation by asking four of the subjects to perform three additional single trials at 40, 55 and 75 %

Wmax. There were no differences in total fat and

carbohydrate oxidation rates when comparing these single trials with the incremental protocol. The relative

decrease in fat oxidation at 75 % W_max tended to be even

greater when the subjects started exercise at the high-intensity workload immediately after warming up. This indicates that emptying of the intramuscular TG stores did not seem to play a role in the reduction of fat

oxidation observed at 75 % W_max.

In the present study, total fat and carbohydrate oxidation rates increased from rest to exercise (Table 2).

However, the relative contribution of fat oxidation to total energy expenditure did not change from resting conditions to exercise, and remained unchanged when

exercise was increased up to 55 % Wmax (Fig. 4). No

significant changes were found in the relative contribution of the different substrate sources to total energy expenditure. However, as exercise intensity was

further increased up to 75 % Wmax, substrate utilisation

changed markedly. Total body fat oxidation rate

decreased by 34 ± 7 % compared to that at the 55 % Wmax

workload (P < 0.05), and this was accounted for by a

reduction in the oxidation rate of plasma FFAs and of other fat sources (i.e. the sum of intramuscular and lipoprotein-derived TG; Table 2 and Fig. 4). A reduction in plasma FFA availability did not seem to play a role in reducing fat oxidation rates, as Ra palmitate (Table 1) and the plasma concentrations of palmitate (Fig. 1) and total FFAs (Fig. 3) did not decrease significantly at the highest workload. As blood flow will have been greatest at the highest exercise intensity, this implies that the arterial FFA supply will also have been greatest at this

time. In contrast to our data, Romijn et al. (1995)

observed a significant reduction in Ra palmitate during high-intensity exercise, which may be explained by the fact that they applied a slightly higher (relative) workload. However, elevation of plasma FFA availability by lipid and heparin infusion only partially restored fat

oxidation at the highest exercise intensity (Romijn et al.

1995). Therefore, both studies indicate clearly that the observed decrease in total fat oxidation cannot be accounted for by a decreased plasma FFA availability

and that the ‘glucose–FFA cycle’ (Randle et al. 1963) does

not operate during high-intensity exercise.

Suggestions have also been made that the transport of FFAs across the plasma membrane limits FFA uptake

Exercise intensity and fuel source utilisation

J. Physiol. 536.1 ₃₀₁

Figure 4. Energy expenditure and fuel selection

Values are means. FFA, free fatty acid.

) at Osaka Taiiku University on July 6, 2011

jp.physoc.org

Downloaded from J Physiol (

血中ブドウ糖血中遊離脂肪酸筋肉グリコーゲンその他の脂肪運動強度エネルギー消費量

運動時のエネルギー基質(白人)

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Janyacharoen T et al. Eur J Appl Physiol (2009) 107:645-65

エネルギー源の酸化速度

運動強度 (% VO2max)

タイ人のエネルギー代謝

炭水化物の利用が多い

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女性は男性よりも脂肪の利用が多い(白人)

（最大酸素摂取量の60％での90分間の運動中に利用されたエネルギー源）

Carter SL et al. (2001) Am J Physiol Endocrinol Metab 280:E898–E907

Exercise trial (90-min). By design, the percentage of

V˙

O_{2 peak}

elicited in the REL exercise trial was not

different from that elicited in the PRE-training

exer-cise trial, yet the absolute power output (in W) was

higher. Oxygen consumption (V˙

O₂

) was greater in the

REL exercise trial compared with both the PRE and

ABS trials (Fig. 1A). At 75 and 90 min, V˙

O₂

was lower

for the ABS compared with PRE trial (P

0.001)

despite the workloads being the same (Fig. 1A).

Fe-males had a lower absolute V˙

O₂

during the exercise

trial compared with males (Fig. 1B). Endurance

train-ing resulted in a lower RER in the ABS trial, but not in

the REL trial, compared with PRE (P

0.001). RER

increased from rest at the onset of exercise in all

exercise trials (Fig. 1C), and females had a lower

exer-cise RER compared with males (P

0.01; Fig. 1D).

Heart rate was lower during exercise in the ABS trial

compared with both the PRE and REL trials (P

0.001; data not shown). Resting heart rate was

signif-icantly lower after endurance training in both the ABS

and REL compared with the PRE trial (P

0.001; data

not shown). Males had a lower resting heart rate

com-pared with females (P

0.05; data not shown).

Endurance training resulted in an increase in the

proportion of fat oxidized during exercise at the same

ABS workload (P

0.01); however, the proportion of

fat oxidized at the same REL intensity was not affected

by training. Consequently, training resulted in a

de-crease in the proportion of CHO oxidized during

exer-cise at the same ABS (P

0.01), but not REL, intensity

(Fig. 1E). Females oxidized a greater percentage of

energy from fat during exercise compared with males

(P

0.001; Fig. 1F); conversely, males oxidized a

higher percentage of CHO compared with females

dur-ing exercise in all trials (P

0.01; Fig. 1F).

Plasma lactate concentration was lower during

exer-cise (P

0.001) in the ABS trial compared with both

the PRE and REL trials (Fig. 2F). Plasma lactate

Fig. 1. Oxygen consumption (V˙

O₂

),

respira-tory exchange ratio (RER), and substrate

ox-idation. A: V˙

O₂

during 90 min of exercise

before (PRE) and after [absolute (ABS) and

relative (REL)] training.

a

_{Significantly}

differ-ent from PRE and ABS (P

0.001);

b

signifi-cantly different from PRE (P

0.001). B:

gender difference in V˙

O₂

during 90 min of

exercise.

c

_{significantly different from males}

(P

0.001). C: RER during 90 min of exercise

before (ABS) and after (ABS and REL)

train-ing. Main effect for condition:

d

_P

_0.01

(ABS

PRE and REL). D: gender difference

in RER during 90 min of exercise. Main effect

for gender:

e

_P

_{0.01 (females}

_{males). E:}

effect of training on the proportion of

sub-strate utilized during 90 min of exercise.

Main effect of condition:

d

_P

_{0.01 (ABS}

PRE and REL);

f

_P

_{0.001 (ABS ⇥ PRE and}

REL). F: gender differences in the proportion

of substrate utilized during 90 min of

exer-cise. Main effect for gender:

e

_P

_0.01

(fe-males

males);

g

_P

_{0.001 (males}

fe-males).

E901

GENDER AND METABOLISM DURING EXERCISE

on July 6, 2011

ajpendo.physiology.org

Downloaded from

男性

女性

たんぱく質

脂質

炭水化物

%エネルギー消費量

(6)

運動強度 (% VO2max) 脂質炭水化物男性女性 %エネルギー消費量 %エネルギー消費量

タイ人のエネルギー代謝

炭水化物の利用が多く性差はない

Janyacharoen T et al. (2009)

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366 運動生理学的研究I

68.糖質食あるいは脂肪食を長期間摂取したラットにおける持久運動中のエネルギー代謝とグリコーゲン・ローディングの効果

Effects of long-term feeding of carbohydrate diet or fat diet on the glycogen loading and energy metabolism during execise in rats

glycogen loading dietary composition

rat

○岡村浩嗣、菊地範昭、田口優子(大塚製薬(株)佐賀研究所)

•› KOJI OKAMURA, NORIAKI KIKUCHI, YUKO TAGUCHI (Saga Reserch Institute, Otsuka Pharmaceutical Co.Ltd.)

持久的運動能力の向上には、運動開始時に組織グリコーゲン貯蔵量が多いことと、運動中に脂肪を利用してグリコーゲンの枯渇を防止することが重要と考えられている。ところで、運動中に利用される糖と脂肪の割合は種々の要因によって影響されることが知られているが、日常摂取する食事の組成もそのひとつと考えられる。また、持久力向上のための栄養処方であるグリコーゲン・ローディングの効果に対しても、日常の食事組成が影響する可能性がある。そこで本研究では、脂肪食あるいは糖質食を長期的に摂取したラットを用いて、持久的運動中のエネルギー代謝とグリコーゲン・ローディングの効果について検討した。 <方法> Sprague・Dawley系〓ラットを離乳直後から糖質食(タンパク質20%、糖質69%、脂肪11%、カロリー%)あるいは脂肪食(タンパク質20%、糖質1 %、脂肪79%)で7週間飼育した。7週間飼育後、

FIG. 1 TIE EFFECT OF F7mtCISE ON TIE TISSIE GLYQOGEN DONTFRTS OF RATS FED 010 OR FAT DIET FOR 71915.

Mean±SE

*, ** ; sigai f icxntly different between two groups by t-test (*;p<0.05 **<O.01) 各群の約半数のラットを1時間の遊泳運動の前後で屠殺した。残りのラットには2時間の遊泳運動を負荷してグリコーゲンを枯渇させた後高糖質食を給与し、翌日1時間の遊泳運動の前後で屠殺した。 <結果> 脂肪食を7週間摂取することによって、運動開始時の肝及びヒラメ筋のグリコーゲンは減少した。しかし、1時間の遊泳によるグリコーゲンの減少は糖質食群で多かった(図1)。また、一度枯渇したグリコーゲンの肝及びヒラメ筋への再補充は、脂肪食群に高糖質食を与えたときの方が速やかだった。さらに、このようにして再補充されたグリコーゲンの運動中の利用は、脂肪食群で節約される傾向にあった。(図2)。以上のことは、日常摂取する食事の組成が持久運動中のエネルギー代謝やグリコーゲン・ローディングの効果に対して影響することを示唆していると思われる。

FIG. z TIE FExr OF (LYOGEN IAIDIIG ON GLYQ)G 4 UTILIZATION OF RATS FED QI)OR FAT DIET FOR 7 *E13 INKING E RCISE.

Metn•}SE

*, ** ; sigiificantiy different bet*een two sroi s by t-test (* ; p <O.( , ** <O.O1)

岡村ら

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