Human Energy

Types of Human Energy

§    Aerobic – involves the use of oxygen to derive needed fuel for exercise performance


§    Anaerobic – involves non-oxygen sources to derive needed energy for exercise performance

Basic Unit of Energy

§    ATP = adenosine triphosphate





In order to get energy from ATP, a phosphate must be broken off by H20


Anaerobic Energy

§    ATP

§    Phosphocreatine  (PC or CP)

§   Helps rebuild ATP from ADP

§   It is important because only a small amount of ATP can be maintained within the cell at  one time.

§   Only about 80-100 grams of ATP are stored in the body at one time

§   This is enough energy for several seconds of all-out effort (5-8 seconds)

Can the body be trained to store more ATP?

§    Yes

§    How?

§   Performing high intensity activity of 6-10 sec duration in repeated intervals

§   Prompts the muscle to increase the quantity of high-energy phosphates, i.e. ATP and CP

§   Supplementation with creatine phosphate has been shown to increase CP in the muscle. However, it is unclear as to the true benefit.

Important Energy Reactions

§     Anabolic – building energy stores

§    Glucose+Glucose                             Glycogen

§    Glycerol+Fatty Acids                                Triglyceride

§    Amino Acids+Amino Acids                       Protein


§     Catabolic – breaking down ATP for energy

§    Glycogen                                     Glucose

§    Triglyceride                               Glycerol + Fatty acids

§    Protein                                     Amino acids

Important Anaerobic Energy Generating Process

§       Glycolysis – occurs in the watery medium of the cell (cytoplasm)

§      Glucose

             (-ATP)    G6P


                                              (-ATP)  F1,6P



                                                          3 PGAld                  3 PGAld

                                             (+NADH)                                       (+NADH)

                                                      1,3 PGAte                1,3 PGAte

                                                (+ATP)                                       (+ATP)

                                                         3 PGAcid                         3 PGAciid


                                                            2 PGAcid                      2 PGAcid


                                                            2 PhosEnolPyr         2 PhosEnolPyr

                                                 (+ATP)                                       (+ATP)

                                                               Pyruvate                  Pyruvate


                                                           Lactate                     Lactate


      Net  gain of 2 ATP (from glucose)

      Net  gain of  2 NADH

      Glycolysis releases only 10% of the energy of a glucose molecule

Important Aerobic Process

§     From glycolsis, pyruvate moves toward mitochondria and converts to acetyl-CoA


Important Aerobic Process

§       NADH’s and FADH’s are transferred to Electron Transport Chain (in mitochondria)













Summary of ATP Generated from Glucose

§     Glycolysis = 2 net ATP

                       = 4 net ATP from NADH


§     Pyruvate      Acetyl CoA = 6 net ATP

§     Kreb’s Cycle = 2 net ATP

§     Electron Transport Chain = 22 net ATP


§     Total = 36 ATP



Energy from Fat

§    Fat represents most plentiful source of potential energy in the body

§   Comparison fuel source reserves:

§   Fat amount in adipose tissue = 60,000-100,000 kcals
§                     in muscle            = 3,000 kcals
§   Glycogen amount in muscle/liver = 2,000 kcals

How does adipose tissue  become available for energy?

§     Adipose tissue

                                      fatty acids diffuse into                                                       blood

       Carried by albumin

          to muscle

                                      Taken up by muscle

                                          1. for energy

                                          2. for storage in muscle

How is fat converted to ATP in muscle?

§      Fatty acids enter mitochondria


            Converted to acetyl-CoA via B-

                             oxidation process


                        Acetyl-CoA enters Krebs Cycle

                                    (just like with glucose



                                    NADH’s and FADH’s formed and enter

                                           Electron Transport Chair (just like with

                                             glucose breakdown)



Pictorial View of Fat Metabolism

§     Triglyceride from blood

Typical Summary of ATP’s generated from Fat

Source               Pathway                  ATP’s

1 molecule          Glycolysis +               19

   of glycerol          Kreb’s Cycle


3 molecules        Beta-oxidation +        441

of  18-C F.A.         Kreb’s Cycle

                                                 Total= 460

Fat Contribution to Exercise

§     Low Intensity – fat is primary contributor to energy needs for exercise

§     Moderate Intensity – fat contributes 50% and CHO contributes other 50%

§     High Intensity – CHO is primary contributor to energy needs


§     Long-duration beyond 1 hour of exercise duration, fat can contribute up to 80% of energy needs

How do we know which fuel source we’re using with exercise?

§      The R value

§     Equals amount of CO2 expired

                                        O2 consumed

§     If we expire more CO2, primarily burning carbohydrates

§     If we consume more O2, primairly burning fats


§     For example, if we are at a low level of exercise intensity, it is easy to breathe in O2.. Our ability to burn fat is easier.  This gives a R value of ~.70


§     For example, if we are at a high level of exercise intensity, it is difficult to breathe in O2.  We need to depend on CHO to get our energy and hence a large production of CO2.  This gives a R value of ~ 1.0


§      R value measured on metabolic energy system

Fat-buring Adaptations within Skeletal Muscle following Aerobic Training

§    Faster breakdown and build-up ability in adipose tissue

§    Greater # and density of capillaries

§    Improved transport of FFA into and within skeletal muscle

§    Increase in size and # of mitochondria

§    Increase in amount of aerobic enzymes in Kreb’s Cycle and ETC

Energy Can be Supplied from Protein

1) Amino Acid



2) Amino Acid            



3) Amino Acid

What Interconversions can occur between the Macronutirents?

Acid-Base Regulation in Body During Exercise

§     Definitions:

§    Acid = substance that releases H+ ions

§    Base = substance that picks up H+ ions

§     Body attempts to maintain a pH balance between acid and base such that it stays around 7.0-7.4

§     Exercise can decrease pH by lactic acid accumulation resulting in fatique

§    Body buffers change through sodium bicarbonate


Can we improve exercise performance by taking sodium bicarbonate?

§    Research suggests that high-intensity, short term exercise performance may be enhanced by sodium bicarbonate (or sodium citrate) ingestion

        e.g. 800-meter race times can be

                improved by ~3 seconds.

§    IOC does not currently ban alkalinizing agents