- During maximal exercise testing below the anaerobic
threshold, VE is linearly related to VO 2 and VCO 2 ,
after which VE/VO 2 increases followed by an increase
in VE/VCO 2. The increase in VE/VCO 2 reflects respi-
ratory compensation for rise in blood lactate.
MAXIMAL HEART RATE
- The highest HR achieved during a standardized max-
imal exercise testing is the maximal HR. If an exercise
test is not possible, then age-predicted heart-rate for-
mulas can be used. Two formulas used are: Maximal
HR =220 – age or208 – 0.7 ×age. - The first formula has been used for many years and the
second was only recently developed. This new formula
may be more accurate for older persons and is inde-
pendent of gender and habitual physical activity
(Tanaka, Monahan, and Seals, 2001). It is important to
note that an estimated maximal HR may be 5 to 10%
(10 to 20 bpm) higher or lower than the actual value. - Maximal HR differs for various activities, since it is
influenced by body position and amount of muscle
mass involved.
HEART RATE RESERVE
- The difference between maximal HR during maximal
exercise testing and resting HR is the heart rate reserve
(HRR). If maximal HR is 205 bpm and resting HR is
55 bpm, then HRR would be 205 – 55 =150 bpm. The
smaller the difference, the lower the reserve and the
narrower the range for exercising.
TARGET TRAINING HEART RATE
•A training program requires calculating a target heart
range. To calculate the lower and upper target heart
rates, 60–90% of maximal heart rate or 50–85% of
heart rate reserve can be used. For the first, 60 and
90% of maximal HR will be determined as: 0.60×
Maximal HR (bpm) and 0.90×Maximal HR (bpm).
•For the second method or Karvonen formula, which
may be a more appropriate and valid approach, 50 and
85% of HRR is used: 0.50 ×HRR +resting HR and
0.85 ×HRR +resting HR.
MUSCULAR CONTRACTIONS
ISOMETRIC/STATICCONTRACTIONS
- Isometric contractions refer to muscle fiber recruit-
ment wherein no change in fiber length takes place: no
joint or limb motion occurs. Examples of isometric
contractions are a person holding a weight in a partic-
ular position and postural stability.ISOTONIC/DYNAMICCONTRACTIONS- Isotonic contractions are when muscle fibers change
length and no movement at joints occurs. Specific
types of dynamic contractions include concentric,
eccentric, andisokinetic. - Concentric contractions are movements where the
muscle fibers shorten as the muscle contracts, such as
when a weight is being lifted. This is also known as
positive work. - When the direction is reversed and the weight is low-
ered, the contraction becomes an eccentric contrac-
tion (negative work), where muscle fibers lengthen as
the muscle contracts. More fast-twitch motor units are
activated during eccentric contractions.
ISOKINETICCONTRACTIONS- Isokinetic machines make these contractions possible:
the muscular movement is performed at constant
speed against a variable resistance. The applied resist-
ance during the contraction is increased or lowered at
various points across the full range of motion so a
constant speed of movement can be maintained.
Diagnostic strength equipment use isokinetic tension,
so more accurate measures of strength can be made at
varying joint angles.
BORG SCALE OR RATING OF
PERCEIVED EXERTION•A Borg scale or rating of perceived exertion(RPE)
scale is for an individual to rate his or her own “degree
of physical strain” (Table 8-4). The original Borg
scale ranges from 6 to 20, with each number anchored40 SECTION 1 • GENERAL CONSIDERATIONS IN SPORTS MEDICINE
TABLE 8-4 The Original and New Borg Scales for Rating
of Perceived Exertion
ORIGINAL SCALE NEW SCALE
6 No exertion at all 0 Nothing at all
7 Extremely light 0.5 Very, very weak
81 Very weak
9Very light 2 Weak
10 3 Moderate
11 Light 4 Somewhat strong
12 5 Strong
13 Somewhat hard 6
14 7 Very strong
15 Hard (heavy) 8
16 9
17 Very hard 10 Very, very strong
18 * Maximal
19 Extremely hard
20 Maximal exertion