A MODIFIED YMCA BENCH PRESS TEST TO PREDICT STRENGTH IN ADULT WOMEN
by
Linda Cosgrove and Jerry Mayhew
Kirksville College of Osteopathic Medicine, Kirksville, MO
and Truman State University, Kirksville, MO

Original Publication Information:
IAHPERD Journal Volume 30. No.2 Spring, 1997.
INTRODUCTION
For those involved in fitness evaluation, the search for the best measurement techniques is an on-going process. While strength may be one of the more fundamental aspects of a complete fitness profile, its measurement is far from simple. The most widely accepted technique for evaluating strength is probably the one repetition-maximum (1-RM) in which the most weight that can be lifted once through a full range of motion is determined.

Because of the increased possibility of injury using a maximal effort technique in untrained individuals, various prediction methods using submaximal loads have been suggested. The YMCA test was adopted in an attempt to evaluate strength and muscular endurance using a relatively light load (Golding, Myers & Sinning, 1982). The test requires a male to lift 80 lbs and a female to lift 35 lbs as many times as possible. The test is terminated when the individual cannot completely extend the elbows during a lift or cannot keep pace with a metronome set at 60 beats/minute.

While it is suggested that a free-weight barbell be used for the test, not all facilities have such equipment. In addition, for novice lifters, machine weights add a degree of security that may allow them to perform nearer to maximum levels. The purpose of this study was to determine the accuracy of using repetitions-to-fatigue (RTF) on a machine weight apparatus to predict 1-RM bench press strength in adult women.

METHODS
Fifty-one female medical students and medical college employees volunteered to participate during their annual fitness evaluation. Each subject had been given medical clearance to participate by a physician.

Initially each subject performed as many repetitions as possible on a Universal Gym variable-resistance bench press machine using 18.2 kg (40 lbs). This was the lowest setting possible on this apparatus, and all subjects were capable of completing at least several repetitions with that load. Although a metronome was not used to set the cadence, each subject was instructed not to pause longer than 2 seconds during the lifting motion.

Within 10 days following the absolute muscular endurance task, each subject performed a 1-RM bench press test using the same apparatus. The lift was begun in the bottom position and judged successful when the arms were fully extended. Three to five minutes rest was allowed between attempts to avoid fatigue. Each subject reached her 1-RM within 3 to 6 attempts.

RESULTS
The physical characteristics of the subjects are shown in Table 1. The range for the RTF showed a great deal of variability, from a low of 8 to a high of 105. Assuming 2 seconds for each repetition, the RTF required an average of approximately 3 mins to complete, with the longest being 7 mins.

The RTF had a slightly higher correlation with LBM than with body mass (Table 2). None of the lifting parameters was significantly correlated with %fat.

Multiple regression analysis was used to develop prediction equations unique to this device and population. The following equations were produced:

1-RM (kg) = 18.1 + 0.34 Reps (1)
1-RM (kg) = 10.1 + 0.31 Reps + 0.14 Body Mass (kg) (2)
1-RM (kg) = 6.6 + 0.30 Reps + 0.26 LBM (kg) (3)

The multiple correlations were R = 0.81, 0.85, and 0.85, accounting for 65.6%, 68.9%, and 68.9% of the explained variance, respectively. The SEE for each equation was 5.0 (11.0 lbs), 4.6 kg (10.1 lbs), and 4.6 kg (10.1 lbs), respectively.

Two previous studies have developed 1-RM predictions equations for the YMCA test, one using free weights (Rose & Ball, 1992) and one using a Nautilus leverage bench (Kraus, Mayhew, Nicholls, Russell, Johnson, Sweeney & Sloop, 1996). The free weight predictions using reps and/or body weight significantly overpredicted 1- RM in the current subjects by 34.1% and 36.9% (Rose & Ball, 1992). The machine weight predictions using reps and/or body weight overpredicted 1-RM by 45.4% and 66.2% (Kraus et al., 1996).

Table 1. Physical Characteristics Of The Subjects (n= 51).
Varable Mean SD Range
Age(y) 26.0 4.3 22.0 - 45.0
Height (cm) 166.8 6.1 154.9 - 180.3
Weight (kg) 65.3 14.9 49.1 - 133.6
LBM (kg)(cm) 51.4 8.5 41.0 - 86.2
% Fat 20.5 4.7 12.7 - 35.5
1-RM (kg) 33.1 8.4 18.2 - 59.1
1-RM/kg 0.52 0.13 .029 - 0.95
Rep wt/1-RM 0.58 0.14 0.31 - 1.00
Reps 44.1 20.0 8 - 105

Table 2. Correlations Among Variables.
Varable 2 3 4 5 6
1. Weight (kg) 0.97 0.76 0.07 0.30 0.48
2. LBM (kg) 0.59 0.06 0.36 0.52
3. % Fat 0.02 0.02 0.16
4. Rep Wt (kg) - 0.16 - 0.09
5. Reps 0.81
6. 1-RM (kg)


DISCUSSION
Typically individuals will be able to do more RTF on a machine weight device than with free weights (Kraus et al., 1996). While the use of lifting machines may increase the amount achieved in the 1-RM, they do not alter the relationship between 1-RM and RTF (Bates, Bowen, Mayhew & Visich, 1995). The failure of the current values to cross-validate other equations developed with either free weights or machine weights may signal a note of caution for strength prediction.

Although the current subjects lifted 16.0% less in the 1-RM than college females using free weights (Rose & Ball, 1992), they were able to do 32.0% more RTF with this device. Perhaps strength and muscular endurance measurements are device-specific, although previous research has indicated this is not likely (Kraus et al., 1996). Other machine weights will need to be evaluated before this speculation can be solidified. Until that time, care should be taken in interchanging free weights and machine weights to estimate strength from RTF.

REFERENCES